Patent Application
20220249697
Precise genome targeting technologies using the CRISPR/Cas9 system have recently been explored in a wide range of applications, including gene therapy. A major limitation to the application of Cas9 and Cas9-based genome-editing agents in gene therapy is the size of Cas9 (>4 kb), impeding its efficient delivery via recombinant adeno-associated virus (rAAV).
Point mutations represent the majority of known pathogenic human genetic variants1. To enable the direct installation or correction of point mutations in living cells, base editors (or “nucleobase editors”) were developed, which are engineered proteins that directly convert a target base pair to a different base pair without creating double-stranded DNA breaks2-4. Cytidine base editors (CBEs) such as BE4max3,5-7 catalyze the conversion of target C.G base pairs to T.A, while adenine base editors (ABEs) such as ABEmax4,6 convert target A.T base pairs to G.C. While CBEs and ABEs are both widely used and work robustly in many cultured mammalian cell systems2, the efficient delivery of base editors into live animals remains a challenge, despite promising initial studies8-10. A major impediment to the delivery of base editors in animals has been an inability to package base editors in adeno-associated virus (AAV), an efficient and widely used delivery agent that remains the only FDA-approved in vivo gene therapy vector11. The large size of the DNA encoding base editors (5.2 kb for base editors containing S. pyogenes Cas9, not including any guide RNA or regulatory sequences) precludes packaging in AAV, which has a genome packaging size limit of ≤5 k12,13.
To bypass this packaging size limit and deliver base editors (or “nucleobase editors”) using AAVs, a split-base editor dual AAV strategy14,15 was devised, in which the CBE or ABE is divided into an N-terminal and C-terminal half. Each nucleobase editor half is fused to half of a fast-splicing split-intein. Following co-infection by AAV particles expressing each nucleobase editor-split intein half, protein splicing in trans reconstitutes full-length nucleobase editor. Unlike other approaches utilizing small molecules16 or sgRNA17 to bridge split Cas9, intein splicing removes all exogenous sequences and regenerates a native peptide bond at the split site, resulting in a single reconstituted protein identical in sequence to the unmodified nucleobase editor.
Split-intein CBEs and split-intein ABEs were developed and integrated into optimized dual AAV genomes to enable efficient base editing in somatic tissues of therapeutic relevance, including liver, heart, muscle, retina, and brain. The resulting AAVs were used to achieve base editing efficiencies at test loci for both CBEs and ABEs that, in each of these tissues, meets or exceeds therapeutically relevant editing thresholds for the treatment of some human genetic diseases at AAV dosages that are known to be well-tolerated in humans. By integrating these developments, dual AAV split-intein nucleobase editors were used to treat a mouse model of Niemann-Pick disease type C (e.g., type C1), a debilitating disease that affects the central nervous system (CNS), resulting in correction of the casual mutation in CNS tissue, and an increase in the animal's lifespan. In addition, dual AAV split-intein nucleobase editors were used to treat a mouse model of congenital deafness, resulting in correction of the casual mutation in vivo.
Accordingly, in some aspects, described herein are nucleic acid molecules, compositions, recombinant AAV (rAAV) particles, kits, and methods for delivering a Cas9 protein or a base editor (or “nucleobase editor”) to cells, e.g., via rAAV vectors. Typically, a Cas9 protein or a nucleobase editor is “split” into an N-terminal portion and a C-terminal portion. The N-terminal portion or C-terminal portion of a Cas9 protein or a nucleobase editor may be fused to one member of the intein system, respectively. The resulting fusion proteins, when delivered on separate vectors (e.g., separate rAAV vectors) into one cell and co-expressed, may be joined to form a complete and functional Cas9 protein or nucleobase editor (e.g., via intein-mediated protein splicing). Further provided herein are empirical testing of regulatory elements in the delivery vectors for high expression levels of the split Cas9 protein or the nucleobase editor.
Some aspects of the present disclosure provide nucleic acid molecules encoding a N-terminal portion of a nucleobase editor fused at its C-terminus to a first intein sequence, wherein the nucleic acid molecule is operably linked to a first promoter, further comprising a nucleic acid segment encoding a guide RNA (gRNA) operably linked to a second promoter, wherein the direction of transcription of the nucleic acid segment is reversed relative to the direction of transcription of the nucleic acid molecule. Further provided are nucleic acid molecules encoding a C-terminal portion of a nucleobase editor fused at its N-terminus to a second intein sequence, wherein the nucleic acid molecule is operably linked to a third promoter, and further comprising a nucleic acid segment encoding a guide RNA (gRNA) operably linked to a fourth promoter, wherein the direction of transcription of the nucleic acid segment is reversed relative to the direction of transcription of the nucleic acid molecule.
In some embodiments, the disclosed nucleic acid molecules further comprise i) a transcriptional terminator, optionally wherein the transcriptional terminator is the transcriptional terminator from a bGH gene, hGH gene, or SV40 gene, and ii) a woodchuck hepatitis posttranscriptional regulatory element (WPRE) inserted 5′ of the transcriptional terminator. In certain embodiments, the WPRE is a truncated WPRE sequence. In certain embodiments, the truncated WPRE sequence comprises W3, as first reported in Choi, J. H., et al. (2014), Mol. Brain 7: 17, incorporated by reference herein. In certain embodiments, the WPRE is a full-length WPRE. In certain embodiments, the first and/or third promoters comprise a Cbh promoter. In certain embodiments, the second and/or fourth promoters comprise a U6 promoter.
Other aspects of the present disclosure provide compositions comprising: (i) a first nucleotide sequence encoding a N-terminal portion of a Cas9 protein fused at its C-terminus to an intein-N; and (ii) a second nucleotide sequence encoding an intein-C fused to the N-terminus of a C-terminal portion of the Cas9 protein, wherein at least one of the first nucleotide sequence and second nucleotide sequence is operably linked to a first promoter, wherein at least one of the first nucleotide sequence and second nucleotide sequence comprises at its 3′ end a gRNA nucleic acid segment encoding a guide RNA (gRNA) operably linked to a second promoter, and wherein the direction of transcription of the gRNA nucleic acid segment is reversed relative to the direction of transcription of the at least one nucleotide sequence.
In some embodiments, the Cas9 protein is a catalytically inactive Cas9 (dCas9) or a Cas9 nickase (nCas9), and wherein the first nucleotide sequence of (i) and/or the second nucleotide sequence of (ii) further comprises a nucleotide sequence encoding a nucleobase modifying enzyme fused to the N-terminus of the N-terminal portion of the Cas9 protein.
In some embodiments, the nucleobase modifying enzyme (or nucleobase modification domain) is a deaminase. In some embodiments, the deaminase is a cytosine deaminase. In some embodiments, the deaminase is an adenosine deaminase. In some embodiments, the second nucleotide sequence of (ii) further comprises a nucleotide sequence encoding a uracil glycosylase inhibitor (UGI) fused at the 3′ end of the second nucleotide sequence. In some embodiments, the first nucleotide sequence of (i) further comprises a nucleotide sequence encoding a uracil glycosylase inhibitor (UGI) at the 5′ end of the first nucleotide sequence. In some embodiments, the UGI comprises the amino acids sequence of SEQ ID NOs: 299-302.
In some embodiments, the first nucleotide sequence and the second nucleotide sequence are on different vectors. In some embodiments, the each of the different vectors is a genome of a recombinant adeno-associated virus (rAAV). In some embodiments, each vector is packaged in a rAAV particle. In some aspects, the present disclosure provides rAAV particles comprising a first nucleic acid molecule (e.g. encoding a N-terminal portion of a nucleobase editor or Cas9 protein fused at its C-terminus to an intein-N) as described herein. rAAV particles comprising a second nucleic acid molecule (e.g. encoding an intein-C fused to the N-terminus of a C-terminal portion of the Cas9 protein or nucleobase editor) as described herein are also provided. In some embodiments, the N-terminal portion of the Cas9 protein and the C-terminal portion of the Cas9 protein are joined together to form the Cas9 protein. The disclosed rAAV particles may comprise both a first nucleic acid molecule and second nucleic acid molecules as described herein.
In another aspect, host cells comprising the compositions described herein are provided. The disclosed cells may comprise any of the disclosed nucleic acid molecules, rAAV vectors, or rAAV particles described herein.
Some aspects of the present disclosure provide compositions comprising: (i) a first nucleotide sequence encoding a N-terminal portion of a nucleobase editor fused at its C-terminus to an intein-N; and (ii) a second nucleotide sequence encoding an intein-C fused to the N-terminus of a C-terminal portion of the nucleobase editor. Further provided herein are kits comprising the any of the compositions described herein.
In some embodiments, any of the nucleobase editors of the disclosure comprises a cytosine deaminase fused to the N-terminus of a catalytically inactive Cas9 or a Cas9 nickase. In some embodiments, the cytosine deaminase is selected from the group consisting of: APOBEC1, APOBEC3, AID, and pmCDA1. In some embodiments, the nucleobase editor further comprises a uracil glycosylase inhibitor (UGI).
Still other aspects of the present disclosure provide methods comprising contacting a cell with any of the compositions described herein, wherein the contacting results in the delivery of the first nucleotide sequence and the second nucleotide sequence into the cell, and wherein the N-terminal portion of the nucleobase editor and the C-terminal portion of the nucleobase editor are joined to form a nucleobase editor.
Still other aspects of the present disclosure provide methods comprising administering to a subject in need there of a therapeutically effective amount of any of the compositions described herein. In some embodiments, the subject has a disease or disorder (e.g. a genetic disease). In particular embodiments, the disease or condition is Niemann-Pick disease type C (NPC) disease. In other embodiments, the disease or condition is congenital deafness. In some embodiments, the disease or disorder is selected from the group consisting of: cystic fibrosis, phenylketonuria, epidermolytic hyperkeratosis (EHK), chronic obstructive pulmonary disease (COPD), Charcot-Marie-Toot disease type 4J, neuroblastoma (NB), von Willebrand disease (vWD), myotonia congenital, hereditary renal amyloidosis, dilated cardiomyopathy, hereditary lymphedema, familial Alzheimer's disease, prion disease, chronic infantile neurologic cutaneous articular syndrome (CINCA), and desmin-related myopathy (DRM).
The details of certain embodiments of the invention are set forth in the Detailed Description of Certain Embodiments, as described below. Other features, objects, and advantages of the invention will be apparent from the Definitions, Examples, Figures, and Claims.
The accompanying drawings, which constitute a part of this Application, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention.
As used herein and in the claims, the singular forms “a,” “an,” and “the” include the singular and the plural reference unless the context clearly indicates otherwise. Thus, for example, a reference to “an agent” includes a single agent and a plurality of such agents.
An “adeno-associated virus” or “AAV” is a virus which infects humans and some other primate species. The wild-type AAV genome is a single-stranded deoxyribonucleic acid (ssDNA), either positive- or negative-sensed. The genome comprises two inverted terminal repeats (ITRs), one at each end of the DNA strand, and two open reading frames (ORFs): rep and cap between the ITRs. The rep ORF comprises four overlapping genes encoding Rep proteins required for the AAV life cycle. The cap ORF comprises overlapping genes encoding capsid proteins: VP1, VP2 and VP3, which interact together to form the viral capsid. VP1, VP2 and VP3 are translated from one mRNA transcript, which can be spliced in two different manners: either a longer or shorter intron can be excised resulting in the formation of two isoforms of mRNAs: a ˜2.3 kb- and a ˜2.6 kb-long mRNA isoform. The capsid forms a supramolecular assembly of approximately 60 individual capsid protein subunits into a non-enveloped, T-1 icosahedral lattice capable of protecting the AAV genome. The mature capsid is composed of VP1, VP2, and VP3 (molecular masses of approximately 87, 73, and 62 kDa respectively) in a ratio of about 1:1:10.
rAAV particles may comprise a nucleic acid vector (e.g., a recombinant genome), which may comprise at a minimum: (a) one or more heterologous nucleic acid regions comprising a sequence encoding a protein or polypeptide of interest (e.g., a split Cas9 or split nucleobase) or an RNA of interest (e.g., a gRNA), or one or more nucleic acid regions comprising a sequence encoding a Rep protein; and (b) one or more regions comprising inverted terminal repeat (ITR) sequences (e.g., wild-type ITR sequences or engineered ITR sequences) flanking the one or more nucleic acid regions (e.g., heterologous nucleic acid regions). In some embodiments, the nucleic acid vector is between 4 kb and 5 kb in size (e.g., 4.2 to 4.7 kb in size). In some embodiments, the nucleic acid vector further comprises a region encoding a Rep protein. In some embodiments, the nucleic acid vector is circular. In some embodiments, the nucleic acid vector is single-stranded. In some embodiments, the nucleic acid vector is double-stranded. In some embodiments, a double-stranded nucleic acid vector may be, for example, a self-complimentary vector that contains a region of the nucleic acid vector that is complementary to another region of the nucleic acid vector, initiating the formation of the double-strandedness of the nucleic acid vector.
As used herein, the term “adenosine deaminase” or “adenosine deaminase domain” refers to a protein or enzyme that catalyzes a deamination reaction of an adenosine (or adenine). The terms are used interchangeably. In certain embodiments, the disclosure provides nucleobase editor fusion proteins comprising one or more adenosine deaminase domains. For instance, an adenosine deaminase domain may comprise a heterodimer of a first adenosine deaminase and a second deaminase domain, connected by a linker. Adenosine deaminases (e.g., engineered adenosine deaminases or evolved adenosine deaminases) provided herein may be enzymes that convert adenine (A) to inosine (I) in DNA or RNA. Such adenosine deaminase can lead to an A:T to G:C base pair conversion. In some embodiments, the deaminase is a variant of a naturally-occurring deaminase from an organism. In some embodiments, the deaminase does not occur in nature. For example, in some embodiments, the deaminase is at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75% at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to a naturally-occurring deaminase.
In some embodiments, the adenosine deaminase is derived from a bacterium, such as, E. coli, S. aureus, S. typhi, S. putrefaciens, H. influenzae, or C. crescentus. In some embodiments, the adenosine deaminase is a TadA deaminase. In some embodiments, the TadA deaminase is an E. coli TadA deaminase (ecTadA). In some embodiments, the TadA deaminase is a truncated E. coli TadA deaminase. For example, the truncated ecTadA may be missing one or more N-terminal amino acids relative to a full-length ecTadA. In some embodiments, the truncated ecTadA may be missing 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 6, 17, 18, 19, or 20 N-terminal amino acid residues relative to the full length ecTadA. In some embodiments, the truncated ecTadA may be missing 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 6, 17, 18, 19, or 20 C-terminal amino acid residues relative to the full length ecTadA. In some embodiments, the ecTadA deaminase does not comprise an N-terminal methionine. Reference is made to U.S. Patent Publication No. 2018/0073012, published Mar. 15, 2018, which is incorporated herein by reference.
In genetics, the “antisense” strand of a segment within double-stranded DNA is the template strand, and which is considered to run in the 3′ to 5′ orientation. By contrast, the “sense” strand is the segment within double-stranded DNA that runs from 5′ to 3′, and which is complementary to the antisense strand of DNA, or template strand, which runs from 3′ to 5′. In the case of a DNA segment that encodes a protein, the sense strand is the strand of DNA that has the same sequence as the mRNA, which takes the antisense strand as its template during transcription, and eventually undergoes (typically, not always) translation into a protein. The antisense strand is thus responsible for the RNA that is later translated to protein, while the sense strand possesses a nearly identical makeup to that of the mRNA. Note that for each segment of dsDNA, there will possibly be two sets of sense and antisense, depending on which direction one reads (since sense and antisense is relative to perspective). It is ultimately the gene product, or mRNA, that dictates which strand of one segment of dsDNA is referred to as sense or antisense.
“Base editing” refers to genome editing technology that involves the conversion of a specific nucleic acid base into another at a targeted genomic locus. In certain embodiments, this can be achieved without requiring double-stranded DNA breaks (DSB), or single stranded breaks (i.e., nicking). To date, other genome editing techniques, including CRISPR-based systems, begin with the introduction of a DSB at a locus of interest. Subsequently, cellular DNA repair enzymes mend the break, commonly resulting in random insertions or deletions (indels) of bases at the site of the DSB. However, when the introduction or correction of a point mutation at a target locus is desired rather than stochastic disruption of the entire gene, these genome editing techniques are unsuitable, as correction rates are low (e.g. typically 0.1% to 5%), with the major genome editing products being indels. In order to increase the efficiency of gene correction without simultaneously introducing random indels, the present inventors previously modified the CRISPR/Cas9 system to directly convert one DNA base into another without DSB formation. See, Komor, A. C., et al., Programmable editing of a target base in genomic DNA without double-stranded DNA cleavage. Nature 533, 420-424 (2016), the entire contents of which is incorporated by reference herein.
The terms “base editor (BE)” and “nucleobase editor,” which are used interchangeably herein, refer to an agent comprising a polypeptide that is capable of making a modification to a base (e.g., A, T, C, G, or U) within a nucleic acid sequence (e.g., DNA or RNA) that converts one base to another (e.g., A to G, A to C, A to T, C to T, C to G, C to A, G to A, G to C, G to T, T to A, T to C, T to G). In some embodiments, the nucleobase editor is capable of deaminating a base within a nucleic acid such as a base within a DNA molecule. In the case of an adenine nucleobase editor, the nucleobase editor is capable of deaminating an adenine (A) in DNA. Such nucleobase editors may include a nucleic acid programmable DNA binding protein (napDNAbp) fused to an adenosine deaminase. Some nucleobase editors include CRISPR-mediated fusion proteins that are utilized in the base editing methods described herein. In some embodiments, the nucleobase editor comprises a nuclease-inactive Cas9 (dCas9) fused to a deaminase which binds a nucleic acid in a guide RNA-programmed manner via the formation of an R-loop, but does not cleave the nucleic acid. For example, the dCas9 domain of the fusion protein may include a D10A and a H840A mutation (which renders Cas9 capable of cleaving only one strand of a nucleic acid duplex), as described in PCT/US2016/058344, which published as WO 2017/070632 on Apr. 27, 2017 and is incorporated herein by reference in its entirety. The DNA cleavage domain of S. pyogenes Cas9 includes two subdomains, the HNH nuclease subdomain and the RuvC1 subdomain. The HNH subdomain cleaves the strand complementary to the gRNA (the “targeted strand”, or the strand in which editing or deamination occurs), whereas the RuvC1 subdomain cleaves the non-complementary strand containing the PAM sequence (the “non-edited strand”). The RuvC1 mutant D10A generates a nick in the targeted strand, while the HNH mutant H840A generates a nick on the non-edited strand (see Jinek et al., Science, 337:816-821(2012); Qi et al.,Cell. 28; 152(5):1173-83 (2013)).
In some embodiments, a nucleobase editor is a macromolecule or macromolecular complex that results primarily (e.g., more than 80%, more than 85%, more than 90%, more than 95%, more than 99%, more than 99.9%, or 100%) in the conversion of a nucleobase in a polynucleic acid sequence into another nucleobase (i.e., a transition or transversion) using a combination of 1) a nucleotide-, nucleoside-, or nucleobase-modifying enzyme and 2) a nucleic acid binding protein that can be programmed to bind to a specific nucleic acid sequence.
In some embodiments, the nucleobase editor comprises a DNA binding domain (e.g., a programmable DNA binding domain such as a dCas9 or nCas9) that directs it to a target sequence. In some embodiments, the nucleobase editor comprises a nucleobase modification domain fused to a programmable DNA binding domain (e.g., a dCas9 or nCas9). The terms “nucleobase modifying enzyme” and “nucleobase modification domain,” which are used interchangeably herein, refer to an enzyme that can modify a nucleobase and convert one nucleobase to another (e.g., a deaminase such as a cytidine deaminase or a adenosine deaminase). The nucleobase modifying enzyme of the the nucleobase editor may target cytosine (C) bases in a nucleic acid sequence and convert the C to thymine (T) base. In some embodiments, C to T editing is carried out by a deaminase, e.g., a cytidine deaminase. In some embodiments, A to G editing is carried out by a deaminase, e.g., an adenosine deaminase. Nucleobase editors that can carry out other types of base conversions (e.g., C to G) are also contemplated.
A “split nucleobase editor” refers to a nucleobase editor that is provided as an N-terminal portion (also referred to as a N-terminal half) and a C-terminal portion (also referred to as a C-terminal half) encoded by two separate nucleic acids. The polypeptides corresponding to the N-terminal portion and the C-terminal portion of the nucleobase editor may be combined to form a complete nucleobase editor. In some embodiments, for a nucleobase editor that comprises a dCas9 or nCas9, the “split” is located in the dCas9 or nCas9 domain, at positions as described herein in the split Cas9. Accordingly, in some embodiments, the N-terminal portion of the nucleobase editor contains the N-terminal portion of the split Cas9, and the C-terminal portion of the nucleobase editor contains the C-terminal portion of the split Cas9. Similarly, intein-N or intein-C may be fused to the N-terminal portion or the C-terminal portion of the nucleobase editor, respectively, for the joining of the N- and C-terminal portions of the nucleobase editor to form a complete nucleobase editor.
In some embodiments, a nucleobase editor converts a C to a T. In some embodiments, the nucleobase editor comprises a cytosine deaminase. A “cytosine deaminase”, or “cytidine deaminase,” refers to an enzyme that catalyzes the chemical reaction “cytosine+H2O→uracil+NH3” or “5-methyl-cytosine+H2O→thymine+NH3.” As it may be apparent from the reaction formula, such chemical reactions result in a C to U/T nucleobase change. In the context of a gene, such a nucleotide change, or mutation, may in turn lead to an amino acid change in the protein, which may affect the protein's function, e.g., loss-of-function or gain-of-function. In some embodiments, the C to T nucleobase editor comprises a dCas9 or nCas9 fused to a cytidine deaminase. In some embodiments, the cytidine deaminase domain is fused to the N-terminus of the dCas9 or nCas9. In some embodiments, the nucleobase editor further comprises a domain that inhibits uracil glycosylase, and/or a nuclear localization signal. Such nucleobase editors have been described in the art, e.g., in Rees & Liu, Nat Rev Genet. 2018; 19(12):770-788 and Koblan et al., Nat Biotechnol. 2018; 36(9):843-846; as well as U.S. Patent Publication No. 2018/0073012, published Mar. 15, 2018, which issued as U.S. Pat. No. 10,113,163; on Oct. 30, 2018; U.S. Patent Publication No. 2017/0121693, published May 4, 2017, which issued as U.S. Pat. No. 10,167,457 on Jan. 1, 2019; PCT Publication No. WO 2017/070633, published Apr. 27, 2017; U.S. Patent Publication No. 2015/0166980, published Jun. 18, 2015; U.S. Pat. No. 9,840,699, issued Dec. 12, 2017; U.S. Pat. No. 10,077,453, issued Sep. 18, 2018; PCT Publication No. WO 2019/023680, published Jan. 31, 2019; PCT Publication No. WO 2018/0176009, published Sep. 27, 2018, PCT Application No PCT/US2019/033848, filed May 23, 2019, PCT Application No. PCT/US2019/47996, filed Aug. 23, 2019; PCT Application No. PCT/US2019/049793, filed Sep. 5, 2019; International Patent Application No. PCT/US2020/028568, filed Apr. 17, 2020; PCT Application No. PCT/US2019/61685, filed Nov. 15, 2019; PCT Application No. PCT/US2019/57956, filed Oct. 24, 2019; PCT Publication No. PCT/US2019/58678, filed Oct. 29, 2019, the contents of each of which are incorporated herein by reference in their entireties.
In some embodiments, a nucleobase editor converts an A to a G. In some embodiments, the nucleobase editor comprises an adenosine deaminase. An “adenosine deaminase” is an enzyme involved in purine metabolism. It is needed for the breakdown of adenosine from food and for the turnover of nucleic acids in tissues. Its primary function in humans is the development and maintenance of the immune system. An adenosine deaminase catalyzes hydrolytic deamination of adenosine (forming inosine, which base pairs as G) in the context of DNA. There are no known natural adenosine deaminases that act on DNA. Instead, known adenosine deaminase enzymes only act on RNA (tRNA or mRNA). Evolved deoxyadenosine deaminase enzymes that accept DNA substrates and deaminate dA to deoxyinosine have been described, e.g., in PCT Application PCT/US2017/045381, filed Aug. 3, 2017, which published as WO 2018/027078, PCT Application No. PCT/US2019/033848, which published as WO 2019/226953, PCT Application No PCT/US2019/033848, filed May 23, 2019, and PCT Patent Application No. PCT/US2020/028568, filed Apr. 17, 2020; each of which is herein incorporated by reference by reference.
Exemplary adenosine and cytidine nucleobase editors are also described in Rees & Liu, Base editing: precision chemistry on the genome and transcriptome of living cells, Nat. Rev. Genet. 2018; 19(12):770-788; as well as U.S. Patent Publication No. 2018/0073012, published Mar. 15, 2018, which issued as U.S. Pat. No. 10,113,163, on Oct. 30, 2018; U.S. Patent Publication No. 2017/0121693, published May 4, 2017, which issued as U.S. Pat. No. 10,167,457 on Jan. 1, 2019; PCT Publication No. WO 2017/070633, published Apr. 27, 2017; U.S. Patent Publication No. 2015/0166980, published Jun. 18, 2015; U.S. Pat. No. 9,840,699, issued Dec. 12, 2017; and U.S. Pat. No. 10,077,453, issued Sep. 18, 2018, the contents of each of which are incorporated herein by reference in their entireties.
The term “Cas9” or “Cas9 nuclease” refers to an RNA-guided nuclease comprising a Cas9 domain, or a fragment thereof (e.g., a protein comprising an active or inactive DNA cleavage domain of Cas9, and/or the gRNA binding domain of Cas9). A “Cas9 domain” as used herein, is a protein fragment comprising an active or inactive cleavage domain of Cas9 and/or the gRNA binding domain of Cas9. A “Cas9 protein” is a full length Cas9 protein. A Cas9 nuclease is also referred to sometimes as a casnl nuclease or a CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat)-associated nuclease. CRISPR is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements, and conjugative plasmids). CRISPR clusters contain spacers, sequences complementary to antecedent mobile elements, and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). In type II CRISPR systems correct processing of pre-crRNA requires a trans-encoded small RNA (tracrRNA), endogenous ribonuclease 3 (rnc) and a Cas9 domain. The tracrRNA serves as a guide for ribonuclease 3-aided processing of pre-crRNA. Subsequently, Cas9/crRNA/tracrRNA endonucleolytically cleaves linear or circular dsDNA target complementary to the spacer. The target strand not complementary to crRNA is first cut endonucleolytically, then trimmed 3′-5′ exonucleolytically. In nature, DNA-binding and cleavage typically requires protein and both RNAs. However, single guide RNAs (“sgRNA”, or simply “gNRA”) can be engineered so as to incorporate aspects of both the crRNA and tracrRNA into a single RNA species. See, e.g., Jinek M., Chylinski K., Fonfara I., Hauer M., Doudna J. A., Charpentier E. Science 337:816-821(2012), the entire contents of which are hereby incorporated by reference. Cas9 recognizes a short motif in the CRISPR repeat sequences (the PAM or protospacer adjacent motif) to help distinguish self versus non-self. Cas9 nuclease sequences and structures are well known to those of skill in the art (see, e.g., “Complete genome sequence of an M1 strain of Streptococcus pyogenes.” Ferretti et al., J. J., McShan W. M., Ajdic D. J., Savic D. J., Savic G., Lyon K., Primeaux C., Sezate S., Suvorov A. N., Kenton S., Lai H. S., Lin S. P., Qian Y., Jia H. G., Najar F. Z., Ren Q., Zhu H., Song L., White J., Yuan X., Clifton S.W., Roe B. A., McLaughlin R. E., Proc. Natl. Acad. Sci. U.S.A. 98:4658-4663(2001); “CRISPR RNA maturation by trans-encoded small RNA and host factor RNase III.” Deltcheva E., Chylinski K., Sharma C. M., Gonzales K., Chao Y., Pirzada Z. A., Eckert M.R., Vogel J., Charpentier E., Nature 471:602-607(2011); and “A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity.” Jinek M., Chylinski K., Fonfara I., Hauer M., Doudna J. A., Charpentier E. Science 337:816-821(2012), the entire contents of each of which are incorporated herein by reference). Cas9 orthologs have been described in various species, including, but not limited to, S. pyogenes and S. thermophilus. Additional suitable Cas9 nucleases and sequences will be apparent to those of skill in the art based on this disclosure, and such Cas9 nucleases and sequences include Cas9 sequences from the organisms and loci disclosed in Chylinski, Rhun, and Charpentier, “The tracrRNA and Cas9 families of type II CRISPR-Cas immunity systems” (2013) RNA Biology 10:5, 726-737; the entire contents of which are incorporated herein by reference. In some embodiments, a Cas9 nuclease comprises one or more mutations that partially impair or inactivate the DNA cleavage domain.
A “split Cas9 protein” or “split Cas9” refers to a Cas9 protein that is provided as an N-terminal portion (which is referred to herein interchangeably as an N-terminal half) and a C-terminal portion (which is referred to herein interchangeably as a C-terminal half) encoded by two separate nucleotide sequences. The polypeptides corresponding to the N-terminal portion and the C-terminal portion of the Cas9 protein may be combined (joined) to form a complete Cas9 protein. A Cas9 protein is known to consist of a bi-lobed structure linked by a disordered linker (e.g., as described in Nishimasu et al., Cell, Volume 156, Issue 5, pp. 935-949, 2014, incorporated herein by reference). In some embodiments, the “split” occurs between the two lobes, generating two portions of a Cas9 protein, each containing one lobe.
A nuclease-inactivated Cas9 domain may interchangeably be referred to as a “dCas9” protein (for nuclease-“dead” Cas9). Methods for generating a Cas9 domain (or a fragment thereof) having an inactive DNA cleavage domain are known (see, e.g., Jinek et al., Science. 337:816-821(2012); Qi et al., “Repurposing CRISPR as an RNA-Guided Platform for Sequence-Specific Control of Gene Expression” (2013) Cell. 28; 152(5):1173-83, the entire contents of each of which are incorporated herein by reference). For example, the DNA cleavage domain of Cas9 is known to include two subdomains, the HNH nuclease subdomain and the RuvC1 subdomain. The HNH subdomain cleaves the strand complementary to the gRNA, whereas the RuvC1 subdomain cleaves the non-complementary strand. Mutations within these subdomains can silence the nuclease activity of Cas9. For example, the mutations D10A and H840A completely inactivate the nuclease activity of S. pyogenes Cas9 (Jinek et al., Science. 337:816-821(2012); Qi et al., Cell. 28; 152(5):1173-83 (2013)). In some embodiments, proteins comprising fragments of Cas9 are provided. For example, in some embodiments, a protein comprises one of two Cas9 domains: (1) the gRNA binding domain of Cas9; or (2) the DNA cleavage domain of Cas9. In some embodiments, proteins comprising Cas9 or fragments thereof are referred to as “Cas9 variants.” A Cas9 variant shares homology to Cas9, or a fragment thereof. For example, a Cas9 variant is at least about 70% identical, at least about 80% identical, at least about 90% identical, at least about 95% identical, at least about 96% identical, at least about 97% identical, at least about 98% identical, at least about 99% identical, at least about 99.5% identical, at least about 99.8% identical, or at least about 99.9% identical to wild type Cas9 (e.g., SpCas9 of SEQ ID NO: 1). In some embodiments, the Cas9 variant may have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 21, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, or more amino acid changes compared to wild type Cas9 (e.g., SpCas9 of SEQ ID NO: 1). In some embodiments, the Cas9 variant comprises a fragment of Cas9 (e.g., a gRNA binding domain or a DNA-cleavage domain), such that the fragment is at least about 70% identical, at least about 80% identical, at least about 90% identical, at least about 95% identical, at least about 96% identical, at least about 97% identical, at least about 98% identical, at least about 99% identical, at least about 99.5% identical, or at least about 99.9% identical to the corresponding fragment of wild type Cas9 (e.g., SpCas9 of SEQ ID NO: 1). In some embodiments, the fragment is at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95% identical, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% of the amino acid length of a corresponding wild type Cas9 (e.g., SpCas9 of SEQ ID NO: 1).
As used herein, the term “nCas9” or “Cas9 nickase” refers to a Cas9 or a variant thereof, which cleaves or nicks only one of the strands of a target cut site thereby introducing a nick in a double strand DNA molecule rather than creating a double strand break. This can be achieved by introducing appropriate mutations in a wild-type Cas9 which inactivates one of the two endonuclease activities of the Cas9. Any suitable mutation which inactivates one Cas9 endonuclease activity but leaves the other intact is contemplated, such as one of D10A or H840A mutations in the wild-type S. pyogenes Cas9 amino acid sequence, or a D10A mutation in the wild-type S. aureus Cas9 amino acid sequence, may be used to form the nCas9.
The term “cDNA” refers to a strand of DNA copied from an RNA template. cDNA is complementary to the RNA template.
As used herein, the term “circular permutant” refers to a protein or polypeptide (e.g., a Cas9) comprising a circular permutation, which is change in the protein's structural configuration involving a change in order of amino acids appearing in the protein's amino acid sequence. In other words, circular permutants are proteins that have altered N- and C-termini as compared to a wild-type counterpart, e.g., the wild-type C-terminal half of a protein becomes the new N-terminal half. Circular permutation (or CP) is essentially the topological rearrangement of a protein's primary sequence, connecting its N- and C-terminus, often with a peptide linker, while concurrently splitting its sequence at a different position to create new, adjacent N- and C-termini. The result is a protein structure with different connectivity, but which often can have the same overall similar three-dimensional (3D) shape, and possibly include improved or altered characteristics, including, reduced proteolytic susceptibility, improved catalytic activity, altered substrate or ligand binding, and/or improved thermostability. Circular permutant proteins can occur in nature (e.g., concanavalin A and lectin). In addition, circular permutation can occur as a result of posttranslational modifications or may be engineered using recombinant techniques. Such circularly permuted proteins (“CP-napDNAbp”, such as “CP-Cas9” in the case of Cas9), or variants thereof, retain the ability to bind DNA when complexed with a guide RNA (gRNA). See, Oakes et al., “Protein Engineering of Cas9 for enhanced function,” Methods Enzymol, 2014, 546: 491-511 and Oakes et al., “CRISPR-Cas9 Circular Permutants as Programmable Scaffolds for Genome Modification,” Cell, Jan. 10, 2019, 176: 254-267, each of are incorporated herein by reference.
The term “circularly permuted Cas9” refers to a Cas9 protein, or variant thereof (e.g., SpCas9), that occurs as or engineered as a circular permutant, whereby its N- and C-termini have been topically rearranged. The instant disclosure contemplates any previously known CP-Cas9 or use a new CP-Cas9 so long as the resulting circularly permuted protein retains the ability to bind DNA when complexed with a guide RNA (gRNA).
As used herein, a “cytosine deaminase” encoded by the CDA gene is an enzyme that catalyzes the removal of an amine group from cytidine (i.e., the base cytosine when attached to a ribose ring) to uridine (C to U) and deoxycytidine to deoxyuridine (C to U). A non-limiting example of a cytosine deaminase is APOBEC1 (“apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1”). Another example is AID (“activation-induced cytosine deaminase”). Under standard Watson-Crick hydrogen bond pairing, a cytosine base hydrogen bonds to a guanine base. When cytidine is converted to uridine (or deoxycytidine is converted to deoxyuridine), the uridine (or the uracil base of uridine) undergoes hydrogen bond pairing with the base adenine. Thus, a conversion of “C” to uridine (“U”) by cytosine deaminase will cause the insertion of “A” instead of a “G” during cellular repair and/or replication processes. Since the adenine “A” pairs with thymine “T”, the cytosine deaminase in coordination with DNA replication causes the conversion of an C.G pairing to a T.A pairing in the double-stranded DNA molecule.
“CRISPR” is a family of DNA sequences (i.e., CRISPR clusters) in bacteria and archaea that represent snippets of prior infections by a virus that have invaded the prokaryote. The snippets of DNA are used by the prokaryotic cell to detect and destroy DNA from subsequent attacks by similar viruses and effectively compose, along with an array of CRISPR-associated proteins (including Cas9 and homologs thereof) and CRISPR-associated RNA, a prokaryotic immune defense system. In nature, CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). In certain types of CRISPR systems (e.g., type II CRISPR systems), correct processing of pre-crRNA requires a trans-encoded small RNA (tracrRNA), endogenous ribonuclease 3 (rnc) and a Cas9 protein. The tracrRNA serves as a guide for ribonuclease 3-aided processing of pre-crRNA. Subsequently, Cas9/crRNA/tracrRNA endonucleolytically cleaves linear or circular dsDNA target complementary to the RNA. Specifically, the target strand not complementary to crRNA is first cut endonucleolytically, then trimmed 3′-5′ exonucleolytically. In nature, DNA-binding and cleavage typically requires protein and both RNAs. However, single guide RNAs (“sgRNA”, or simply “gRNA”) can be engineered so as to incorporate aspects of both the crRNA and tracrRNA into a single RNA species—the guide RNA. See, e.g., Jinek M., Chylinski K., Fonfara I., Hauer M., Doudna J. A., Charpentier E. Science 337:816-821(2012), the entire contents of which is hereby incorporated by reference. Cas9 recognizes a short motif in the CRISPR repeat sequences (the PAM or protospacer adjacent motif) to help distinguish self versus non-self. CRISPR biology, as well as Cas9 nuclease sequences and structures are well known to those of skill in the art (see, e.g., “Complete genome sequence of an M1 strain of Streptococcus pyogenes.” Ferretti et al., J. J., McShan W. M., Ajdic D. J., Savic D. J., Savic G., Lyon K., Primeaux C., Sezate S., Suvorov A. N., Kenton S., Lai H. S., Lin S. P., Qian Y., Jia H. G., Najar F. Z., Ren Q., Zhu H., Song L., White J., Yuan X., Clifton S.W., Roe B. A., McLaughlin R. E., Proc. Natl. Acad. Sci. U.S.A. 98:4658-4663(2001); “CRISPR RNA maturation by trans-encoded small RNA and host factor RNase III.” Deltcheva E., Chylinski K., Sharma C. M., Gonzales K., Chao Y., Pirzada Z. A., Eckert M. R., Vogel J., Charpentier E., Nature 471:602-607(2011); and “A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity.” Jinek M., Chylinski K., Fonfara I., Hauer M., Doudna J. A., Charpentier E. Science 337:816-821(2012), the entire contents of each of which are incorporated herein by reference). Cas9 orthologs have been described in various species, including, but not limited to, S. pyogenes and S. thermophilus. Additional suitable Cas9 nucleases and sequences will be apparent to those of skill in the art based on this disclosure, and such Cas9 nucleases and sequences include Cas9 sequences from the organisms and loci disclosed in Chylinski, Rhun, and Charpentier, “The tracrRNA and Cas9 families of type II CRISPR-Cas immunity systems” (2013) RNA Biology 10:5, 726-737; the entire contents of which are incorporated herein by reference.
The term “deaminase” or “deaminase domain” refers to a protein or enzyme that catalyzes a deamination reaction. In some embodiments, the deaminase is an adenosine (or adenine) deaminase, which catalyzes the hydrolytic deamination of adenine or adenosine. In some embodiments, the adenosine deaminase catalyzes the hydrolytic deamination of adenine or adenosine in deoxyribonucleic acid (DNA) to inosine. In other embodiments, the deminase is a cytidine (or cytosine) deaminase, which catalyzes the hydrolytic deamination of cytidine or cytosine.
The deaminases provided herein may be from any organism, such as a bacterium. In some embodiments, the deaminase or deaminase domain is a variant of a naturally-occurring deaminase from an organism. In some embodiments, the deaminase or deaminase domain does not occur in nature. For example, in some embodiments, the deaminase or deaminase domain is at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75% at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to a naturally-occurring deaminase.
As used herein, the term “DNA binding protein” or “DNA binding protein domain” refers to any protein that localizes to and binds a specific target DNA nucleotide sequence (e.g. a gene locus of a genome). This term embraces RNA-programmable proteins, which associate (e.g. form a complex) with one or more nucleic acid molecules (i.e., which includes, for example, guide RNA in the case of Cas systems) that direct or otherwise program the protein to localize to a specific target nucleotide sequence (e.g., DNA sequence) that is complementary to the one or more nucleic acid molecules (or a portion or region thereof) associated with the protein. Exemplary RNA-programmable proteins are CRISPR-Cas9 proteins, as well as Cas9 equivalents, homologs, orthologs, or paralogs, whether naturally occurring or non-naturally occurring (e.g. engineered or modified), and may include a Cas9 equivalent from any type of CRISPR system (e.g. type II, V, VI), including Cpf1 (a type-V CRISPR-Cas systems) (now known as Cas12a), C2c1 (a type V CRISPR-Cas system), C2c2 (a type VI CRISPR-Cas system), C2c3 (a type V CRISPR-Cas system), dCas9, GeoCas9, CjCas9, Cas12b, Cas12c, Cas12d, Cas12g, Cas12h, Cas12i, Cas13d, Cas14, Argonaute, and nCas9. Further Cas-equivalents are described in Makarova et al., “C2c2 is a single-component programmable RNA-guided RNA-targeting CRISPR effector,” Science 2016; 353(6299), the contents of which are incorporated herein by reference.
The term “DNA editing efficiency,” as used herein, refers to the number or proportion of intended base pairs that are edited. For example, if a nucleobase editor edits 10% of the base pairs that it is intended to target (e.g., within a cell or within a population of cells), then the nucleobase editor can be described as being 10% efficient. Some aspects of editing efficiency embrace the modification (e.g. deamination) of a specific nucleotide within DNA, without generating a large number or percentage of insertions or deletions (i.e., indels). It is generally accepted that editing while generating less than 5% indels (as measured over total target nucleotide substrates) is high editing efficiency. The generation of more than 20% indels is generally accepted as poor or low editing efficiency. Indel formation may be measured by techniques known in the art, including high-throughput screening of sequencing reads.
The term “off-target editing frequency,” as used herein, refers to the number or proportion of unintended base pairs, e.g. DNA base pairs, that are edited. On-target and off-target editing frequencies may be measured by the methods and assays described herein, further in view of techniques known in the art, including high-throughput sequencing reads. As used herein, high-throughput sequencing involves the hybridization of nucleic acid primers (e.g., DNA primers) with complementarity to nucleic acid (e.g., DNA) regions just upstream or downstream of the target sequence or off-target sequence of interest. Because the DNA target sequence and the Cas9-independent off-target sequences are known a priori in the methods disclosed herein, nucleic acid primers with sufficient complementarity to regions upstream or downstream of the target sequence and Cas9-independent off-target sequences of interest may be designed using techniques known in the art, such as the PhusionU PCR kit (Life Technologies), Phusion HS II kit (Life Technologies), and Illumina MiSeq kit. Since many of the Cas9-dependent off-target sites have high sequence identity to the target site of interest, nucleic acid primers with sufficient complementarity to regions upstream or downstream of the Cas9-dependent off-target site may likewise be designed using techniques and kits known in the art. These kits make use of polymerase chain reaction (PCR) amplification, which produces amplicons as intermediate products. The target and off-target sequences may comprise genomic loci that further comprise protospacers and PAMs. Accordingly, the term “amplicons,” as used herein, may refer to nucleic acid molecules that constitute the aggregates of genomic loci, protospacers and PAMs. High-throughput sequencing techniques used herein may further include Sanger sequencing and IIlumina-based next-generation genome sequencing (NGS).
The term “on-target editing,” as used herein, refers to the introduction of intended modifications (e.g., deaminations) to nucleotides (e.g., adenine) in a target sequence, such as using the nucleobase editors described herein. The term “off-target DNA editing,” as used herein, refers to the introduction of unintended modifications (e.g. deaminations) to nucleotides (e.g. adenine) in a sequence outside the canonical nucleobase editor binding window (i.e., from one protospacer position to another, typically 2 to 8 nucleotides long). Off-target DNA editing can result from weak or non-specific binding of the gRNA sequence to the target sequence.
As used herein, the terms “upstream” and “downstream” are terms of relativety that define the linear position of at least two elements located in a nucleic acid molecule (whether single or double-stranded) that is orientated in a 5′-to-3′ direction. In particular, a first element is upstream of a second element in a nucleic acid molecule where the first element is positioned somewhere that is 5′ to the second element. For example, a SNP is upstream of a Cas9-induced nick site if the SNP is on the 5′ side of the nick site. Conversely, a first element is downstream of a second element in a nucleic acid molecule where the first element is positioned somewhere that is 3′ to the second element. For example, a SNP is downstream of a Cas9-induced nick site if the SNP is on the 3′ side of the nick site. The nucleic acid molecule can be a DNA (double or single stranded). RNA (double or single stranded), or a hybrid of DNA and RNA. The analysis is the same for single strand nucleic acid molecule and a double strand molecule since the terms upstream and downstream are in reference to only a single strand of a nucleic acid molecule, except that one needs to select which strand of the double stranded molecule is being considered. Often, the strand of a double stranded DNA which can be used to determine the positional relativity of at least two elements is the “sense” or “coding” strand. In genetics, a “sense” strand is the segment within double-stranded DNA that runs from 5′ to 3′, and which is complementary to the antisense strand of DNA, or template strand, which runs from 3′ to 5′. Thus, as an example, a SNP nucleobase is “downstream” of a promoter sequence in a genomic DNA (which is double-stranded) if the SNP nucleobase is on the 3′ side of the promoter on the sense or coding strand.
The term “base edit:indel ratio,” as used herein, refers to the ratio of intended DNA nucleobase modifications (e.g., point mutations or deaminations) to formation of indels.
The term “effective amount,” as used herein, refers to an amount of a biologically active agent that is sufficient to elicit a desired biological response. For example, in some embodiments, an effective amount of a nucleobase editor may refer to the amount of the editor that is sufficient to edit a target site nucleotide sequence, e.g., a genome. In some embodiments, an effective amount of a nucleobase editor provided herein, e.g., of a fusion protein comprising a nickase Cas9 domain and a guide RNA may refer to the amount of the fusion protein that is sufficient to induce editing of a target site specifically bound and edited by the fusion protein. As will be appreciated by the skilled artisan, the effective amount of an agent, e.g., a fusion protein, a nuclease, a hybrid protein, a protein dimer, a complex of a protein (or protein dimer) and a polynucleotide, or a polynucleotide, may vary depending on various factors as, for example, on the desired biological response, e.g., on the specific allele, genome, or target site to be edited, on the cell or tissue being targeted, and on the agent being used.
The term “functional equivalent” refers to a second biomolecule that is equivalent in function, but not necessarily equivalent in structure to a first biomolecule. For example, a “Cas9 equivalent” refers to a protein that has the same or substantially the same functions as Cas9, but not necessarily the same amino acid sequence. In the context of the disclosure, the specification refers throughout to “a protein X, or a functional equivalent thereof.” In this context, a “functional equivalent” of protein X embraces any homolog, paralog, fragment, naturally occurring, engineered, circular permutant, mutated, or synthetic version of protein X which bears an equivalent function.
The term “fusion protein” as used herein refers to a hybrid polypeptide which comprises protein domains from at least two different proteins. One protein may be located at the amino-terminal (N-terminal) portion of the fusion protein or at the carboxy-terminal (C-terminal) protein thus forming an “amino-terminal fusion protein” or a “carboxy-terminal fusion protein,” respectively. A protein may comprise different domains, for example, a nucleic acid binding domain (e.g., the gRNA binding domain of Cas9 that directs the binding of the protein to a target site) and a nucleic acid cleavage domain or a catalytic domain of a nucleic-acid editing protein. Another example includes a Cas9 or equivalent thereof fused to an adenosine deaminae. Any of the proteins provided herein may be produced by any method known in the art. For example, the proteins provided herein may be produced via recombinant protein expression and purification, which is especially suited for fusion proteins comprising a peptide linker. Methods for recombinant protein expression and purification are well known, and include those described by Green and Sambrook, Molecular Cloning: A Laboratory Manual (4th ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (2012)), the entire contents of which are incorporated herein by reference.
Two proteins or protein domains are considered to be “fused” when a peptide bond is formed linking the two proteins or two protein domains. In some embodiments, a linker (e.g., a peptide linker) is present between the two proteins or two protein domains. The term “linker,” as used herein, refers to a chemical group or a molecule linking two molecules or moieties, e.g., two domains of a fusion protein, such as, for example, a nuclease-inactive Cas9 domain and a nucleic acid editing domain (e.g., a deaminase domain). Typically, the linker is positioned between, or flanked by, two groups, molecules, or other moieties and connected to each one via a covalent bond, thus connecting the two. In some embodiments, the linker is an amino acid or a plurality of amino acids (e.g., a peptide or protein). In some embodiments, the linker is an organic molecule, group, polymer, or chemical moiety. In some embodiments, the linker is 5-100 amino acids in length, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 30-35, 35-40, 40-45, 45-50, 50-60, 60-70, 70-80, 80-90, 90-100, 100-150, or 150-200 amino acids in length. Longer or shorter linke are also contemplated.
The term “guide nucleic acid” or “napDNAbp-programming nucleic acid molecule” or equivalently “guide sequence” refers the one or more nucleic acid molecules which associate with and direct or otherwise program a napDNAbp protein to localize to a specific target nucleotide sequence (e.g., a gene locus of a genome) that is complementary to the one or more nucleic acid molecules (or a portion or region thereof) associated with the protein, thereby causing the napDNAbp protein to bind to the nucleotide sequence at the specific target site. A non-limiting example is a guide RNA of a Cas protein of a CRISPR-Cas genome editing system. Chemically, guide nucleic acids can be all RNA, all DNA, or a chimeric of RNA and DNA. The guide nucleic acids may also include nucleotide analogs. Guide nucleic acids can be expressed as transcription products or can be synthesized.
As used herein, a “guide RNA” can refer to a synthetic fusion of the endogenous bacterial crRNA and tracrRNA that provides both targeting specificity and a scaffold and/or binding ability for Cas9 nuclease to a target DNA. This synthetic fusion does not exist in nature and is also commonly referred to as an sgRNA. However, the term, guide RNA, also embraces equivalent guide nucleic acid molecules that associate with Cas9 equivalents, homologs, orthologs, or paralogs, whether naturally occurring or non-naturally occurring (e.g., engineered or recombinant), and which otherwise program the Cas9 equivalent to localize to a specific target nucleotide sequence. The Cas9 equivalents may include other napDNAbps from any type of CRISPR system (e.g., type II, V, VI), including Cpf1 (a type-V CRISPR-Cas systems) (now known as Cas12a), C2c1 (a type V CRISPR-Cas system), C2c2 (a type VI CRISPR-Cas system) and C2c3 (a type V CRISPR-Cas system). Further Cas-equivalents are described in Makarova et al., “C2c2 is a single-component programmable RNA-guided RNA-targeting CRISPR effector,” Science 2016; 353(6299), the contents of which are incorporated herein by reference. Exemplary sequences are and structures of guide RNAs are provided herein. In addition, methods for designing appropriate guide RNA sequences are provided herein.
A guide RNA is a particular type of guide nucleic acid which is mostly commonly associated with a Cas protein of a CRISPR-Cas9 and which associates with Cas9, directing the Cas9 protein to a specific sequence in a DNA molecule that includes complementarity to the protospacer sequence for the guide RNA. Functionally, guide RNAs associate with Cas9, directing (or programming) the Cas9 protein to a specific sequence in a DNA molecule that includes a sequence complementary to the protospacer sequence for the guide RNA. A gRNA is a component of the CRISPR/Cas system. Typically, a guide RNA comprises a fusion of a CRISPR-targeting RNA (crRNA) and a trans-activation crRNA (tracrRNA), providing both targeting specificity and scaffolding/binding ability for Cas9 nuclease. A “crRNA” is a bacterial RNA that confers target specificity and requires tracrRNA to bind to Cas9. A “tracrRNA” is a bacterial RNA that links the crRNA to the Cas9 nuclease and typically can bind any crRNA. The sequence specificity of a Cas DNA-binding protein is determined by gRNAs, which have nucleotide base-pairing complementarity to target DNA sequences. The native gRNA comprises a 20 nucleotide (nt) Specificity Determining Sequence (SDS), or spacer, which specifies the DNA sequence to be targeted, and is immediately followed by a 80 nt scaffold sequence, which associates the gRNA with Cas9. In some embodiments, an SDS of the present disclosure has a length of 15 to 100 nucleotides, or more. For example, an SDS may have a length of 15 to 90, 15 to 85, 15 to 80, 15 to 75, 15 to 70, 15 to 65, 15 to 60, 15 to 55, 15 to 50, 15 to 45, 15 to 40, 15 to 35, 15 to 30, or 15 to 20 nucleotides. In some embodiments, the SDS is 20 nucleotides long. For example, the SDS may be 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nucleotides long. At least a portion of the target DNA sequence is complementary to the SDS of the gRNA. For Cas9 to successfully bind to the DNA target sequence, a region of the target sequence is complementary to the SDS of the gRNA sequence and is immediately followed by the correct protospacer adjacent motif (PAM) sequence (e.g., NGG for Cas9 and TTN, TTTN, or YTN for Cpf1). In some embodiments, an SDS is 100% complementary to its target sequence. In some embodiments, the SDS sequence is less than 100% complementary to its target sequence and is, thus, considered to be partially complementary to its target sequence. For example, a targeting sequence may be 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, or 90% complementary to its target sequence. In some embodiments, the SDS of template DNA or target DNA may differ from a complementary region of a gRNA by 1, 2, 3, 4 or 5 nucleotides.
In some embodiments, the guide RNA is about 15-120 nucleotides long and comprises a sequence of at least 10 contiguous nucleotides that is complementary to a target sequence. In some embodiments, the guide RNA is 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, or 120 nucleotides long. In some embodiments, the guide RNA comprises a sequence of 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more contiguous nucleotides that is complementary to a target sequence. Sequence complementarity refers to distinct interactions between adenine and thymine (DNA) or uracil (RNA), and between guanine and cytosine.
As used herein, a “spacer sequence” is the sequence of the guide RNA (˜20 nts in length) which has the same sequence (with the exception of uridine bases in place of thymine bases) as the protospacer of the PAM strand of the target (DNA) sequence, and which is complementary to the target strand (or non-PAM strand) of the target sequence.
As used herein, the “target sequence” refers to the ˜20 nucleotides in the target DNA sequence that have complementarity to the protospacer sequence in the PAM strand. The target sequence is the sequence that anneals to or is targeted by the spacer sequence of the guide RNA. The spacer sequence of the guide RNA and the protospacer have the same sequence (except the spacer sequence is RNA, and the protospacer is DNA).
As used herein, the terms “guide RNA core,” “guide RNA scaffold sequence” and “backbone sequence,” which are used interchangeably, refer to the region (or sequence) within the gRNA that is responsible for Cas9 binding. It does not include the 20 bp spacer sequence that is used to guide Cas9 to target DNA. This region also known as the crRNA/tracrRNA. The guide RNA backbone sequence is separate from the guide sequence, or spacer, region of the guide RNA, which has complementarity to a protospacer of a nucleic acid molecule.
As used herein, the term “protospacer” refers to the sequence (e.g., a ˜20 bp sequence) in DNA adjacent to the PAM (protospacer adjacent motif) sequence which shares the same sequence as the spacer sequence of the guide RNA, and which is complementary to the target sequence of the non-PAM strand. The spacer sequence of the guide RNA anneals to the target sequence located on the non-PAM strand. In order for Cas9 to function it also requires a specific protospacer adjacent motif (PAM) that varies depending on the bacterial species of the Cas9 gene. The most commonly used Cas9 nuclease, derived from S. pyogenes, recognizes a PAM sequence of NGG that is found directly downstream of the protospacer sequence in the genomic DNA, on the non-target strand. The skilled person will appreciate that the literature in the state of the art sometimes refers to the “protospacer” as the ˜20-nt target-specific guide sequence on the guide RNA itself, rather than referring to it as a “spacer” (and that the protospacer (DNA) and the spacer (RNA) have the same sequence). Thus, the term “protospacer” as used herein may be used interchangeably with the term “spacer.” The context of the discription surrounding the appearance of either “protospacer” or “spacer” will help inform the reader as to whether the term is reference to the gRNA or the DNA sequence. Both usages of these terms are acceptable since the state of the art uses both terms in each of these ways.
A “protospacer adjacent motif” (PAM) is typically a sequence of nucleotides located adjacent to (e.g., within 10, 9, 8, 7, 6, 5, 4, 3, 3, or 1 nucleotide(s) of a target sequence). A PAM sequence is “immediately adjacent to” a target sequence if the PAM sequence is contiguous with the target sequence (that is, if there are no nucleotides located between the PAM sequence and the target sequence). In some embodiments, a PAM sequence is a wild-type PAM sequence. Examples of PAM sequences include, without limitation, NGG, NGR, NNGRR(T/N), NNNNGATT, NNAGAAW, NGGAG, NAAAAC, AWG, and CC. In some embodiments, a PAM sequence is obtained from Streptococcus pyogenes (e.g., NGG or NGR). In some embodiments, a PAM sequence is obtained from Staphylococcus aureus (e.g., NNGRR(T/N)). In some embodiments, a PAM sequence is obtained from Neisseria meningitidis (e.g., NNNNGATT). In some embodiments, a PAM sequence is obtained from Streptococcus thermophilus (e.g., NNAGAAW or NGGAG). In some embodiments, a PAM sequence is obtained from Treponema denticola (e.g., NAAAAC). In some embodiments, a PAM sequence is obtained from Escherichia coli (e.g., AWG). In some embodiments, a PAM sequence is obtained from Pseudomonas auruginosa (e.g., CC). Other PAM sequences are contemplated. A PAM sequence is typically located downstream (i.e., 3′) from the target sequence, although in some embodiments a PAM sequence may be located upstream (i.e., 5′) from the target sequence.
The term “host cell,” as used herein, refers to a cell that can host, replicate, and transfer a phage vector useful for a continuous evolution process as provided herein. In embodiments where the vector is a viral vector, a suitable host cell is a cell that may be infected by the viral vector, can replicate it, and can package it into viral particles that can infect fresh host cells. A cell can host a viral vector if it supports expression of genes of viral vector, replication of the viral genome, and/or the generation of viral particles. One criterion to determine whether a cell is a suitable host cell for a given viral vector is to determine whether the cell can support the viral life cycle of a wild-type viral genome that the viral vector is derived from. For example, if the viral vector is a modified M13 phage genome, as provided in some embodiments described herein, then a suitable host cell would be any cell that can support the wild-type M13 phage life cycle. Suitable host cells for viral vectors useful in continuous evolution processes are well known to those of skill in the art, and the disclosure is not limited in this respect. In some embodiments, the viral vector is a phage and the host cell is a bacterial cell. In some embodiments, the host cell is an E. coli cell. Suitable E. coli host strains will be apparent to those of skill in the art, and include, but are not limited to, New England Biolabs (NEB) Turbo, Top10F′, DH12S, ER2738, ER2267, and XL1-Blue MRF′. These strain names are art recognized and the genotype of these strains has been well characterized. It should be understood that the above strains are exemplary only and that the invention is not limited in this respect. The term “fresh,” as used herein interchangeably with the terms “non-infected” or “uninfected” in the context of host cells, refers to a host cell that has not been infected by a viral vector comprising a gene of interest as used in a continuous evolution process provided herein. A fresh host cell can, however, have been infected by a viral vector unrelated to the vector to be evolved or by a vector of the same or a similar type but not carrying the gene of interest.
In some embodiments, the host cell is a prokaryotic cell, for example, a bacterial cell. In some embodiments, the host cell is an E. coli cell. In some embodiments, the host cell is a eukaryotic cell, for example, a yeast cell, a plant cell, an insect cell, or a mammalian cell. In some embodiments, the cell is a human cell. The type of host cell, will, of course, depend on the viral vector employed, and suitable host cell/viral vector combinations will be readily apparent to those of skill in the art.
An “intein” is a segment of a protein that is able to excise itself and join the remaining portions (the exteins) with a peptide bond in a process known as protein splicing. Inteins are also referred to as “protein introns.” The process of an intein excising itself and joining the remaining portions of the protein is herein termed “protein splicing” or “intein-mediated protein splicing.” In some embodiments, an intein of a precursor protein (an intein containing protein prior to intein-mediated protein splicing) comes from two genes. Such intein is referred to herein as a split intein. For example, in cyanobacteria, DnaE, the catalytic subunit a of DNA polymerase III, is encoded by two separate genes, dnaE-n and dnaE-c. The intein encoded by the dnaE-n gene is herein referred as “intein-N.” The intein encoded by the dnaE-c gene is herein referred as “intein-C.”
Other intein systems may also be used. For example, a synthetic intein based on the dnaE intein, the Cfa-N and Cfa-C intein pair, has been described (e.g., in Stevens et al., J Am Chem Soc. 2016 Feb. 24; 138(7):2162-5, incorporated herein by reference). As another example, a synthetic intein based on the dnaE intein, the Nostoc punctiforme (Npu) intein pair, has been described (see Zettler, J., Schutz, V. & Mootz, H. D., The naturally split Npu DnaE intein exhibits an extraordinarily high rate in the protein trans-splicing reaction. FEBS letters 583, 909-914 (2009), incorporated herein by reference). Non-limiting examples of intein pairs that may be used in accordance with the present disclosure include: Cfa DnaE intein, Npu DnaE intein, Ssp GyrB intein, Ssp DnaX intein, Ter DnaE3 intein, Ter ThyX intein, Rma DnaB intein and Cne Prp8 intein (e.g., as described in U.S. Pat. No. 8,394,604, incorporated herein by reference).
Exemplary nucleotide and amino acid sequences of inteins are provided below, as SEQ ID NOs: 350-357. In some embodiments, the inteins used in accordance with the disclosed napDNAbp domains (e.g., Cas9 domains) comprise the Npu intein-N comprising the amino acid sequence of SEQ ID NO: 351 and the the Npu intein-C comprising the amino acid sequence of SEQ ID NO: 353. In some embodiments, the inteins used in accordance with the disclosed nucleobase editors comprise the Npu intein-N comprising the amino acid sequence of SEQ ID NO: 351 and the Npu intein-C comprising the amino acid sequence of SEQ ID NO: 353. In some embodiments, the inteins used in accordance with the disclosed constructs encoding any of the disclosed napDNAbp domains (e.g., a Cas9 domain) comprise the Npu intein-N DNA comprising the nucleotide sequence of SEQ ID NO: 350 and the the Npu intein-C DNA comprising the nucleotide sequence of SEQ ID NO: 352. In some embodiments, the inteins used in accordance with the disclosed constructs encoding any of the disclosed nucleobase editors comprise the Npu intein-N DNA comprising the nucleotide sequence of SEQ ID NO: 350 and the Npu intein-C DNA comprising the nucleotide sequence of SEQ ID NO: 352.
In some embodiments, the intein-N comprises an amino acid sequence that is at least 90%, 95%, 98%, or 99% identical to the amino acid of SEQ ID NOs: 351 or 355. In some embodiments, the intein-N comprises an amino acid sequence that differs from the amino acid of SEQ ID NOs: 351 or 355 by 1, 2, 3, 4, 5, 6, or 7 amino acids. In some embodiments, the intein-N comprises the amino acid sequence of SEQ ID NOs: 351 or 355. In some embodiments, the intein-N used in accordance with the disclosed constructs comprises a nucleotide sequence that is at least 90%, 95%, 98%, or 99% identical to the nucleotide sequence of SEQ ID NOs: 350 or 354. In some embodiments, the intein-N used in accordance with the disclosed constructs comprises a nucleotide sequence that differs by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 10-15 nucleotides from the nucleotide sequence of SEQ ID NOs: 350 or 354.
In some embodiments, the intein-C comprises an amino acid sequence that is at least 90%, 95%, 98%, or 99% identical to the amino acid of SEQ ID NOs: 353 or 357. In some embodiments, the intein-C comprises an amino acid sequence that differs from the amino acid of SEQ ID NOs: 353 or 357 by 1, 2, 3, 4, or 5 amino acids. In some embodiments, the intein-C comprises the amino acid sequence of SEQ ID NOs: 351 or 355. In some embodiments, the intein-C used in accordance with the disclosed constructs comprises a nucleotide sequence that is at least 90%, 95%, 98%, or 99% identical to the nucleotide sequence of SEQ ID NOs: 352 or 356. In some embodiments, the intein-C used in accordance with the disclosed constructs comprises a nucleotide sequence that differs by 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 nucleotides from the nucleotide sequence of SEQ ID NOs: 352 or 356.
In particular embodiments, the intein-N comprises the amino acid sequence as set forth in SEQ ID NO: 355. In some embodiments, the intein-C comprises the amino acid sequence as set forth in SEQ ID NO: 357.
Intein-N and intein-C may be fused to the N-terminal portion of the split Cas9 and the C-terminal portion of the split Cas9, respectively, for the joining of the N-terminal portion of the split Cas9 and the C-terminal portion of the split Cas9. For example, in some embodiments, an intein-N is fused to the C-terminus of the N-terminal portion of the split Cas9, i.e., to form a structure of N-[N-terminal portion of the split Cas9]-[intein-N]-C. In some embodiments, an intein-C is fused to the N-terminus of the C-terminal portion of the split Cas9, i.e., to form a structure of N-[intein-C]-[C-terminal portion of the split Cas9]-C. The mechanism of intein-mediated protein splicing for joining the proteins the inteins are fused to (e.g., split Cas9) is known in the art, e.g., as described in Shah et al., Chem Sci. 2014; 5(1):446-461, incorporated herein by reference.
The term “mutation,” as used herein, refers to a substitution of a residue within a sequence, e.g. a nucleic acid or amino acid sequence, with another residue; a deletion or insertion of one or more residues within a sequence; or a substitution of a residue within a sequence of a genome in a subject to be corrected. Mutations are typically described herein by identifying the original residue followed by the position of the residue within the sequence and by the identity of the newly substituted residue. Various methods for making the amino acid substitutions (mutations) provided herein are well known in the art, and are provided by, for example, Green and Sambrook, Molecular Cloning: A Laboratory Manual (4th ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (2012)). Mutations can include a variety of categories, such as single base polymorphisms, microduplication regions, indel, and inversions, and is not meant to be limiting in any way. Mutations can include “loss-of-function” mutations which are mutations that reduce or abolish a protein activity. Most loss-of-function mutations are recessive, because in a heterozygote the second chromosome copy carries an unmutated version of the gene coding for a fully functional protein whose presence compensates for the effect of the mutation. There are some exceptions where a loss-of-function mutation is dominant, one example being haploinsufficiency, where the organism is unable to tolerate the approximately 50% reduction in protein activity suffered by the heterozygote. This is the explanation for a few genetic diseases in humans, including Marfan syndrome, which results from a mutation in the gene for the connective tissue protein called fibrillin. Mutations also embrace “gain-of-function” mutations, which is one which confers an abnormal activity on a protein or cell that is otherwise not present in a normal condition. Many gain-of-function mutations are in regulatory sequences rather than in coding regions, and can therefore have a number of consequences. Because of their nature, gain-of-function mutations are usually dominant. Many loss-of-function mutations are recessive, such as autosomal recessive.
The term “napDNAbp” which stand for “nucleic acid programmable DNA binding protein” refers to any protein that may associate (e.g., form a complex) with one or more nucleic acid molecules (i.e., which may broadly be referred to as a “napDNAbp-programming nucleic acid molecule” and includes, for example, guide RNA in the case of Cas systems) which direct or otherwise program the protein to localize to a specific target nucleotide sequence (e.g., a gene locus of a genome) that is complementary to the one or more nucleic acid molecules (or a portion or region thereof) associated with the protein, thereby causing the protein to bind to the nucleotide sequence at the specific target site. This term napDNAbp embraces CRISPR-Cas9 proteins, as well as Cas9 equivalents, homologs, orthologs, or paralogs, whether naturally occurring or non-naturally occurring (e.g., engineered or modified), and may include a Cas9 equivalent from any type of CRISPR system (e.g., type II, V, VI), including Cpf1 (a type-V CRISPR-Cas systems) (now known as Cas12a), C2c1 (a type V CRISPR-Cas system), C2c2 (a type VI CRISPR-Cas system), C2c3 (a type V CRISPR-Cas system), dCas9, GeoCas9, CjCas9, Cas12a, Cas12b, Cas12c, Cas12d, Cas12g, Cas12h, Cas12i, Cas13d, Cas14, Argonaute, and nCas9. Further Cas-equivalents are described in Makarova et al., “C2c2 is a single-component programmable RNA-guided RNA-targeting CRISPR effector,” Science 2016; 353 (6299), the contents of which are incorporated herein by reference. However, the nucleic acid programmable DNA binding protein (napDNAbp) that may be used in connection with this invention are not limited to CRISPR-Cas systems. The invention embraces any such programmable protein, such as the Argonaute protein from Natronobacterium gregoryi (NgAgo) which may also be used for DNA-guided genome editing. NgAgo-guide DNA system does not require a PAM sequence or guide RNA molecules, which means genome editing can be performed simply by the expression of generic NgAgo protein and introduction of synthetic oligonucleotides on any genomic sequence. See Gao et al., DNA-guided genome editing using the Natronobacterium gregoryi Argonaute. Nature Biotechnology 2016; 34(7):768-73, which is incorporated herein by reference.
In some embodiments, the napDNAbp is a RNA-programmable nuclease, when in a complex with an RNA, may be referred to as a nuclease:RNA complex. Typically, the bound RNA(s) is referred to as a guide RNA (gRNA). gRNAs can exist as a complex of two or more RNAs, or as a single RNA molecule. gRNAs that exist as a single RNA molecule may be referred to as single-guide RNAs (sgRNAs), though “gRNA” is used interchangeably to refer to guide RNAs that exist as either single molecules or as a complex of two or more molecules. Typically, gRNAs that exist as single RNA species comprise two domains: (1) a domain that shares homology to a target nucleic acid (e.g., and directs binding of a Cas9 (or equivalent) complex to the target); and (2) a domain that binds a Cas9 protein. In some embodiments, domain (2) corresponds to a sequence known as a tracrRNA, and comprises a stem-loop structure. For example, in some embodiments, domain (2) is homologous to a tracrRNA as depicted in
The napDNAbp nucleases (e.g., Cas9) use RNA:DNA hybridization to target DNA cleavage sites, these proteins are able to be targeted, in principle, to any sequence specified by the guide RNA. Methods of using napDNAbp nucleases, such as Cas9, for site-specific cleavage (e.g., to modify a genome) are known in the art (see e.g., Cong, L. et al. Multiplex genome engineering using CRISPR/Cas systems. Science 339, 819-823 (2013); Mali, P. et al. RNA-guided human genome engineering via Cas9. Science 339, 823-826 (2013); Hwang, W. Y. et al. Efficient genome editing in zebrafish using a CRISPR-Cas system. Nature Biotechnology 31, 227-229 (2013); Jinek, M. et al. RNA-programmed genome editing in human cells. eLife 2, e00471 (2013); Dicarlo, J. E. et al., Genome engineering in Saccharomyces cerevisiae using CRISPR-Cas systems. Nucleic Acid Res. (2013); Jiang, W. et al. RNA-guided editing of bacterial genomes using CRISPR-Cas systems. Nature Biotechnology 31, 233-239 (2013); the entire contents of each of which are incorporated herein by reference).
The term “nickase” refers to a napDNAbp (e.g., a Cas9) having only a single nuclease activity that cuts only one strand of a target DNA, rather than both strands. Thus, a nickase type napDNAbp does not leave a double-strand break. Exemplary nickases include SpCas9 and SaCas9 nickases. An exemplary nickase comprises a sequence having at least 99%, or 100%, identity to the amino acid sequence of SEQ ID NO: 3 or 11.
A “uracil glycosylase inhibitor (UGI)” refers to a protein that inhibits the activity of uracil-DNA glycosylase. Suitable UGI proteins for use in accordance with the present disclosure include, for example, those published in Wang et al., J. Biol. Chem. 264:1163-1171(1989); Lundquist et al., J. Biol. Chem. 272:21408-21419(1997); Ravishankar et al., Nucleic Acids Res. 26:4880-4887(1998); and Putnam et al., J. Mol. Biol. 287:331-346 (1999), each of which is incorporated herein by reference. Non-limiting, exemplary proteins that may be used as a UGI of the present disclosure and their respective sequences are provided below. In some embodiments, the UGI is a variant of a naturally-occurring deaminase from an organism, and the variants do not occur in nature. For example, in some embodiments, the UGI is at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75% at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to a naturally-occurring UGI from an organism or any UGIs provided herein (e.g., a UGI comprising the amino acid sequence of any one of SEQ ID NOs: 299-302). In some embodiments, the UGI comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 30%, no more than 25%, no more than 20%, no more than 15%, no more than 10%, no more than 5%, no more than 1% longer or shorter) than any of the UGIs provided herein. In some embodiments, the UGI comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 20 amino acids, no more than 15 amino acids, no more than 10 amino acids, no more than 5 amino acids, no more than 2 amino acids longer or shorter) than any of the UGIs provided herein.
A “nuclear localization signal” or “NLS” refers to as an amino acid sequence that “tags” a protein for import into the cell nucleus by nuclear transport. Typically, this signal consists of one or more short sequences of positively charged lysines or arginines exposed on the protein surface. One or more NLS may be added to the N- or C-terminus of a protein, or internally (e.g., between two protein domains). For example, one or more NLS may be added to the N- or C-terminus of a nucleobase editor, or between the Cas9 and the deaminase in a nucleobase editor. In some embodiments, 1, 2, 3, 4, 5, or more NLS may be added. Nuclear localization sequences are known in the art and would be apparent to the skilled artisan. For example, NLS sequences are described in Plank et al., PCT/EP2000/011690, filed Nov. 23, 2000, the contents of which are incorporated herein by reference for its disclosure of exemplary nuclear localization sequences. In some embodiments, a NLS comprises a bipartite nuclear localization signal comprising an amino acid sequence selected from the group consisting of KRTADGSEFEPKKKRKV (SEQ ID NO: 398), KRPAATKKAGQAKKKK (SEQ ID NO: 344), KKTELQTTNAENKTKKL (SEQ ID NO: 345), KRGINDRNFWRGENGRKTR(SEQ ID NO: 346), RKSGKIAAIVVKRPRK (SEQ ID NO: 347), PKKKRKV (SEQ ID NO: 373) or MDSLLMNRRKFLYQFKNVRWAKGRRETYLC (SEQ ID NO: 374). In some embodiments, a linker is inserted between the Cas9 and the deaminase. In certain embodiments, the NLS comprises the amino acid sequence of SEQ ID NO: 398. In some embodiments, the NLS comprises the amino acid sequence of SEQ ID NO: 344.
An NLS can be classified as monopartite or bipartite. A non-limiting example of a monopartite NLS is the sequence PKKKRKV (SEQ ID NO: 373) in the SV40 Large T-antigen. A “bipartite” NLS typically contains two clusters of basic amino acids, separated by a spacer of about 10 amino acids. One non-limiting example of a bipartite NLS is the NLS of nucleoplasmin, KRPAATKKAGQAKKKK (spacer underlined) (SEQ ID NO: 344). In some embodiments, the NLS used in accordance with the present disclosure is the NLS of nucleoplasmin comprising the amino acid sequence of KRPAATKKAGQAKKKK (SEQ ID NO: 344). Other bipartite NLSs that may be used in accordance with the present disclosure include, without limitation: SV40 bipartite NLS (KRTADGSEFESPKKKRKV (SEQ ID NO: 375), e.g., as described in Hodel et al., J Biol Chem. 2001 Jan. 12; 276(2):1317-25, incorporated herein by reference); Kanadaptin bipartite NLS (KKTELQTTNAENKTKKL (SEQ ID NO: 345), e.g., as described in Hubner et al., Biochem J. 2002 Jan. 15; 361 (Pt 2):287-96, incorporated herein by reference); influenza A nucleoprotein bipartite NLS (KRGINDRNFWRGENGRKTR (SEQ ID NO: 346), e.g., as described in Ketha et al., BMC Cell Biology. 2008; 9:22, incorporated herein by reference); and ZO-2 bipartite NLS (RKSGKIAAIVVKRPRK (SEQ ID NO: 347), e.g., as described in Quiros et al., Nusrat A, ed. Molecular Biology of the Cell. 2013; 24(16):2528-2543, incorporated herein by reference).
The nucleotide sequence encoding an NLS is “operably linked” to the nucleotide sequence encoding a protein to which the NLS is fused (e.g., a Cas9 or a nucleobase editor) when two coding sequences are “in-frame with each other” and are translated as a single polypeptide fusing two sequences.
Nucleic acids of the present disclosure may include one or more genetic elements. A “genetic element” refers to a particular nucleotide sequence that has a role in nucleic acid expression (e.g., promoter, enhancer, terminator) or encodes a discrete product of an engineered nucleic acid (e.g., a nucleotide sequence encoding a guide RNA, a protein and/or an RNA interference molecule).
A “promoter” refers to a control region of a nucleic acid sequence at which initiation and rate of transcription of the remainder of a nucleic acid sequence are controlled. A promoter may also contain sub-regions at which regulatory proteins and molecules may bind, such as RNA polymerase and other transcription factors. Promoters may be constitutive, inducible, activatable, repressible, tissue-specific, or any combination thereof. A promoter drives expression or drives transcription of the nucleic acid sequence that it regulates. Herein, a promoter is considered to be “operably linked” when it is in a correct functional location and orientation in relation to a nucleic acid sequence it regulates to control (“drive”) transcriptional initiation and/or expression of that sequence.
A promoter may be one naturally associated with a gene or sequence, as may be obtained by isolating the 5′ non-coding sequences located upstream of the coding segment of a given gene or sequence. Such a promoter is referred to as an “endogenous promoter.” In some embodiments, a coding nucleic acid sequence may be positioned under the control of a recombinant or heterologous promoter, which refers to a promoter that is not normally associated with the encoded sequence in its natural environment. Such promoters may include promoters of other genes; promoters isolated from any other cell; and synthetic promoters or enhancers that are not “naturally occurring” such as, for example, those that contain different elements of different transcriptional regulatory regions and/or mutations that alter expression through methods of genetic engineering that are known in the art. In addition to producing nucleic acid sequences of promoters and enhancers synthetically, sequences may be produced using recombinant cloning and/or nucleic acid amplification technology, including polymerase chain reaction (PCR).
In some embodiments, promoters used in accordance with the present disclosure are “inducible promoters,” which are promoters that are characterized by regulating (e.g., initiating or activating) transcriptional activity when in the presence of, influenced by or contacted by an inducer signal. An inducer signal may be endogenous or a normally exogenous condition (e.g., light), compound (e.g., chemical or non-chemical compound) or protein that contacts an inducible promoter in such a way as to be active in regulating transcriptional activity from the inducible promoter. Thus, a “signal that regulates transcription” of a nucleic acid refers to an inducer signal that acts on an inducible promoter. A signal that regulates transcription may activate or inactivate transcription, depending on the regulatory system used. Activation of transcription may involve directly acting on a promoter to drive transcription or indirectly acting on a promoter by inactivation a repressor that is preventing the promoter from driving transcription. Conversely, deactivation of transcription may involve directly acting on a promoter to prevent transcription or indirectly acting on a promoter by activating a repressor that then acts on the promoter.
In genetics, a “sense” strand is the segment within double-stranded DNA that runs from 5′ to 3′, and which is complementary to the antisense strand of DNA, or template strand, which runs from 3′ to 5′. In the case of a DNA segment that encodes a protein, the sense strand is the strand of DNA that has the same sequence as the mRNA, which takes the antisense strand as its template during transcription, and eventually undergoes (typically, not always) translation into a protein. The antisense strand is thus responsible for the RNA that is later translated to protein, while the sense strand possesses a nearly identical makeup to that of the mRNA. Note that for each segment of dsDNA, there will possibly be two sets of sense and antisense, depending on which direction one reads (since sense and antisense is relative to perspective). It is ultimately the gene product, or mRNA, that dictates which strand of one segment of dsDNA is referred to as sense or antisense.
The term “subject,” as used herein, refers to an individual organism, for example, an individual mammal. In some embodiments, the subject is a human. In some embodiments, the subject is a non-human mammal. In some embodiments, the subject is a non-human primate. In some embodiments, the subject is a rodent. In some embodiments, the subject is a sheep, a goat, a cattle, a cat, or a dog. In some embodiments, the subject is a vertebrate, an amphibian, a reptile, a fish, an insect, a fly, or a nematode. In some embodiments, the subject is a research animal. In some embodiments, the subject is genetically engineered, e.g., a genetically engineered non-human subject. The subject may be of either sex and at any stage of development.
A subject in need thereof” refers to an individual who has a disease, a sign and/or symptom of a disease, or a predisposition toward a disease, with the purpose to cure, heal, alleviate, relieve, alter, remedy, ameliorate, improve, or affect the disease, the symptom of the disease, or the predisposition toward the disease. In some embodiments, the subject is a mammal. In some embodiments, the subject is a non-human primate. In some embodiments, the subject is human. In some embodiments, the mammal is a rodent. In some embodiments, the rodent is a mouse. In some embodiments, the rodent is a rat. In some embodiments, the mammal is a companion animal. A “companion animal” refers to pets and other domestic animals. Non-limiting examples of companion animals include dogs and cats; livestock, such as horses, cattle, pigs, sheep, goats, and chickens; and other animals, such as mice, rats, guinea pigs, and hamsters.
The term “target site” refers to a sequence within a nucleic acid molecule that is edited by a base editor (BE) or nucleobase editor disclosed herein. The term “target site,” in the context of a single strand, also can refer to the “target strand” which anneals or binds to the spacer sequence of the guide RNA. The target site can refer, in certain embodiments, to a segment of double-stranded DNA that includes the protospacer (i.e., the strand of the target site that has the same nucleotide sequence as the spacer sequence of the guide RNA) on the PAM-strand (or non-target strand) and target strand, which is complementary to the protospacer and the spacer alike, and which anneals to the spacer of the guide RNA, thereby targeting or programming a Cas9 nucleobase editor to target the target site.
A “transcriptional terminator” is a nucleic acid sequence that causes transcription to stop. A transcriptional terminator may be unidirectional or bidirectional. It is comprised of a DNA sequence involved in specific termination of an RNA transcript by an RNA polymerase. A transcriptional terminator sequence prevents transcriptional activation of downstream nucleic acid sequences by upstream promoters. A transcriptional terminator may be necessary in vivo to achieve desirable expression levels or to avoid transcription of certain sequences. A transcriptional terminator is considered to be “operably linked to” a nucleotide sequence when it is able to terminate the transcription of the sequence it is linked to.
The most commonly used type of terminator is a forward terminator. When placed downstream of a nucleic acid sequence that is usually transcribed, a forward transcriptional terminator will cause transcription to abort. In some embodiments, bidirectional transcriptional terminators are provided, which usually cause transcription to terminate on both the forward and reverse strand. In some embodiments, reverse transcriptional terminators are provided, which usually terminate transcription on the reverse strand only.
In prokaryotic systems, terminators usually fall into two categories (1) rho-independent terminators and (2) rho-dependent terminators. Rho-independent terminators are generally composed of palindromic sequence that forms a stem loop rich in G-C base pairs followed by several T bases. Without wishing to be bound by theory, the conventional model of transcriptional termination is that the stem loop causes RNA polymerase to pause, and transcription of the poly-A tail causes the RNA:DNA duplex to unwind and dissociate from RNA polymerase.
In eukaryotic systems, the terminator region may comprise specific DNA sequences that permit site-specific cleavage of the new transcript so as to expose a polyadenylation site. This signals a specialized endogenous polymerase to add a stretch of about 200 A residues (polyA) to the 3′ end of the transcript. RNA molecules modified with this polyA tail appear to more stable and are translated more efficiently. Thus, in some embodiments involving eukaryotes, a terminator may comprise a signal for the cleavage of the RNA. In some embodiments, the terminator signal promotes polyadenylation of the message. The terminator and/or polyadenylation site elements may serve to enhance output nucleic acid levels and/or to minimize read through between nucleic acids.
Terminators for use in accordance with the present disclosure include any terminator of transcription described herein or known to one of ordinary skill in the art. Examples of terminators include, without limitation, the termination sequences of genes such as, for example, the bovine growth hormone terminator, and viral termination sequences such as, for example, the SV40 terminator, spy, yejM, secG-leuU, thrLABC, rrnB T1, hisLGDCBHAFI, metZWV, rrnC, xapR, aspA and arcA terminator. In some embodiments, the termination signal may be a sequence that cannot be transcribed or translated, such as those resulting from a sequence truncation.
A “Woodchuck Hepatitis Virus (WHP) Posttranscriptional Regulatory Element (WPRE)” is a DNA sequence that, when transcribed creates a tertiary structure enhancing expression. Commonly used in molecular biology to increase expression of genes delivered by viral vectors. WPRE is a tripartite regulatory element with gamma, alpha, and beta components.
The full WPRE sequence is 609 bp long:
The terms “nucleic acid,” and “polynucleotide,” as used herein, refer to a compound comprising a nucleobase and an acidic moiety, e.g., a nucleotide, or a polymer of nucleotides. Typically, polymeric nucleic acids, e.g., nucleic acid molecules comprising three or more nucleotides are linear molecules, in which adjacent nucleotides are linked to each other via a phosphodiester linkage. In some embodiments, “nucleic acid” refers to individual nucleic acid residues (e.g. nucleotides and/or nucleosides). In some embodiments, “nucleic acid” refers to an oligonucleotide chain comprising three or more individual nucleotide residues. As used herein, the terms “oligonucleotide” and “polynucleotide” can be used interchangeably to refer to a polymer of nucleotides (e.g., a string of at least three nucleotides). In some embodiments, “nucleic acid” encompasses RNA as well as single and/or double-stranded DNA. Nucleic acids may be naturally occurring, for example, in the context of a genome, a transcript, an mRNA, tRNA, rRNA, siRNA, snRNA, a plasmid, cosmid, chromosome, chromatid, or other naturally occurring nucleic acid molecule. On the other hand, a nucleic acid molecule may be a non-naturally occurring molecule, e.g., a recombinant DNA or RNA, an artificial chromosome, an engineered genome (e.g., an engineered viral vector), an engineered vector, or fragment thereof, or a synthetic DNA, RNA, or DNA/RNA hybrid, optionally including non-naturally occurring nucleotides or nucleosides. Furthermore, the terms “nucleic acid,” “DNA,” “RNA,” and/or similar terms include nucleic acid analogs, e.g., analogs having other than a phosphodiester backbone. Nucleic acids can be purified from natural sources, produced using recombinant expression systems and optionally purified, chemically synthesized, etc. Where appropriate, e.g., in the case of chemically synthesized molecules, nucleic acids can comprise nucleoside analogs such as analogs having chemically modified bases or sugars, and backbone modifications. A nucleic acid sequence is presented in the 5′ to 3′ direction unless otherwise indicated. In some embodiments, a nucleic acid is or comprises natural nucleosides (e.g. adenosine, thymidine, guanosine, cytidine, uridine, deoxyadenosine, deoxythymidine, deoxyguanosine, and deoxycytidine); nucleoside analogs (e.g., 2-aminoadenosine, 2-thiothymidine, inosine, pyrrolo-pyrimidine, 3-methyl adenosine, 5-methylcytidine, 2-aminoadenosine, C5-bromouridine, C5-fluorouridine, C5-iodouridine, C5-propynyl-uridine, C5-propynyl-cytidine, C5-methylcytidine, 2-aminoadenosine, 7-deazaadenosine, 7-deazaguanosine, 8-oxoadenosine, 8-oxoguanosine, O(6)-methylguanine, and 2-thiocytidine); chemically modified bases; biologically modified bases (e.g., methylated bases); intercalated bases; modified sugars (e.g., 2′-fluororibose, ribose, 2′-deoxyribose, arabinose, and hexose); and/or modified phosphate groups (e.g., phosphorothioates and 5′-N-phosphoramidite linkages).
The terms “protein,” “peptide,” and “polypeptide” are used interchangeably herein, and refer to a polymer of amino acid residues linked together by peptide (amide) bonds. The terms refer to a protein, peptide, or polypeptide of any size, structure, or function. Typically, a protein, peptide, or polypeptide will be at least three amino acids long. A protein, peptide, or polypeptide may refer to an individual protein or a collection of proteins. One or more of the amino acids in a protein, peptide, or polypeptide may be modified, for example, by the addition of a chemical entity such as a carbohydrate group, a hydroxyl group, a phosphate group, a farnesyl group, an isofarnesyl group, a fatty acid group, a linker for conjugation, functionalization, or other modification, etc. A protein, peptide, or polypeptide may also be a single molecule or may be a multi-molecular complex. A protein, peptide, or polypeptide may be just a fragment of a naturally occurring protein or peptide. A protein, peptide, or polypeptide may be naturally occurring, recombinant, or synthetic, or any combination thereof. The term “fusion protein” as used herein refers to a hybrid polypeptide which comprises protein domains from at least two different proteins. One protein may be located at the amino-terminal (N-terminal) portion of the fusion protein or at the carboxy-terminal (C-terminal) protein thus forming an “amino-terminal fusion protein” or a “carboxy-terminal fusion protein,” respectively. A protein may comprise different domains, for example, a nucleic acid binding domain (e.g., the gRNA binding domain of Cas9 that directs the binding of the protein to a target site) and a nucleic acid cleavage domain or a catalytic domain of a nucleic-acid editing protein. In some embodiments, a protein is in a complex with, or is in association with, a nucleic acid, e.g., RNA or DNA. Any of the proteins provided herein may be produced by any method known in the art. For example, the proteins provided herein may be produced via recombinant protein expression and purification, which is especially suited for fusion proteins comprising a peptide linker. Methods for recombinant protein expression and purification are well known, and include those described by Green and Sambrook, Molecular Cloning: A Laboratory Manual (4th ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (2012)), which are incorporated herein by reference.
The term “subject,” as used herein, refers to an individual organism, for example, an individual mammal. In some embodiments, the subject is a human. In some embodiments, the subject is a non-human mammal. In some embodiments, the subject is a non-human primate. In some embodiments, the subject is a rodent (e.g., mouse, rat). In some embodiments, the subject is a domesticated animal. In some embodiments, the subject is a sheep, a goat, a cow, a cat, or a dog. In some embodiments, the subject is a research animal. In some embodiments, the subject is genetically engineered, e.g., a genetically engineered non-human subject. The subject may be of either sex and at any stage of development.
The term “recombinant” as used herein in the context of proteins or nucleic acids refers to proteins or nucleic acids that do not occur in nature, but are the product of human engineering. For example, in some embodiments, a recombinant protein or nucleic acid molecule comprises an amino acid or nucleotide sequence that comprises at least one, at least two, at least three, at least four, at least five, at least six, or at least seven mutations as compared to any naturally occurring sequence. The fusion proteins (e.g., nucleobase editors) described herein are made by recombinant technology. Recombinant technology is familiar to those skilled in the art.
The term “pharmaceutically-acceptable carrier” means a pharmaceutically-acceptable material, composition or vehicle, such as a liquid or solid filler, diluent, excipient, manufacturing aid (e.g., lubricant, talc magnesium, calcium or zinc stearate, or steric acid), or solvent encapsulating material, involved in carrying or transporting the compound from one site (e.g., the delivery site) of the body, to another site (e.g., organ, tissue or portion of the body). A pharmaceutically acceptable carrier is “acceptable” in the sense of being compatible with the other ingredients of the formulation and not injurious to the tissue of the subject (e.g., physiologically compatible, sterile, physiologic pH, etc.).
“A therapeutically effective amount” as used herein refers to the amount of each therapeutic agent (e.g., nucleobase editor, rAAV) described in the present disclosure required to confer therapeutic effect on the subject, either alone or in combination with one or more other therapeutic agents. Effective amounts vary, as recognized by those skilled in the art, depending on the particular condition being treated, the severity of the condition, the individual subject parameters including age, physical condition, size, gender, and weight, the duration of the treatment, the nature of concurrent therapy (if any), the specific route of administration and like factors within the knowledge and expertise of the health practitioner. These factors are well known to those of ordinary skill in the art and can be addressed with no more than routine experimentation. It is generally preferred that a maximum dose of the individual components or combinations thereof be used, that is, the highest safe dose according to sound medical judgment. It will be understood by those of ordinary skill in the art, however, that a subject may insist upon a lower dose or tolerable dose for medical reasons, psychological reasons or for virtually any other reasons. Empirical considerations, such as the half-life, generally will contribute to the determination of the dosage. For example, therapeutic agents that are compatible with the human immune system, such as polypeptides comprising regions from humanized antibodies or fully human antibodies, may be used to prolong half-life of the polypeptide and to prevent the polypeptide being attacked by the host's immune system.
The terms “treatment,” “treat,” and “treating,” refer to a clinical intervention aimed to reverse, alleviate, delay the onset of, or inhibit the progress of a disease or disorder, or one or more symptoms thereof, as described herein. As used herein, the terms “treatment,” “treat,” and “treating” refer to a clinical intervention aimed to reverse, alleviate, delay the onset of, or inhibit the progress of a disease or disorder, or one or more symptoms thereof, as described herein. In some embodiments, treatment may be administered after one or more symptoms have developed and/or after a disease has been diagnosed. In other embodiments, treatment may be administered in the absence of symptoms, e.g., to prevent or delay onset of a symptom or inhibit onset or progression of a disease. For example, treatment may be administered to a susceptible individual prior to the onset of symptoms (e.g., in light of a history of symptoms and/or in light of genetic or other susceptibility factors). Treatment may also be continued after symptoms have resolved, for example, to prevent or delay their recurrence.
As used herein, the term “variant” refers to a protein having characteristics that deviate from what occurs in nature that retains at least one functional i.e. binding, interaction, or enzymatic ability and/or therapeutic property thereof. A “variant” is at least about 70% identical, at least about 80% identical, at least about 90% identical, at least about 95% identical, at least about 96% identical, at least about 97% identical, at least about 98% identical, at least about 99% identical, at least about 99.5% identical, or at least about 99.9% identical to the wild type protein. For instance, a variant of Cas9 may comprise a Cas9 that has one or more changes in amino acid residues as compared to a wild type Cas9 amino acid sequence. As another example, a variant of a deaminase may comprise a deaminase that has one or more changes in amino acid residues as compared to a wild type deaminase amino acid sequence, e.g. following ancestral sequence reconstruction of the deaminase. These changes include chemical modifications, including substitutions of different amino acid residues truncations, covalent additions (e.g. of a tag), and any other mutations. The term also encompasses circular permutants, mutants, truncations, or domains of a reference sequence, and which display the same or substantially the same functional activity or activities as the reference sequence. This term also embraces fragments of a wild type protein.
The level or degree of which the property is retained may be reduced relative to the wild type protein but is typically the same or similar in kind. Generally, variants are overall very similar, and in many regions, identical to the amino acid sequence of the protein described herein. A skilled artisan will appreciate how to make and use variants that maintain all, or at least some, of a functional ability or property.
The variant proteins may comprise, or alternatively consist of, an amino acid sequence which is at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%, identical to, for example, the amino acid sequence of a wild-type protein, or any protein provided herein.
By a polypeptide having an amino acid sequence at least, for example, 95% “identical” to a query amino acid sequence, it is intended that the amino acid sequence of the subject polypeptide is identical to the query sequence except that the subject polypeptide sequence may include up to five amino acid alterations per each 100 amino acids of the query amino acid sequence. In other words, to obtain a polypeptide having an amino acid sequence at least 95% identical to a query amino acid sequence, up to 5% of the amino acid residues in the subject sequence may be inserted, deleted, or substituted with another amino acid. These alterations of the reference sequence may occur at the amino- or carboxy-terminal positions of the reference amino acid sequence or anywhere between those terminal positions, interspersed either individually among residues in the reference sequence or in one or more contiguous groups within the reference sequence.
As a practical matter, whether any particular polypeptide is at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identical to, for instance, the amino acid sequence of a protein such as a Niemann-Pick C1 (NPC1) protein, can be determined conventionally using known computer programs. A preferred method for determining the best overall match between a query sequence (a sequence of the present invention) and a subject sequence, also referred to as a global sequence alignment, can be determined using the FASTDB computer program based on the algorithm of Brutlag et al. (Comp. App. Biosci. 6:237-245 (1990)). In a sequence alignment the query and subject sequences are either both nucleotide sequences or both amino acid sequences. The result of said global sequence alignment is expressed as percent identity. Preferred parameters used in a FASTDB amino acid alignment are: Matrix=PAM 0, k-tuple=2, Mismatch Penalty=1, Joining Penalty=20, Randomization Group Length=0, Cutoff Score=1, Window Size=sequence length, Gap Penalty=5, Gap Size Penalty=0.05, Window Size=500 or the length of the subject amino acid sequence, whichever is shorter.
If the subject sequence is shorter than the query sequence due to N- or C-terminal deletions, not because of internal deletions, a manual correction must be made to the results. This is because the FASTDB program does not account for N- and C-terminal truncations of the subject sequence when calculating global percent identity. For subject sequences truncated at the N- and C-termini, relative to the query sequence, the percent identity is corrected by calculating the number of residues of the query sequence that are N- and C-terminal of the subject sequence, which are not matched/aligned with a corresponding subject residue, as a percent of the total bases of the query sequence. Whether a residue is matched/aligned is determined by results of the FASTDB sequence alignment. This percentage is then subtracted from the percent identity, calculated by the above FASTDB program using the specified parameters, to arrive at a final percent identity score. This final percent identity score is what is used for the purposes of the present invention. Only residues to the N- and C-termini of the subject sequence, which are not matched/aligned with the query sequence, are considered for the purposes of manually adjusting the percent identity score. That is, only query residue positions outside the farthest N- and C-terminal residues of the subject sequence.
The term “vector,” as used herein, refers to a nucleic acid that can be modified to encode a gene of interest and that is able to enter into a host cell and replicate within the host cell, and then transfer a replicated form of the vector into another host cell. Exemplary suitable vectors include viral vectors, such as AAV vectors or bacteriophages and filamentous phage, and conjugative plasmids. Additional suitable vectors will be apparent to those of skill in the art based on the instant disclosure.
As used herein the term “wild type” is a term of the art understood by skilled persons and means the typical form of an organism, strain, gene or characteristic as it occurs in nature as distinguished from mutant or variant forms.
Provided herein are nucleic acid molecules (e.g., vector genomes), compositions (containing, e.g., vectors, recombinant viruses), rAAV particles, and kits comprising nucleic acids encoding split napDNAbp domains (e.g., Cas9 proteins) or nucleobase editors, and methods of delivering a nucleobase editor or a napDNAbp domain into a cell using such nucleic acids. The N-terminal portion and C-terminal portion of a nucleobase editor or a napDNAbp domain are encoded on separate nucleic acids and delivered into a cell, e.g., a via recombinant adeno-associated virus (rAAV particles) delivery. In particular embodiments, the N-terminal portion of a nucleobase editor is fused to a first intein, and the C-terminal portion of a nucleobase editor is fused to an intein. The N-terminal and C-terminal portions may each be encoded on separate nucleic acids and delivered into a cell, e.g., a via rAAV particle delivery. The polypeptides corresponding to the N-terminal portion and C-terminal portion of the base editor (or nucleobase editor) may be joined to form a complete nucleobase editor or Cas9 protein, e.g., via intein-mediated protein splicing.
To overcome the packaging size limit and deliver base editors using AAVs, a split-base editor dual AAV strategy was devised, in which the CBE or ABE is divided into an N-terminal portion (or “half”) and a C-terminal half. Each base editor half is fused to half of a fast-splicing split-intein. Following co-infection by AAV particles expressing each base editor-split intein half, protein splicing in trans reconstitutes the full-length base editor. Unlike other approaches utilizing small molecules or sgRNA to bridge split Cas9, intein splicing removes all exogenous sequences and regenerates a native peptide bond at the split site, resulting in a single reconstituted protein (e.g., a protein that is identical in sequence to the unmodified nucleobase editor).
Split-intein CBEs and split-intein ABEs are disclosed that are integrated into dual AAV genomes to enable efficient base editing in somatic tissues of therapeutic relevance, including liver, heart, muscle, retina, and brain. The resulting AAVs were used to achieve base editing efficiencies at test loci for both CBEs and ABEs that, in each of these tissues, meets or exceeds therapeutically relevant editing thresholds for the treatment of human genetic diseases at AAV dosages that are known to be well-tolerated in humans. In particular, the disclosed AAV-nucleobase editor vectors achieved editing efficiencies of 59% editing (A.T-to-G.C) among unsorted cells in the cortex, and 48-50% editing (C.G-to-T.A) in photoreceptor cells and mouse embryonic fibroblasts (MEFs). The highest in vivo genome editing efficiencies were observed following injection of ˜1013-1014 vector genomes per kilogram weight of subject (vgs/kg), which is a dosage comparable to those currently used in human gene therapy trials. Accordingly, the invention provides split napDNAbp domains (e.g., Cas9 proteins), split nucleobase editors, and nucleic acids and vectors encoding same; as well as cells, compositions, methods, kits, and systems that utilize the disclosed split napDNAbp domains, split nucleobase editors, and vectors.
Aspects of the present disclosure relate to nucleic acid molecules encoding a N-terminal portion of a base editor or nucleobase editor fused at its C-terminus to a first intein sequence, wherein the nucleic acid molecule is operably linked to a first promoter, further comprising a nucleic acid segment encoding a guide RNA (gRNA) operably linked to a second promoter, wherein the direction of transcription of the nucleic acid segment is reversed relative to the direction of transcription of the nucleic acid molecule. These nucleic acid molecules may be comprised within a viral genome, such as an rAAV genome or rAAV vector.
Further provided are nucleic acid molecules encoding a C-terminal portion of a nucleobase editor fused at its N-terminus to an intein sequence, wherein the nucleic acid molecule is operably linked to a first promoter, and further comprising a nucleic acid segment encoding a guide RNA (gRNA) operably linked to a second promoter, wherein the direction of transcription of the nucleic acid segment is reversed relative to the direction of transcription of the nucleic acid molecule. In some embodiments, the first promoter of the nucleic acid molecule encoding the N-terminal portion of the nucleobase editor and the first promoter of the nucleic acid molecule encoding the C-terminal portion of the nucleobase editor comprise the same promoter (i.e., are the same). In other embodiments, these first promoters are different. In some embodiments, the second promoter of the nucleic acid molecule encoding the N-terminal portion of the nucleobase editor and the second promoter of the nucleic acid molecule encoding the C-terminal portion of the nucleobase editor are the same. In other embodiments, these second promoters are different.
Some aspects of the present disclosure relate to compositions comprising (i) a first nucleotide sequence encoding an N-terminal portion of a Cas9 protein fused at its C-terminus to an intein-N; and (ii) a second nucleotide sequence encoding an intein-C fused to the N-terminus of a C-terminal portion of the Cas9 protein, wherein at least one of the first nucleotide sequence and second nucleotide sequence comprises at its 3′ end a gRNA nucleic acid segment encoding a guide RNA (gRNA) operably linked to a second promoter, and wherein the direction of transcription of the gRNA nucleic acid segment is reversed relative to the direction of transcription of the at least one nucleotide sequence. In some embodiments, the first nucleotide sequence and/or second nucleotide sequence is operably linked to a nucleotide sequence encoding at least one bipartite nuclear localization signal (NLS).
Additional aspects of the present disclosure relate to methods of editing using the split nucleobase editors and/or the split Cas9 proteins disclosed herein. In particular embodiments, provided herein are methods of base editing at therapeutically-relevant efficiencies in vivo, such as in murine retina. The methods disclosed herein improve the rate and throughput with which promising base editor targets can be identified in cultured cells and in vivo.
This disclosure describes methods of base editing that may be used for targeted editing of DNA in vitro, e.g., for the generation of mutant cells or animals; for the introduction of targeted mutations, e.g., for the correction of genetic defects in cells ex vivo, e.g., in cells obtained from a subject that are subsequently re-introduced into the same or another subject; and for the introduction of targeted mutations in vivo, e.g., the correction of genetic defects or the introduction of deactivating mutations in disease-associated genes in a subject. As an example, diseases and conditions can be treated by making an A to G, or a C to T mutation, may be treated using the base editors provided herein. The base editors described herein may be utilized for the targeted editing of C to T and G to A mutations so as to correct a mutation or restore a normal reading frame in an gene to generate a functional protein. In certain embodiments, the subject has been diagnosed with a disease, disorder, or condition, such as, but not limited to, a disease, disorder, or condition associated with a point mutation in the Tmc1 gene or the NPC1 gene. The methods described herein involving contacting a base editor with a target nucleotide sequence in the genome of an organism, e.g., a human.
In certain embodiments, the methods described above result in cutting (or nicking) one strand of the double-stranded DNA, for example, the strand that includes the thymine (T) of a target A:T nucleobase pair opposite the strand containing the target adenine (A) that is being deaminated. This nicking result serves to direct mismatch repair machinery to the non-edited strand, ensuring that the chemically modified nucleobase is not interpreted as a lesion by the machinery. This nick may be created by the use of an nCas9.
Still further, the present disclosure provides for methods of making the disclosed split nucleobase editors, as well as methods of using the split nucleobase editors or nucleic acid molecules encoding the nucleobase editors in applications including editing a nucleic acid molecule, e.g., a genome. Such methods involve transducing (e.g., via transfection) cells with a plurality of complexes each comprising a portion of a split nucleobase editor (e.g., a nucleobase editor comprising a napDNAbp (e.g., nCas9) domain and a deaminase domain) and/or a gRNA molecule. In some embodiments, the nucleic acid constructs encoding the N-terminal and C-terminal portions of the split nucleobase editor are transfected separately from one another. In certain embodiments, the methods involve the transfection of nucleic acid constructs (e.g., plasmids) that each (or together) encode the components of a complex of split nucleobase editor and a gRNA molecule.
In certain embodiments of the disclosed methods of making the disclosed split nucleobase editors, one or more nucleic acid constructs that encode the split nucleobase editor is transfected into the cell separately from the plasmid that encodes the gRNA molecule. In certain embodiments, these components are encoded on a single construct and transfected together. In other embodiments, the methods disclosed herein involve the introduction into cells of one or more nucleic acid vectors encoding a a split nucleobase editor and gRNA molecule that has been expressed and cloned outside of these cells. In some embodiments, these vectors are delivered as part of an rAAV vector.
It should be appreciated that any nucleobase editor, e.g., any of the nucleobase editors provided herein, may be introduced into the cell in any suitable way, either stably or transiently. In some embodiments, a nucleobase editor may be transfected into the cell. In some embodiments, the cell may be transduced or transfected with a nucleic acid construct that encodes a nucleobase editor. For example, a cell may be transduced (e.g., with a virus encoding a nucleobase editor), or transfected (e.g., with a plasmid encoding a nucleobase editor) with a nucleic acid that encodes a nucleobase editor, or the translated nucleobase editor. Such transduction may be a stable or transient transduction. In some embodiments, cells expressing a nucleobase editor or containing a nucleobase editor may be transduced or transfected with one or more gRNA molecules, for example, when the nucleobase editor comprises a Cas9 (e.g., nCas9) domain. In some embodiments, a plasmid expressing one or more portions of a nucleobase editor may be introduced into cells through electroporation, transient (e.g., lipofection) and stable genome integration (e.g., nucleofection and piggybac), viral transduction, or other methods known to those of skill in the art. In particular embodiments, plasmids expressing one or more portions of any of the disclosed nucleobase editors may be delivered to cells through nucleofection.
In some aspects, the disclosed split nucleobase editors are delivered to the cell (or the subject) by use of recombinant AAV (rAAV) particles. In some embodiments, any of the disclosed split nucleobase editors is fused to split intein pairs that are packaged into two separate rAAV particles that, when co-delivered to a cell, reconstitute the functional editor protein. Several other considerations to account for the unique features of base editing are described, including the optimization of second-site nicking targets and properly packaging nucleobase editors into virus vectors, including lentiviruses and rAAV. Accordingly, the disclosure provides dual rAAV vectors and dual rAAV vector particles that comprise expression constructs that encode two portions (or “two halves”) of any of the disclosed nucleobase editors, wherein the encoded nucleobase editor is divided between the two halves at a split site. In some embodiments, the disclosed rAAV vectors encoding the split nucleobase editors may comprise a nucleotide sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the sequences depicted in
Accordingly, the present disclosure provides compositions comprising: (i) a first recombinant adeno associated virus (rAAV) particle comprising a first nucleotide sequence encoding a N-terminal portion of a Cas9 protein fused at its C-terminus to an intein-N; and (ii) a second recombinant adeno associated virus (rAAV) particle comprising a second nucleotide sequence encoding an intein-C fused to the N-terminus of a C-terminal portion of the Cas9 protein. In some embodiments, at least one of the first nucleotide sequence and second nucleotide sequence comprises at its 3′ end a gRNA nucleic acid segment encoding a guide RNA (gRNA) operably linked to a second promoter, and wherein the direction of transcription of the gRNA nucleic acid segment is reversed relative to the direction of transcription of the at least one nucleotide sequence.
In some aspects, the specification discloses a pharmaceutical composition comprising any one of the presently disclosed complexes of nucleobase editors and gRNA. In other aspects, the present disclosure discloses a pharmaceutical composition comprising one or more polynucleotides encoding the nucleobase editors disclosed herein and one or more polynucleotides encoding a gRNA, or polynucleotides encoding both. The one or more polynucleotides encoding the nucleobase editors and one or moe polynucleotides encoding a gRNA may be provided on the same vector, or different vectors (e.g., different rAAV vectors).
napDNAbp Domains
In some aspects, the base editing methods and nucleobase editors described herein involve a nucleic acid programmable DNA binding protein (napDNAbp). Each napDNAbp is associated with at least one guide nucleic acid (e.g., guide RNA), which localizes the napDNAbp to a DNA sequence that comprises a DNA strand (i.e., a target strand) that is complementary to the guide nucleic acid, or a portion thereof (e.g., the protospacer of a guide RNA). In other words, the guide nucleic-acid “programs” the napDNAbp (e.g., Cas9 or equivalent) to localize and bind to a complementary sequence. In various embodiments, the napDNAbp can be fused to a disclosed herein adenosine deaminase or a herein disclosed cytosine deaminase. In other aspects, the napDNAbp can be fused to a non-deaminase nucleobase modifying enzyme (or nucleobase modification domain) disclosed herein.
Without being bound by theory, the binding mechanism of a napDNAbp—guide RNA complex, in general, includes the step of forming an R-loop whereby the napDNAbp induces the unwinding of a double-strand DNA target, thereby separating the strands in the region bound by the napDNAbp. The guide RNA spacer then hybridizes to the “target strand.” This displaces a “non-target strand” that is complementary to the target strand, which forms the single strand region of the R-loop. In some embodiments, the napDNAbp includes one or more nuclease activities, which then cut the DNA leaving various types of lesions. For example, the napDNAbp may comprises a nuclease activity that cuts the non-target strand at a first location, and/or cuts the target strand at a second location. Depending on the nuclease activity, the target DNA can be cut to form a “double-stranded break” whereby both strands are cut. In other embodiments, the target DNA can be cut at only a single site, i.e., the DNA is “nicked” on one strand. Exemplary napDNAbp with different nuclease activities include “Cas9 nickase” (“nCas9”) and a deactivated Cas9 having no nuclease activities (“dead Cas9” or “dCas9”).
The below description of various napDNAbps which can be used in connection with the presently disclose nucleobase editors is not meant to be limiting in any way. The nucleobase editors may comprise the canonical SpCas9, or any ortholog Cas9 protein, or any variant Cas9 protein—including any naturally occurring variant, mutant, or otherwise engineered version of Cas9—that is known or which can be made or evolved through a directed evolutionary or otherwise mutagenic process. In various embodiments, the Cas9 or Cas9 variants have a nickase activity, i.e., only cleave of strand of the target DNA sequence. In other embodiments, the Cas9 or Cas9 variants have inactive nucleases, i.e., are “dead” Cas9 proteins. Other variant Cas9 proteins that may be used are those having a smaller molecular weight than the canonical SpCas9 (e.g., for easier delivery) or having modified or rearranged primary amino acid structure (e.g., the circular permutant formats). The nucleobase editors described herein may also comprise Cas9 equivalents, including Cas12a/Cpf1 and Cas12b proteins which are the result of convergent evolution. The napDNAbps used herein (e.g., SpCas9, Cas9 variant, or Cas9 equivalents) may also may also contain various modifications that alter/enhance their PAM specificities. Lastly, the application contemplates any Cas9, Cas9 variant, or Cas9 equivalent which has at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.9% sequence identity to a reference Cas9 sequence, such as a references SpCas9 canonical sequence or a reference Cas9 equivalent (e.g., Cas12a/Cpf1).
The napDNAbp can be a CRISPR (clustered regularly interspaced short palindromic repeat)-associated nuclease. As outlined above, CRISPR is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain spacers, sequences complementary to antecedent mobile elements, and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). In type II CRISPR systems correct processing of pre-crRNA requires a trans-encoded small RNA (tracrRNA), endogenous ribonuclease 3 (rnc) and a Cas9 protein. The tracrRNA serves as a guide for ribonuclease 3-aided processing of pre-crRNA. Subsequently, Cas9/crRNA/tracrRNA endonucleolytically cleaves linear or circular dsDNA target complementary to the spacer. The target strand not complementary to crRNA is first cut endonucleolytically, then trimmed 3′-5′ exonucleolytically. In nature, DNA-binding and cleavage typically requires protein and both RNAs. However, single guide RNAs (“sgRNA”, or simply “gRNA”) can be engineered so as to incorporate aspects of both the crRNA and tracrRNA into a single RNA species. See, e.g., Jinek M. et al., Science 337:816-821(2012), the entire contents of which is hereby incorporated by reference.
In some embodiments, the napDNAbp directs cleavage of one or both strands at the location of a target sequence, such as within the target sequence and/or within the complement of the target sequence. In some embodiments, the napDNAbp directs cleavage of one or both strands within about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 200, 500, or more base pairs from the first or last nucleotide of a target sequence. In some embodiments, a vector encodes a napDNAbp that is mutated to with respect to a corresponding wild-type enzyme such that the mutated napDNAbp lacks the ability to cleave one or both strands of a target polynucleotide containing a target sequence. For example, an aspartate-to-alanine substitution (D10A) in the RuvC I catalytic domain of Cas9 from S. pyogenes converts Cas9 from a nuclease that cleaves both strands to a nickase (cleaves a single strand). Other examples of mutations that render Cas9 a nickase include, without limitation, H840A, N854A, and N863A in reference to the canonical SpCas9 sequence, or to equivalent amino acid positions in other Cas9 variants or Cas9 equivalents.
As used herein, the term “Cas protein” refers to a full-length Cas protein obtained from nature, a recombinant Cas protein having a sequences that differs from a naturally occurring Cas protein, or any fragment of a Cas protein that nevertheless retains all or a significant amount of the requisite basic functions needed for the disclosed methods, i.e., (i) possession of nucleic-acid programmable binding of the Cas protein to a target DNA, and (ii) ability to nick the target DNA sequence on one strand. The Cas proteins contemplated herein embrace CRISPR Cas 9 proteins, as well as Cas9 equivalents, variants (e.g., Cas9 nickase (nCas9) or nuclease inactive Cas9 (dCas9)) homologs, orthologs, or paralogs, whether naturally occurring or non-naturally occurring (e.g., engineered or recombinant), and may include a Cas9 equivalent from any type of CRISPR system (e.g., type II, V, VI), including Cpf1 (a type-V CRISPR-Cas systems), C2c1 (a type V CRISPR-Cas system), C2c2 (a type VI CRISPR-Cas system) and C2c3 (a type V CRISPR-Cas system). Further Cas-equivalents are described in Makarova et al., “C2c2 is a single-component programmable RNA-guided RNA-targeting CRISPR effector,” Science 2016; 353(6299), the contents of which are incorporated herein by reference.
The terms “Cas9” or “Cas9 nuclease” or “Cas9 moiety” or “Cas9 domain” embrace any naturally occurring Cas9 from any organism, any naturally-occurring Cas9 equivalent or functional fragment thereof, any Cas9 homolog, ortholog, or paralog from any organism, and any mutant or variant of a Cas9, naturally-occurring or engineered. The term Cas9 is not meant to be particularly limiting and may be referred to as a “Cas9 or equivalent.” Exemplary Cas9 proteins are further described herein and/or are described in the art and are incorporated herein by reference. The present disclosure is unlimited with regard to the particular Cas9 that is employed in the nucleobase editor (BE) of the invention.
As noted herein, Cas9 nuclease sequences and structures are well known to those of skill in the art (see, e.g., “Complete genome sequence of an M1 strain of Streptococcus pyogenes.” Ferretti et al., J. J., McShan W. M., Ajdic D. J., Savic D. J., Savic G., Lyon K., Primeaux C., Sezate S., Suvorov A. N., Kenton S., Lai H. S., Lin S. P., Qian Y., Jia H. G., Najar F. Z., Ren Q., Zhu H., Song L., White J., Yuan X., Clifton S. W., Roe B. A., McLaughlin R. E., Proc. Natl. Acad. Sci. U.S.A. 98:4658-4663(2001); “CRISPR RNA maturation by trans-encoded small RNA and host factor RNase III.” Deltcheva E., Chylinski K., Sharma C. M., Gonzales K., Chao Y., Pirzada Z. A., Eckert M. R., Vogel J., Charpentier E., Nature 471:602-607(2011); and “A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity.” Jinek M., Chylinski K., Fonfara I., Hauer M., Doudna J. A., Charpentier E. Science 337:816-821(2012), the entire contents of each of which are incorporated herein by reference).
The Cas9 protein encoded by the first and second nucleotide sequence is herein referred as a “split Cas9.” The Cas9 protein is known to have an N-terminal lobe and a C-terminal lobe linked by a disordered linker (e.g., as described in Nishimasu et al., Cell, Volume 156, Issue 5, pp. 935-949, 2014, incorporated herein by reference). In some embodiments, the N-terminal portion of the split Cas9 protein comprises the N-terminal lobe of a Cas9 protein. In some embodiments, the C-terminal portion of the split Cas9 comprises the C-terminal lobe of a Cas9 protein.
In some embodiments, the N-terminal portion of the split Cas9 comprises a portion of any one of SEQ ID NO: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 1-(550-650) in SEQ ID NO: 1. “1-(550-650)” means starting from amino acid 1 and ending anywhere between amino acid 550-650 (inclusive). For example, the N-terminal portion of the split Cas9 may comprise a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 1-550, 1-551, 1-552, 1-553, 1-554, 1-555, 1-556, 1-557, 1-558, 1-559, 1-560, 1-561, 1-562, 1-563, 1-564, 1-565, 1-566, 1-567, 1-568, 1-569, 1-570, 1-571, 1-572, 1-573, 1-574, 1-575, 1-576, 1-577, 1-578, 1-579, 1-580, 1-581, 1-582, 1-583, 1-584, 1-585, 1-586, 1-587, 1-588, 1-589, 1-590, 1-591, 1-592, 1-593, 1-594, 1-595, 1-596, 1-597, 1-598, 1-599, 1-600, 1-601, 1-602, 1-603, 1-604, 1-605, 1-606, 1-607, 1-608, 1-609, 1-610, 1-611, 1-612, 1-613, 1-614, 1-615, 1-616, 1-617, 1-618, 1-619, 1-620, 1-621, 1-622, 1-623, 1-624, 1-625, 1-626, 1-627, 1-628, 1-629, 1-630, 1-631, 1-632, 1-633, 1-634, 1-635, 1-636, 1-637, 1-638, 1-639, 1-640, 1-641, 1-642, 1-643, 1-644, 1-645, 1-646, 1-647, 1-648, 1-649, or 1-650 of SEQ ID NO: 1. In some embodiments, the N-terminal portion of the split Cas9 protein comprises a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 1-573 or 1-637 of SEQ ID NO: 1.
In some embodiments, the N-terminal portion of the split Cas9 may comprise a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 1-430, 1-431, 1-432, 1-433, 1-434, 1-435, 1-436, 1-437, 1-438, 1-439, 1-440, 1-441, 1-442, 1-443, 1-444, 1-445, 1-446, 1-447, 1-448, 1-449, 1-450, 1-451, 1-452, 1-453, 1-454, 1-455, 1-456, 1-457, 1-458, 1-459, 1-460, 1-461, 1-462, 1-463, 1-464, 1-465, 1-466, 1-467, 1-468, 1-469, 1-470, 1-471, 1-472, 1-473, 1-474, 1-475, 1-476, 1-477, 1-478, 1-479, 1-480, 1-481, 1-482, 1-483, 1-484, 1-485, 1-486, 1-487, 1-488, 1-489, 1-490, 1-491, 1-492, 1-493, 1-494, 1-495, 1-496, 1-497, 1-498, 1-499, 1-500, 1-501, 1-502, 1-503, 1-504, 1-505, 1-506, 1-507, 1-508, 1-509, 1-510, 1-511, 1-512, 1-513, 1-514, 1-515, 1-516, 1-517, 1-518, 1-519, 1-520, 1-521, 1-522, 1-523, 1-524, 1-525, 1-526, 1-527, 1-528, 1-529, 1-530, 1-531, 1-532, 1-533, 1-534, 1-535, 1-536, 1-537, 1-538, or 1-539 of SEQ ID NO: 11. In some embodiments, the N-terminal portion of the split Cas9 protein comprises a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 1-431, 1-453, 1-457, 1-484, 1-501, 1-534, or 1-537 of SEQ ID NO: 11. In certain embodiments, the N-terminal portion of the split Cas9 protein comprises a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 1-534 of SEQ ID NO: 11.
The C-terminal portion of the split Cas9 can be joined with the N-terminal portion of the split Cas9 to form a complete Cas9 protein. In some embodiments, the C-terminal portion of the Cas9 protein starts from where the N-terminal portion of the Cas9 protein ends. As such, in some embodiments, the C-terminal portion of the split Cas9 comprises a portion of any one of SEQ ID NO: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids (551-651)-1368 of SEQ ID NO: 1. “(551-651)-1368” means starting at an amino acid between amino acids 551-651 (inclusive) and ending at amino acid 1368.
For example, the C-terminal portion of the split Cas9 may comprise a portion of any one of SEQ ID NO: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acid 551-1368, 552-1368, 553-1368, 554-1368, 555-1368, 556-1368, 557-1368, 558-1368, 559-1368, 560-1368, 561-1368, 562-1368, 563-1368, 564-1368, 565-1368, 566-1368, 567-1368, 568-1368, 569-1368, 570-1368, 571-1368, 572-1368, 573-1368, 574-1368, 575-1368, 576-1368, 577-1368, 578-1368, 579-1368, 580-1368, 581-1368, 582-1368, 583-1368, 584-1368, 585-1368, 586-1368, 587-1368, 588-1368, 589-1368, 590-1368, 591-1368, 592-1368, 593-1368, 594-1368, 595-1368, 596-1368, 597-1368, 598-1368, 599-1368, 600-1368, 601-1368, 602-1368, 603-1368, 604-1368, 605-1368, 606-1368, 607-1368, 608-1368, 609-1368, 610-1368, 611-1368, 612-1368, 613-1368, 614-1368, 615-1368, 616-1368, 617-1368, 618-1368, 619-1368, 620-1368, 621-1368, 622-1368, 623-1368, 624-1368, 625-1368, 626-1368, 627-1368, 628-1368, 629-1368, 630-1368, 631-1368, 632-1368, 633-1368, 634-1368, 635-1368, 636-1368, 637-1368, 638-1368, 639-1368, 640-1368, 641-1368, 642-1368, 643-1368, 644-1368, 645-1368, 646-1368, 647-1368, 648-1368, 649-1368, 650-1368, or 651-1368 of SEQ ID NO: 1. In some embodiments, the C-terminal portion of the split Cas9 protein comprises a portion of any one of SEQ ID NO: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 574-1368 or 638-1368 of SEQ ID NO: 1.
In other embodiments, the C-terminal portion of the split Cas9 protein comprises a portion of any one of SEQ ID NO: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 432-1054, 454-1054, 458-1054, 485-1054, 502-1054, 535-1054, or 538-1054 of SEQ ID NO: 11. In certain embodiments, the C-terminal portion of the split Cas9 protein comprises a portion of any one of SEQ ID NO: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 535-1054 of SEQ ID NO: 11.
In other embodiments, the C-terminal portion of the split Cas9 protein comprises a portion of any one of SEQ ID NO: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 432-1054, 454-1054, 458-1054, 485-1054, 502-1054, 535-1054, or 538-1054 of SEQ ID NO: 10. In certain embodiments, the C-terminal portion of the split Cas9 protein comprises a portion of any one of SEQ ID NO: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 535-1054 of SEQ ID NO: 10.
Further aspects of the present disclosure provide rAAV particles comprising a first nucleic acid molecule (e.g. encoding a N-terminal portion of a nucleobase editor or Cas9 protein fused at its C-terminus to an intein-N) as described herein. rAAV particles comprising a second nucleic acid molecule (e.g. encoding an intein-C fused to the N-terminus of a C-terminal portion of the Cas9 protein or nucleobase editor) as described herein are also provided. The disclosed rAAV particles may comprise both a first nucleic acid molecule and second nucleic acid molecules as described herein.
Cas9 variants may also be delivered to cells using the methods described herein. For example, a Cas9 variant may also be “split” as described herein. A Cas9 variant may comprise an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the Cas9 sequences provided herein. In some embodiments, the Cas9 variant comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 30%, no more than 25%, no more than 20%, no more than 15%, no more than 10%, no more than 5%, no more than 1% longer or shorter) than any of the Cas9 proteins provided herein (e.g., a S. pyogenes Cas9 (SpCas9) (SEQ ID NO: 1), S. pyogenes Cas9 nickase (SpCas9n) (SEQ ID NO: 3), S. aureus Cas9 (SaCas9) (SEQ ID NO: 10), and S. aureus Cas9 nickase (SaCas9) (SEQ ID NO: 11). In some embodiments, the Cas9 variant comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 200 amino acids, no more than 150 amino acids, no more than 100 amino acids, no more than 50 amino acids, no more than 10 amino acids, no more than 5 amino acids, or no more than 2 amino acids longer or shorter) than any of the Cas9 proteins provided herein.
In some embodiments, the N-terminal portion of a split Cas9 comprises an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to the corresponding portion of any one of the Cas9 sequences provided herein (e.g., a SpCas9, SpCas9n, SaCas9, or SaCas9n). In some embodiments, the N-terminal portion of the split Cas9 comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 30%, no more than 25%, no more than 20%, no more than 15%, no more than 10%, no more than 5%, no more than 1% longer or shorter) than the corresponding portion of any of the Cas9 proteins provided herein. In some embodiments, the N-terminal portion of the split Cas9 comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 200 amino acids, no more than 150 amino acids, no more than 100 amino acids, no more than 50 amino acids, no more than 10 amino acids, no more than 5 amino acids, or no more than 2 amino acids longer or shorter) than the corresponding portion of any of the Cas9 proteins provided herein.
In some embodiments, the C-terminal portion of a split Cas9 comprises an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to the corresponding portion of any one of the Cas9 sequences provided herein (e.g., the Cas9 sequences of any of SEQ ID NOs: 1, 3, 10, and 11). In some embodiments, the C-terminal portion of the split Cas9 comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 30%, no more than 25%, no more than 20%, no more than 15%, no more than 10%, no more than 5%, no more than 1% longer or shorter) than the corresponding portion of any of the Cas9 proteins provided herein. In some embodiments, the C-terminal portion of the split Cas9 comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 200 amino acids, no more than 150 amino acids, no more than 100 amino acids, no more than 50 amino acids, no more than 10 amino acids, no more than 5 amino acids, or no more than 2 amino acids longer or shorter) than the corresponding portion of any of the Cas9 proteins provided herein.
In some embodiments, the Cas9 variant is a dCas9 or nCas9. In some embodiments, the Cas9 protein is selected from S. pyogenes Cas9 (SpCas9) (SEQ ID NO: 1), S. pyogenes Cas9 nickase (SEQ ID NO: 3), S. aureus Cas9 (SaCas9) (SEQ ID NO: 10), and S. aureus Cas9 nickase (SEQ ID NO: 11). In certain embodiments, the Cas9 variant is a VRQR variant of SpCas9 that is compatible with NGA PAM sites.
Accordingly, in some embodiments, the N-terminal portion of the Cas9 protein comprises a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 1-573 or 1-637 of SEQ ID NO: 1. In some embodiments, the C-terminal portion of the Cas9 protein comprises a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 574-1368 or 638-1368 of SEQ ID NO: 1. In other embodiments, the N-terminal portion of the Cas9 protein comprises a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 1-573 or 1-637 of SEQ ID NO: 3. In some embodiments, the C-terminal portion of the Cas9 protein comprises a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 574-1368 or 638-1368 of SEQ ID NO: 3.
In some embodiments, the N-terminal portion of the Cas9 protein comprises a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 1-534 of SEQ ID NO: 11. In some embodiments, the C-terminal portion of the Cas9 protein comprises a portion of any one of SEQ ID NOs: 1-129, 143-275, 282-291, 394-397, 435-437, 519-549, and 554-556 that corresponds to amino acids 535-1054 of SEQ ID NO: 11.
In some embodiments, the N-terminal portion of the split Cas9 comprises a mutation corresponding to a D10A mutation in SEQ ID NO: 1. In some embodiments, the N-terminal portion of the split Cas9 comprises a mutation corresponding to a D10A mutation in SEQ ID NO: 1 and the C-terminal portion of the split Cas9 comprises a mutation corresponding to a H840A mutation in SEQ ID NO:1. In some embodiments, the N-terminal portion of the split Cas9 comprises a mutation corresponding to a D10A mutation in SEQ ID NO: 1, and the C-terminal portion of the split Cas9 comprises a histidine at the position corresponding to position 840 in SEQ ID NO:1.
In other embodiments, the N-terminal portion of the split Cas9 comprises a mutation corresponding to a D10A mutation in SEQ ID NO: 10.
In some embodiments, to join the N-terminal portion of the Cas9 protein and the C-terminal portion of the Cas9 protein, an intein system may be used. In some embodiments, the N-terminal portion of the Cas9 is fused to an intein-N. In some embodiments, the intein-N is fused to the C-terminus of the N-terminal portion of the Cas9 to form a structure of NH2-[N-terminal portion of Cas9]-[intein-N]-COOH. In some embodiments, the intein-N is encoded by the dnaE-n gene. In some embodiments, the intein-N comprises the amino acid sequence as set forth in SEQ ID NO: 351 or 355. In some embodiments, the C-terminal portion of the Cas9 is fused to an intein-C, and the intein-C is fused to the N-terminus of the C-terminal portion of the Cas9 to form a structure of NH2-[intein-C]-[C-terminal portion of Cas9]-COOH. In some embodiments, the intein-C is encoded by the dnaE-c gene. In some embodiments, the intein-C comprises the amino acid sequence as set forth in SEQ ID NO: 353 or 357.
Other split intein systems may also be used in the present disclosure and are known in the art. For example, in some embodiments, the intein pair comprises an Npu split intein. In certain such embodiments, the intein-N comprises the amino acid sequence of SEQ ID NO: 351. In some embodiments, the intein-C comprises the amino acid sequence of SEQ ID NO: 353.
As described herein, the N-terminal portion of a nucleobase editor comprises the N-terminal portion of a nuclease-inactive Cas9 protein (dCas9) or a Cas9 nickase (nCas9). In some embodiments, the N-terminal portion of a nucleobase editor further comprises a nucleobase modifying enzyme (e.g., nucleases, nickases, recombinases, deaminases, DNA repair enzymes, DNA damage enzymes, dismutases, alkylation enzymes, depurination enzymes, oxidation enzymes, pyrimidine dimer forming enzymes, integrases, transposases, polymerases, ligases, helicases, photolyases, glycosylases, epigenetic modifiers such as methylases, acetylases, methyltransferase, demethylase, etc.). In some embodiments, the nucleobase modifying enzyme is a deaminase (e.g., a cytosine deaminase or an adenosine deaminase, or functional variants thereof). In some embodiments, the nucleobase modifying enzyme is fused to the N-terminus of the N-terminal portion of the split dCas9 or split nCas9. In some embodiments, the N-terminal portion of the nucleobase editor has of the structure: NH2-[nucleobase modifying enzyme]-[N-terminal portion of dCas9 or nCas9]-COOH. In some embodiments, the N-terminal portion of the nucleobase editor is fused to an intein N. In some embodiments, the intein-N is fused to the C-terminus of the N-terminal portion of the nucleobase editor.
In some embodiments, the first nucleotide sequence encodes a polypeptide comprising the structure NH2-[nucleobase modifying enzyme]-[N-terminal portion of dCas9 or nCas9]-[intein-N]-COOH.
In some embodiments, the C-terminal portion of the nucleobase editor comprises the C-terminal portion of a nuclease-inactive Cas9 protein (dCas9) or a Cas9 nickase (nCas9). In some embodiments, the nucleobase modifying enzyme is fused to the C-terminus of the C-terminal portion of the split dCas9 or split nCas9. In some embodiments, the C-terminal portion of the nucleobase editor is of the structure: NH2-[C-terminal portion of dCas9 or nCas9]-[nucleobase modifying enzyme]-COOH. In some embodiments, the C-terminal portion of the nucleobase editor comprises an intein-C fused to the C-terminal portion of the Cas9 protein. In some embodiments, the intein-C is fused to the N-terminus of the C-terminal portion of the nucleobase editor. In some embodiments, the second nucleotide sequence encodes a polypeptide of the structure: NH2-[intein-C]-[C-terminal portion of the Cas9 protein]-COOH.
Non-limiting examples of suitable Cas9 proteins and variants, and nucleobase editors and variants are provided. The disclosure provides Cas9 variants, for example, Cas9 proteins from one or more organisms, which may comprise one or more mutations (e.g., to generate dCas9 or Cas9 nickase). In some embodiments, one or more of the amino acid residues, identified below by an asterisk, of a Cas9 protein may be mutated. In some embodiments, the D10 and/or H840 residues of the amino acid sequence provided in SEQ ID NO: 1, or a corresponding mutation in any of the amino acid sequences provided in SEQ ID NOs: 2-275, 394-397 and 488, are mutated. In some embodiments, the D10 residue of the amino acid sequence provided in SEQ ID NO: 1, or a corresponding mutation in any of the amino acid sequences provided in SEQ ID NOs: 2-275, 394-397 and 488, is mutated to any amino acid residue, except for D. In some embodiments, the D10 residue of the amino acid sequence provided in SEQ ID NO: 1, or a corresponding mutation in any of the amino acid sequences provided in SEQ ID NOs: 2-275, 394-397 and 488, is mutated to an A. In some embodiments, the H840 residue of the amino acid sequence provided in SEQ ID NO: 1, or a corresponding residue in any of the amino acid sequences provided in SEQ ID NOs: 2-275, 394-397 and 488, is an H. In some embodiments, the H840 residue of the amino acid sequence provided in SEQ ID NO: 1, or a corresponding mutation in any of the amino acid sequences provided in SEQ ID NOs: 2-275, 394-397 and 488, is mutated to any amino acid residue, except for H. In some embodiments, the H840 residue of the amino acid sequence provided in SEQ ID NO: 1, or a corresponding mutation in any of the amino acid sequences provided in SEQ ID NOs: 2-275, 394-397 and 488, is mutated to an A. In some embodiments, the D10 residue of the amino acid sequence provided in SEQ ID NO: 1, or a corresponding residue in any of the amino acid sequences provided in SEQ ID NOs: 2-275, 394-397 and 488, is a D.
A number of Cas9 sequences from various species were aligned to determine whether corresponding homologous amino acid residues of D10 and H840 of SEQ ID NO: 1 can be identified in other Cas9 proteins, allowing the generation of Cas9 variants with corresponding mutations of the homologous amino acid residues. The alignment was carried out using the NCBI Constraint-based Multiple Alignment Tool (COBALT (accessible at st-va.ncbi.nlm.nih.gov/tools/cobalt)), with the following parameters. Alignment parameters: Gap penalties −11, −1; End-Gap penalties −5, −1. CDD Parameters: Use RPS BLAST on; Blast E-value 0.003; Find Conserved columns and Recompute on. Query Clustering Parameters: Use query clusters on; Word Size 4; Max cluster distance 0.8; Alphabet Regular.
Examples of Cas9 and Cas9 equivalents are provided as follows; however, these specific examples are not meant to be limiting. The nucleobase editor fusions of the present disclosure may use any suitable napDNAbp, including any suitable Cas9 or Cas9 equivalent.
S. pyogenes Cas9 wild type
S. pyogenes dCas9 (D10A and H840A)
S. pyogenes Cas9 Nickase (D10A)
Streptococcus thermophilus CRISPR1 Cas9 (St1Cas9) Nickase (D9A)
Streptococcus thermophilus CRISPR3Cas9 (St3Cas9) Nickase (D10A)
S. aureus Cas9 wild type
S. aureus Cas9 Nickase (D10A)
Streptococcus thermophilus wild type CRISPR3 Cas9 (St3Cas9)
Streptococcus thermophilus CRISPR1 Cas9 wild type (St1Cas9)
Some aspects of the disclosure provide Cas9 domains that have different PAM specificities. Typically, Cas9 proteins, such as Cas9 from S. pyogenes (spCas9), require a canonical NGG PAM sequence to bind a particular nucleic acid region. This may limit the ability to edit desired bases within a genome. In some embodiments, the base editing fusion proteins provided herein may need to be placed at a precise location, for example where a target base is placed within a 4 base region (e.g., a “editing window”), which is approximately 15 bases upstream of the PAM. See Komor, A. C., et al., “Programmable editing of a target base in genomic DNA without double-stranded DNA cleavage” Nature 533, 420-424 (2016), the entire contents of which are hereby incorporated by reference. Accordingly, in some embodiments, any of the fusion proteins provided herein may contain a Cas9 domain that is capable of binding a nucleotide sequence that does not contain a canonical (e.g., NGG) PAM sequence. Cas9 domains that bind to non-canonical PAM sequences have been described in the art and would be apparent to the skilled artisan. For example, Cas9 domains that bind non-canonical PAM sequences have been described in Kleinstiver, B. P., et al., “Engineered CRISPR-Cas9 nucleases with altered PAM specificities” Nature 523, 481-485 (2015); and Kleinstiver, B. P., et al., “Broadening the targeting range of Staphylococcus aureus CRISPR-Cas9 by modifying PAM recognition” Nature Biotechnology 33, 1293-1298 (2015); the entire contents of each are hereby incorporated by reference.
For example, a napDNAbp domain with altered PAM specificity, such as a domain with at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% sequence identity with wild type Francisella novicida Cpf1 (SEQ ID NO: 16) (D917, E1006, and D1255), which has the following amino acid sequence:
RGERHLAYYTLVDGKGNIIKQDTFNIIGNDRMKTNYHDKLAAIEKDRDSARKDWKKINNIKE
DLNFGFKRGRFKVEKQVYQKLEKMLIEKLNYLVFKDNEFDK
ANGAYHIGLKGLMLLGRIKNNQEGKKLNLVIKNEEYFEFVQNRNN
Francisella novicida Cpf1 D917A
RGERHLAYYTLVDGKGNIIKQDTFNIIGNDRMKTNYHDKLAAIEKDRDSARKDWKKINNIKE
DLNFGFKRGRFKVEKQVYQKLEKMLIEKLNYLVFKDNEFDK
ANGAYHIGLKGLMLLGRIKNNQEGKKLNLVIKNEEYFEFVQNRNN
Francisella novicida Cpf1 E1006A
RGERHLAYYTLVDGKGNIIKQDTFNIIGNDRMKTNYHDKLAAIEKDRDSARKDWKKINNIKE
DLNFGFKRGRFKVEKQVYQKLEKMLIEKLNYLVFKDNEFDK
ANGAYHIGLKGLMLLGRIKNNQEGKKLNLVIKNEEYFEFVQNRNN
Francisella novicida Cpf1 D1255A
RGERHLAYYTLVDGKGNIIKQDTFNIIGNDRMKTNYHDKLAAIEKDRDSARKDWKKINNIKE
DLNFGFKRGRFKVEKQVYQKLEKMLIEKLNYLVFKDNEFDK
ANGAYHIGLKGLMLLGRIKNNQEGKKLNLVIKNEEYFEFVQNRNN
Francisella novicida Cpf1 D917A/E1006A
RGERHLAYYTLVDGKGNIIKQDTFNIIGNDRMKTNYHDKLAAIEKDRDSARKDWKKINNIKE
DLNFGFKRGRFKVEKQVYQKLEKMLIEKLNYLVFKDNEFDK
ANGAYHIGLKGLMLLGRIKNNQEGKKLNLVIKNEEYFEFVQNRNN
Francisella novicida Cpf1 D917A/D1255A
RGERHLAYYTLVDGKGNIIKQDTFNIIGNDRMKTNYHDKLAAIEKDRDSARKDWKKINNIKE
DLNFGFKRGRFKVEKQVYQKLEKMLIEKLNYLVFKDNEFDK
ANGAYHIGLKGLMLLGRIKNNQEGKKLNLVIKNEEYFEFVQNRNN
Francisella novicida Cpf1 E1006A/D1255A
RGERHLAYYTLVDGKGNIIKQDTFNIIGNDRMKTNYHDKLAAIEKDRDSARKDWKKINNIKE
DLNFGFKRGRFKVEKQVYQKLEKMLIEKLNYLVFKDNEFDK
ANGAYHIGLKGLMLLGRIKNNQEGKKLNLVIKNEEYFEFVQNRNN
Francisella novicida Cpf1 D917A/E1006A/D1255A
RGERHLAYYTLVDGKGNIIKQDTFNIIGNDRMKTNYHDKLAAIEKDRDSARKDWKKINNIKE
DLNFGFKRGRFKVEKQVYQKLEKMLIEKLNYLVFKDNEFDK
ANGAYHIGLKGLMLLGRIKNNQEGKKLNLVIKNEEYFEFVQNRNN
In some embodiments, the nucleic acid programmable DNA binding protein (napDNAbp) is a nucleic acid programmable DNA binding protein that does not require a canonical (NGG) PAM sequence. In some embodiments, the napDNAbp is an argonaute protein. One example of such a nucleic acid programmable DNA binding protein is an Argonaute protein from Natronobacterium gregoryi (NgAgo). NgAgo is an ssDNA-guided endonuclease. NgAgo binds 5′ phosphorylated ssDNA of ˜24 nucleotides (gDNA) to guide it to its target site and will make DNA double-strand breaks at the gDNA site. In contrast to Cas9, the NgAgo-gDNA system does not require a protospacer-adjacent motif (PAM). Using a nuclease inactive NgAgo (dNgAgo) can greatly expand the bases that may be targeted. The characterization and use of NgAgo have been described in Gao et al., Nat Biotechnol., 34(7): 768-73 (2016), PubMed PMID: 27136078; Swarts et al., Nature, 507(7491): 258-61 (2014); and Swarts et al., Nucleic Acids Res. 43(10) (2015): 5120-9, each of which is incorporated herein by reference. The sequence of Natronobacterium gregoryi Argonaute is provided in SEQ ID NO: 24.
The disclosed fusion proteins may comprise a napDNAbp domain having at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% sequence identity with wild type Natronobacterium gregoryi Argonaute (SEQ ID NO: 24), which has the following amino acid sequence:
acidoterrestris (strain ATCC 49025/DSM
shahii (strain DSM 19757/CCUG 47503/
S. canis (ScCas9)
In some embodiments, the base editors described herein can include any Cas9 equivalent. As used herein, the term “Cas9 equivalent” is a broad term that encompasses any napDNAbp protein that serves the same function as Cas9 in the present base editors despite that its amino acid primary sequence and/or its three-dimensional structure may be different and/or unrelated from an evolutionary standpoint. Thus, while Cas9 equivalents include any Cas9 ortholog, homolog, mutant, or variant described or embraced herein that are evolutionarily related, the Cas9 equivalents also embrace proteins that may have evolved through convergent evolution processes to have the same or similar function as Cas9, but which do not necessarily have any similarity with regard to amino acid sequence and/or three dimensional structure. The base editors described here embrace any Cas9 equivalent that would provide the same or similar function as Cas9 despite that the Cas9 equivalent may be based on a protein that arose through convergent evolution.
For example, CasX is a Cas9 equivalent that reportedly has the same function as Cas9 but which evolved through convergent evolution. Thus, the CasX protein described in Liu et al., “CasX enzymes comprises a distinct family of RNA-guided genome editors,” Nature, 2019, Vol. 566: 218-223, is contemplated to be used with the base editors described herein. In addition, any variant or modification of CasX is conceivable and within the scope of the present disclosure.
Cas9 is a bacterial enzyme that evolved in a wide variety of species. However, the Cas9 equivalents contemplated herein may also be obtained from archaea, which constitute a domain and kingdom of single-celled prokaryotic microbes different from bacteria.
In some embodiments, Cas9 equivalents may refer to CasX or CasY, which have been described in, for example, Burstein et al., “New CRISPR-Cas systems from uncultivated microbes.” Cell Res. 2017 Feb. 21. doi: 10.1038/cr.2017.21, the entire contents of which is hereby incorporated by reference. Using genome-resolved metagenomics, a number of CRISPR-Cas systems were identified, including the first reported Cas9 in the archaeal domain of life. This divergent Cas9 protein was found in little-studied nanoarchaea as part of an active CRISPR-Cas system. In bacteria, two previously unknown systems were discovered, CRISPR-CasX and CRISPR-CasY, which are among the most compact systems yet discovered. In some embodiments, Cas9 refers to CasX, or a variant of CasX. In some embodiments, Cas9 refers to a CasY, or a variant of CasY. It should be appreciated that other RNA-guided DNA binding proteins may be used as a nucleic acid programmable DNA binding protein (napDNAbp), and are within the scope of this disclosure. Also see Liu et al., “CasX enzymes comprises a distinct family of RNA-guided genome editors,” Nature, 2019, Vol. 566: 218-223. Any of these Cas9 equivalents are contemplated.
In some embodiments, the Cas9 equivalent comprises an amino acid sequence that is at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to a naturally-occurring CasX or CasY protein. In some embodiments, the napDNAbp is a naturally-occurring CasX or CasY protein. In some embodiments, the napDNAbp comprises an amino acid sequence that is at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to a wild-type Cas moiety or any Cas moiety provided herein.
In various embodiments, the nucleic acid programmable DNA binding proteins include, without limitation, Cas9 (e.g., dCas9 and nCas9), CasX, CasY, Cpf1, C2c1, C2c2, C2C3, Argonaute, Cas12a, and Cas12b. One example of a nucleic acid programmable DNA-binding protein that has different PAM specificity than Cas9 is Clustered Regularly Interspaced Short Palindromic Repeats from Prevotella and Francisella 1 (Cpf1). Similar to Cas9, Cpf1 is also a class 2 CRISPR effector. It has been shown that Cpf1 mediates robust DNA interference with features distinct from Cas9. Cpf1 is a single RNA-guided endonuclease lacking tracrRNA, and it utilizes a T-rich protospacer-adjacent motif (TTN, TTTN, or YTN). Moreover, Cpf1 cleaves DNA via a staggered DNA double-stranded break. Out of 16 Cpf1-family proteins, two enzymes from Acidaminococcus and Lachnospiraceae are shown to have efficient genome-editing activity in human cells. Cpf1 proteins are known in the art and have been described previously, for example Yamano et al., “Crystal structure of Cpf1 in complex with guide RNA and target DNA.” Cell (165) 2016, p. 949-962; the entire contents of which is hereby incorporated by reference. The state of the art may also now refer to Cpf1 enzymes as Cas12a.
In still other embodiments, the Cas protein may include any CRISPR associated protein, including but not limited to, Cas12a, Cas12b, Cas1, Cas1B, Cas2, Cas3, Cas4, Cas5, Cas6, Cas7, Cas8, Cas9 (also known as Csn1 and Csx12), Cas10, Csy1, Csy2, Csy3, Cse1, Cse2, Csc1, Csc2, Csa5, Csn2. Csm2, Csm3, Csm4, Csm5, Csm6, Cmr1, Cmr3, Cmr4, Cmr5, Cmr6, Csb1, Csb2, Csb3, Csx17, Csx14, Csx10, Csx16, CsaX, Csx3, Csx1, Csx15, Csf1, Csf2, Csf3, Csf4, homologs thereof, or modified versions thereof, and preferably comprising a nickase mutation (e.g., a mutation corresponding to the D10A mutation of the wild type Cas9 polypeptide of SEQ ID NO: 1).
In various other embodiments, the napDNAbp can be any of the following proteins: a Cas9, a Cpf1, a CasX, a CasY, a C2c1, a C2c2, a C2c3, a GeoCas9, a CjCas9, a Cas12a, a Cas12b, a Cas12g, a Cas12h, a Cas12i, a Cas13b, a Cas13c, a Cas13d, a Cas14, a Csn2, an xCas9, an SpCas9-NG, a circularly permuted Cas9, or an Argonaute (Ago) domain, or a variant thereof.
Exemplary Cas9 equivalent protein sequences can include the following:
Acidaminococcus sp.
Lachnospiraceae
bacterium
Prevotella
copri
Eubacterium
rectale
Clostridium sp.
Bacillus
hisashii
Thermomonas
hydrothermalis
Laceyella
sacchari
Dsulfonatronum
thiodismutans
The napDNAbp domains of the split nucleobase editors described herein may also comprise Cas12a/Cpf1 (dCpf1) variants that may be used as a guide nucleotide sequence-programmable DNA-binding protein domain. The Cas12a/Cpf1 protein has a RuvC-like endonuclease domain that is similar to the RuvC domain of Cas9 but does not have a HNH endonuclease domain, and the N-terminal of Cpf1 does not have the alfa-helical recognition lobe of Cas9. It was shown in Zetsche et al., Cell, 163, 759-771, 2015 (which is incorporated herein by reference) that, the RuvC-like domain of Cpf1 is responsible for cleaving both DNA strands and inactivation of the RuvC-like domain inactivates Cpf1 nuclease activity.
In some embodiments, the napDNAbp is a nucleic acid programmable DNA binding protein that does not require a canonical (NGG) PAM sequence. In some embodiments, the napDNAbp is an argonaute protein. In some embodiments, the disclosure provides napDNAbp domains that comprise SpCas9 variants that recognize and work best with NRRH, NRCH, and NRTH PAMs. See PCT Application No. PCT/US2019/47996, incorporated by reference herein. In some embodiments, the disclosed base editors comprise a napDNAbp domain selected from SpCas9-NRRH, SpCas9-NRTH, and SpCas9-NRCH.
In some embodiments, the disclosed base editors comprise a napDNAbp domain that has a sequence that is at least 90%, at least 95%, at least 98%, or at least 99% identical to SpCas9-NRRH. In some embodiments, the disclosed base editors comprise a napDNAbp domain that comprises SpCas9-NRRH. The SpCas9-NRRH has an amino acid sequence as presented in SEQ ID NO: 435 (underligned residues are mutated relative to SpCas9, as set forth in SEQ ID NO: 1)
In some embodiments, the disclosed base editors comprise a napDNAbp domain that has a sequence that is at least 90%, at least 95%, at least 98%, or at least 99% identical to SpCas9-NRCH. In some embodiments, the disclosed base editors comprise a napDNAbp domain that comprises SpCas9-NRCH. The SpCas9-NRCH has an amino acid sequence as presented in SEQ ID NO: 436 (underligned residues are mutated relative to SpCas9)
In some embodiments, the disclosed base editors comprise a napDNAbp domain that has a sequence that is at least 90%, at least 95%, at least 98%, or at least 99% identical to SpCas9-NRTH. In some embodiments, the disclosed base editors comprise a napDNAbp domain that comprises SpCas9-NRTH. The SpCas9-NRTH has an amino acid sequence as presented in SEQ ID NO: 437 (underligned residues are mutated relative to SpCas9)
The napDNAbp domains of the split nucleobase editors of the present disclosure may also comprise Cas9 variants with modified PAM specificities. Some aspects of this disclosure provide Cas9 proteins that exhibit activity on a target sequence that does not comprise the canonical PAM (5′-NGG-3′, where N is A, C, G, or T) at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5′-NGG-3′ PAM sequence at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5″-NNG-3″ PAM sequence at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5′-NNA-3′ PAM sequence at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5′-NNC-3′ PAM sequence at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5″-NNT-3″ PAM sequence at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5″-NGT-3″ PAM sequence at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5″-NGA-3″ PAM sequence at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5′-NGC-3′ PAM sequence at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5″-NAA-3″ PAM sequence at its 3″-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5″-NAC-3′ PAM sequence at its 3′-end. In some embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5″-NAT-3″ PAM sequence at its 3″-end. In still other embodiments, the Cas9 protein exhibits activity on a target sequence comprising a 5″-NAG-3′ PAM sequence at its 3″-end.
In some embodiments, the disclosed adenine base editors comprise a napDNAbp domain comprising a SpCas9-NG, which has a PAM that corresponds to NGN. In some embodiments, the disclosed base editors comprise a napDNAbp domain that has a sequence that is at least 90%, at least 95%, at least 98%, or at least 99% identical to SpCas9-NG. The sequence of SpCas9-NG is illustrated below:
In some embodiments, the disclosed base editors comprise a napDNAbp domain comprising a SaCas9-KKH, which has a PAM that corresponds to NNNRRT. In some embodiments, the disclosed base editors comprise a napDNAbp domain that has a sequence that is at least 90%, at least 95%, at least 98%, or at least 99% identical to SaCas9-KKH. The sequence of SaCas9-KKH is illustrated below:
S. aureus Cas9 nickase KKH (D10A/E782K/N968K/R1015H) (SaCas9-KKH)
In some embodiments, the disclosed adenine base editors comprise a napDNAbp domain comprising a xCas9, an evolved variant of SpCas9. In some embodiments, the disclosed base editors comprise a napDNAbp domain that has a sequence that is at least 90%, at least 95%, at least 98%, or at least 99% identical to xCas9. The sequence of xCas9 is illustrated below:
In various embodiments, the base editors disclosed herein may comprise a circular permutant of Cas9. The term “circularly permuted Cas9” or “circular permutant” of Cas9 or “CP-Cas9”) refers to any Cas9 protein, or variant thereof, that occurs or has been modify to engineered as a circular permutant variant, which means the N-terminus and the C-terminus of a Cas9 protein (e.g., a wild type Cas9 protein) have been topically rearranged. Such circularly permuted Cas9 proteins, or variants thereof, retain the ability to bind DNA when complexed with a guide RNA (gRNA). See, Oakes et al., “Protein Engineering of Cas9 for enhanced function,” Methods Enzymol, 2014, 546: 491-511 and Oakes et al., “CRISPR-Cas9 Circular Permutants as Programmable Scaffolds for Genome Modification,” Cell, Jan. 10, 2019, 176: 254-267, each of are incorporated herein by reference. The present disclosure contemplates any previously known CP-Cas9 or use a new CP-Cas9 so long as the resulting circularly permuted protein retains the ability to bind DNA when complexed with a guide RNA (gRNA).
In some embodiments, circular permutant Cas9 variants may be defined as a topological rearrangement of a Cas9 primary structure based on the following method, which is based on S. pyogenes Cas9 of SEQ ID NO: 1: (a) selecting a circular permutant (CP) site corresponding to an internal amino acid residue of the Cas9 primary structure, which dissects the original protein into an N-terminal portion and a C-terminal portion; (b) modifying the Cas9 protein sequence (e.g., by genetic engineering techniques) by moving the original C-terminal region (comprising the CP site amino acid) to preceed the original N-terminal region, thereby forming a new N-terminus of the Cas9 protein that now begins with the CP site amino acid residue. The CP site can be located in any domain of the Cas9 protein, including, for example, the helical-II domain, the RuvCIII domain, or the CTD domain. For example, the CP site may be located (relative the S. pyogenes Cas9 of SEQ ID NO: 1) at original amino acid residue 181, 199, 230, 270, 310, 1010, 1016, 1023, 1029, 1041, 1247, 1249, or 1282. Thus, once relocated to the N-terminus, original amino acid 181, 199, 230, 270, 310, 1010, 1016, 1023, 1029, 1041, 1247, 1249, or 1282 would become the new N-terminal amino acid. Nomenclature of these CP-Cas9 proteins may be referred to as Cas9-CP181, Cas9-CP199, Cas9-CP230, Cas9-CP270, Cas9-CP310, Cas9-CP1010, Cas9-CP1016, Cas9-CP1023, Cas9-CP1029, cas9-CP1041, Cas9-CP1247, Cas9-CP1249, and Cas9-CP1282, respectively. This description is not meant to be limited to making CP variants from SEQ ID NO: 1, but may be implemented to make CP variants in any Cas9 sequence, either at CP sites that correspond to these positions, or at other CP sites entirely. This description is not meant to limit the specific CP sites in any way. Virtually any CP site may be used to form a CP-Cas9 variant.
Exemplary CP-Cas9 amino acid sequences, based on the Cas9 of SEQ ID NO: 1, are provided below in which linker sequences are indicated by underlining and optional methionine (M) residues are indicated in bold. It should be appreciated that the disclosure provides CP-Cas9 sequences that do not include a linker sequence or that include different linker sequences. It should be appreciated that CP-Cas9 sequences may be based on Cas9 sequences other than that of SEQ ID NO: 1 and any examples provided herein are not meant to be limiting. Exemplary CP-Cas9 sequences are as follows:
SGGSGGSGGSGGSGGSGGDKKYSIGLAIGTNSVGWAVITDEYKVPSKKFKVLGNT
The Cas9 circular permutants that may be useful in the base editing constructs described herein. Exemplary C-terminal fragments of Cas9, based on the Cas9 of SEQ ID NO: 1, which may be rearranged to an N-terminus of Cas9, are provided below. It should be appreciated that such C-terminal fragments of Cas9 are exemplary and are not meant to be limiting. These exemplary CP-Cas9 fragments have the following sequences:
An exemplary alignment of four Cas9 sequences is provided below. The Cas9 sequences in the alignment are: Sequence 1 (S1): SEQ ID NO: 1|WP_010922251| gi 499224711|type II CRISPR RNA-guided endonuclease Cas9 [Streptococcus pyogenes]; Sequence 2 (S2): SEQ ID NO: 27|WP_039695303|gi 746743737|type II CRISPR RNA-guided endonuclease Cas9 [Streptococcus gallolyticus]; Sequence 3 (S3): SEQ ID NO: 28|WP_045635197|gi 782887988|type II CRISPR RNA-guided endonuclease Cas9 [Streptococcus mitis]; Sequence 4 (S4): SEQ ID NO: 29|5AXW_A|gi 924443546|Staphylococcus aureus Cas9. The HNH domain (bold and underlined) and the RuvC domain (boxed) are identified for each of the four sequences. Amino acid residues 10 and 840 in S1 and the homologous amino acids in the aligned sequences are identified with an asterisk following the respective amino acid residue.
KRIEEGIKELGSQIL-------KEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRLSD----YDVDH*IVPQSFLKDD
KKLQNSLKELGSNILNEEKPSYIEDKVENSHLQNDQLFLYYIQNGKDMYTGDELDIDHLSD----YDIDH*IIPQAFIKDD
KRIEDSLKILASGL---DSNILKENPTDNNQLQNDRLFLYYLQNGKDMYTGEALDINQLSS----YDIDH*IIPQAFIKDD
ERIEEIIRTTGK---------------ENAKYLIEKIKLHDMQEGKCLYSLEAIPLEDLLNNPFNYEVDH*IIPRSVSFDN
The alignment demonstrates that amino acid sequences and amino acid residues that are homologous to a reference Cas9 amino acid sequence or amino acid residue can be identified across Cas9 sequence variants, including, but not limited to Cas9 sequences from different species, by identifying the amino acid sequence or residue that aligns with the reference sequence or the reference residue using alignment programs and algorithms known in the art. This disclosure provides Cas9 variants in which one or more of the amino acid residues identified by an asterisk in SEQ ID NOs: 1 and 27-29 (e.g., 51, S2, S3, and S4, respectively) are mutated as described herein. The residues D10 and H840 in Cas9 of SEQ ID NO: 1 that correspond to the residues identified in SEQ ID NOs: 1 and 27-29 by an asterisk are referred to herein as “homologous” or “corresponding” residues. Such homologous residues can be identified by sequence alignment, e.g., as described above, and by identifying the sequence or residue that aligns with the reference sequence or residue. Similarly, mutations in Cas9 sequences that correspond to mutations identified in SEQ ID NO: 1 herein, e.g., mutations of residues 10, and 840 in SEQ ID NO: 1, are referred to herein as “homologous” or “corresponding” mutations. For example, the mutations corresponding to the D10A mutation in SEQ ID NO: 1 (51) for the four aligned sequences above are D11A for S2, D10A for S3, and D13A for S4; the corresponding mutations for H840A in SEQ ID NO: 1 (S1) are H850A for S2, H842A for S3, and H560A for S4.
A total of 250 Cas9 sequences (SEQ ID NOs: 1 and 27-275) from different species are provided. Amino acid residues corresponding to residues 10 and 840 of SEQ ID NO: 1 may be identified in the same manner as outlined above. All of these Cas9 sequences may be used in accordance with the present disclosure.
Nucleobase editors that convert a C to T, in some embodiments, comprise a cytosine deaminase. A “cytosine deaminase” refers to an enzyme that catalyzes the chemical reaction “cytosine+H2O→uracil+NH3” or “5-methyl-cytosine+H2O→thymine+NH3.” As it may be apparent from the reaction formula, such chemical reactions result in a C to U/T nucleobase change. In the context of a gene, such a nucleotide change, or mutation, may in turn lead to an amino acid change in the protein, which may affect the protein's function, e.g., loss-of-function or gain-of-function. In some embodiments, the C to T nucleobase editor comprises a dCas9 or nCas9 fused to a cytosine deaminase. In some embodiments, the cytosine deaminase domain is fused to the N-terminus of the dCas9 or nCas9.
Non-limiting examples of suitable cytosine deaminase domains are provided below, as SEQ ID NOs: 276-298 and 487.
Rhesus macaque APOBEC-3G
In some embodiments, a nucleobase editor converts an A to G. In some embodiments, the nucleobase editor comprises an adenosine deaminase. An “adenosine deaminase” is an enzyme involved in purine metabolism. It is needed for the breakdown of adenosine from food and for the turnover of nucleic acids in tissues. Its primary function in humans is the development and maintenance of the immune system. An adenosine deaminase catalyzes hydrolytic deamination of adenosine (forming inosine, which base pairs as G) in the context of DNA. There are no known adenosine deaminases that act on DNA. Instead, known adenosine deaminase enzymes only act on RNA (tRNA or mRNA). Evolved deoxyadenosine deaminase enzymes that accept DNA substrates and deaminate dA to deoxyinosine and here use in adenosine nucleobase editors have been described, e.g., in PCT Application PCT/US2017/045381, filed Aug. 3, 2017, which published as WO 2018/027078, PCT Application No. PCT/US2019/033848, which published as WO 2019/226953, PCT Application No PCT/US2019/033848, filed May 23, 2019, and PCT Application No. PCT/US2020/028568, filed Apr. 17, 2020; each of which is herein incorporated by reference by reference. Non-limiting examples of evolved adenosine deaminases that accept DNA as substrates are provided below.
Non-limiting examples evolved adenosine deaminases that accept DNA as substrates that are suitable for use as adenosine deaminase domains of the disclosed adenine nucleobase editors are provided below. In some embodiments, the adenosine deaminase domain of any of the disclosed nucleobase editors comprises an amino acid sequence having at least 85% identity, at least 90% identity, at least 95% identity, at least 98% identity, or at least 99% identity to an amino acid sequence comprising SEQ ID NO: 141, 314-321, 358, 407, 409-420, 422-424, 426-431, 433, 434, 438-457, 491-495, and 514.
In some embodiments, the adenosine deaminase domain of any of the disclosed nucleobase editors comprises an amino acid sequence having at least 85% identity, at least 90% identity, at least 95% identity, at least 98% identity, or at least 99% identity to an amino acid sequence comprising SEQ ID NO: 492 (TadA 7.10). In some embodiments, the adenosine deaminase domain of the disclosed nucleobase editors comprise an amino acid sequence comprising SEQ ID NO: 492.
In some embodiments, the adenosine deaminase domain of any of the disclosed nucleobase editors comprises an amino acid sequence having at least 85% identity, at least 90% identity, at least 95% identity, at least 98% identity, or at least 99% identity to an amino acid sequence comprising SEQ ID NO: 494 (TadA-8e). In some embodiments, the adenosine deaminase domain of the disclosed nucleobase editors comprise an amino acid sequence comprising SEQ ID NO: 494.
AEVEFSHEYWMRHALTLAKRAWDEREVPVGAVLVHNNRVIGEGWNRPFGRHDPTAHAEIMALRQGGLVM
NDLLSYFFRMRRQVFKAQKKAQSSTD
NDLLSYFFRMRRQVFKAQKKAQSSTD
NGLLSYFFRMRRQVFKAQKKAQSSTD
NALLSYFFRMRRQVFKAQKKAQSSTD
NDLLSYFFRMRRQVFKAQKKAQSSTD
NALLSYFFRMRRQVFKAQKKAQSSTD
NLLLSYFFRMRRQVFKAQKKAQSSTD
NALLSYFFRMRRQVFKAQKKAQSSTD
NALLSDFFRMRRQEIKAQKKAQSSTD
Staphylococcus aureus TadA:
Bacillus subtilis TadA:
Salmonella typhimurium (S. typhimurium) TadA:
Shewanella putrefaciens (S. putrefaciens)TadA:
Haemophilus influenzae F3031 (H. influenzae) TadA:
Caulobacter crescentus (C. crescentus) TadA:
Geobacter sulfurreducens (G. sulfurreducens) TadA:
Streptococcus pyogenes (S. pyogenes) TadA
In some embodiments, the adenosine deaminase domain comprises a E. coli TadA (SEQ ID NO: 314). Additional non-limiting examples of ecTadA deaminase mutants suitable for the adenine nucleobase editors of the disclosure are provided in Table 1. More specifically, the mutations in ecTadA and constructs expressing nucleobase editors comprising the modified ecTadA contemplated for use in the disclosed nucleobase editors are provided in Table 1.
S.aureusTadA-(SGGS)2-
S.aureusTadA-(SGGS)2-
S.aureusTadA-(SGGS)2-
S.aureusTadA-(SGGS)2-
S.aureusTadA-(SGGS)2-
S.aureusTadA-(SGGS)2-
In some embodiments, the adenosine deaminase comprises one or more of a W23X, H36X, N37X, P48X, I49X, R51X, N72X, L84X, S97X, A106X, D108X, H123X, G125X, A142X, S146X, D147X, R152X, E155X, I156X, K157X, and/or K161X mutation in SEQ ID NO: 314, or one or more corresponding mutations in another adenosine deaminase, where the presence of X indicates any amino acid other than the corresponding amino acid in the wild-type adenosine deaminase. In some embodiments, the adenosine deaminase comprises one or more of W23L, W23R, H36L, P48S, P48A, R51L, L84F, A106V, D108N, H123Y, A142N, S146C, D147Y, R152P, E155V, I156F, and/or K157N mutation in SEQ ID NO: 314, or one or more corresponding mutations in another adenosine deaminase.
In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, or twelve mutations selected from H36X, P48X, R51X, L84X, A106X, D108X, H123X, S146X, D147X, E155X, I156X, and K157X in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase, where X indicates the presence of any amino acid other than the corresponding amino acid in the wild-type adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, or twelve mutations selected from H36L, P48S, R51L, L84F, A106V, D108N, H123Y, S146C, D147Y, E155V, I156F, and K157N in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of a H36L, P48S, R51L, L84F, A106V, D108N, H123Y, S146C, D147Y, E155V, I156F, and K157N mutation in SEQ ID NO: 314, or corresponding mutations in another adenosine deaminase.
In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, or thirteen mutations selected from H36X, P48X, R51X, L84X, A106X, D108X, H123X, A142X, S146X, D147X, E155X, I156X, and K157X in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase, where X indicates the presence of any amino acid other than the corresponding amino acid in the wild-type adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, or thirteen mutations selected from H36L, P48S, R51L, L84F, A106V, D108N, H123Y, A142N, S146C, D147Y, E155V, I156F, and K157N in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of a H36L, P48S, R51L, L84F, A106V, D108N, H123Y, A142N, S146C, D147Y, E155V, I156F, and K157N mutation in SEQ ID NO: 314, or corresponding mutations in another adenosine deaminase.
In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, or fourteen mutations selected from W23X, H36X, P48X, R51X, L84X, A106X, D108X, H123X, A142X, S146X, D147X, E155X, I156X, and K157X in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase, where X indicates the presence of any amino acid other than the corresponding amino acid in the wild-type adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, or fourteen mutations selected from W23L, H36L, P48A, R51L, L84F, A106V, D108N, H123Y, A142N, S146C, D147Y, E155V, I156F, and K157N in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of a W23L, H36L, P48A, R51L, L84F, A106V, D108N, H123Y, A142N, S146C, D147Y, E155V, I156F, and K157N mutation in SEQ ID NO: 314, or corresponding mutations in another adenosine deaminase.
In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, or fifteen mutations selected from W23X, H36X, P48X, R51X, L84X, A106X, D108X, H123X, A142X, S146X, D147X, R152X, E155X, I156X, and K157X in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase, where X indicates the presence of any amino acid other than the corresponding amino acid in the wild-type adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, or fifteen mutations selected from W23L, H36L, P48A, R51L, L84F, A106V, D108N, H123Y, A142N, S146C, D147Y, R152P, E155V, I156F, and K157N in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of a W23L, H36L, P48A, R51L, L84F, A106V, D108N, H123Y, A142N, S146C, D147Y, R152P, E155V, I156F, and K157N mutation in SEQ ID NO: 314, or corresponding mutations in another adenosine deaminase.
In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, or fourteen mutations selected from W23X, H36X, P48X, R51X, L84X, A106X, D108X, H123X, S146X, D147X, R152X, E155X, I156X, and K157X in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase, where X indicates the presence of any amino acid other than the corresponding amino acid in the wild-type adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, or fourteen mutations selected from W23R, H36L, P48A, R51L, L84F, A106V, D108N, H123Y, S146C, D147Y, R152P, E155V, I156F, and K157N in SEQ ID NO: 314, or a corresponding mutation or mutations in another adenosine deaminase. In some embodiments, the adenosine deaminase comprises or consists of a W23R, H36L, P48A, R51L, L84F, A106V, D108N, H123Y, S146C, D147Y, R152P, E155V, I156F, and K157N mutation in SEQ ID NO: 314, or corresponding mutations in another adenosine deaminase.
Nucleobase Editors
In some aspects, split nucleobase editors may be used in the present disclosure. Some aspects of the present disclosure relate to compositions comprising (i) a first nucleotide sequence encoding an N-terminal portion of a nucleobase editor fused at its C-terminus to an intein-N; and (ii) a second nucleotide sequence encoding an intein-C fused to the N-terminus of a C-terminal portion of the nucleobase editor.
Nucleobase editor variants are contemplated. For example, a nucleobase editor variant may also be “split” as described herein. The split nucleobase editors may comprise an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the nucleobase editor sequences (SEQ ID NOs: 303-313, 362, 364, 365, 369-372, 399-406, 482, 489-490, 515-518, 550-552, and NOs: 323-342, 379-383, 385-388, 458-478, 480, 483, and 553) provided herein.
In some embodiments, the N-terminal portion of a split nucleobase editor comprises an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to the corresponding N-terminal portion of any one of the nucleobase editors provided herein (e.g., a nucleobase editor comprising an N-terminal amino acid sequence of any one of SEQ ID NOs: 303-313, 362, 364, 365, 369-372, 399-406, 482, 489-490, 515-518, 550-552, and SEQ ID NOs: 323-342, 379-383, 385-388, 458-478, 480, 483, and 553). In some embodiments, the N-terminal portion of the split nucleobase editor comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 30%, no more than 25%, no more than 20%, no more than 15%, no more than 10%, no more than 5%, no more than 1% longer or shorter) than the corresponding portion of any of the nucleobase editors provided herein. In some embodiments, the N-terminal portion of the split nucleobase editor comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 200 amino acids, no more than 150 amino acids, no more than 100 amino acids, no more than 50 amino acids, no more than 10 amino acids, no more than 5 amino acids, or no more than 2 amino acids longer or shorter) than the corresponding portion of any of the nucleobase editors provided herein.
In some embodiments, the C-terminal portion of a split nucleobase editor comprises an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to the corresponding C-terminal portion of any one of the nucleobase editors provided herein (e.g., a nucleobase editor comprising a C-terminal amino acid sequence of any one of SEQ ID NOs: 303-313, 362, 364, 365, 369-372, 399-406, 482, 489-490, 515-518, 550-552, or SEQ ID NOs: 323-342, 379-383, 385-388, 458-478, 480, 483, and 553). In some embodiments, the C-terminal portion of the split nucleobase editor comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 30%, no more than 25%, no more than 20%, no more than 15%, no more than 10%, no more than 5%, no more than 1% longer or shorter) than the corresponding portion of any of the nucleobase editors provided herein. In some embodiments, the C-terminal portion of the split nucleobase editor comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 200 amino acids, no more than 150 amino acids, no more than 100 amino acids, no more than 50 amino acids, no more than 10 amino acids, no more than 5 amino acids, or no more than 2 amino acids longer or shorter) than the corresponding portion of any of the nucleobase editors provided herein.
Exemplary adenine and cytidine nucleobase editors are described in Rees & Liu, Base editing: precision chemistry on the genome and transcriptome of living cells, Nat. Rev. Genet. 2018; 19(12):770-788; as well as U.S. Patent Publication No. 2018/0073012, published Mar. 15, 2018, which issued as U.S. Pat. No. 10,113,163, on Oct. 30, 2018; U.S. Patent Publication No. 2017/0121693, published May 4, 2017, which issued as U.S. Pat. No. 10,167,457 on Jan. 1, 2019; PCT Publication No. WO 2017/070633, published Apr. 27, 2017; U.S. Patent Publication No. 2015/0166980, published Jun. 18, 2015; U.S. Pat. No. 9,840,699, issued Dec. 12, 2017; and U.S. Pat. No. 10,077,453, issued Sep. 18, 2018, the contents of each of which are incorporated herein by reference in their entireties.
Non-limiting, exemplary types of nucleobase editors (including C to T, A to G, and C to G nucleobase editors) and their respective sequences are provided below. In some embodiments, the nucleobase editor is a variant of the nucleobase editors described herein. For example, in some embodiments, the nucleobase editor is at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75% at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to a nucleobase editor described herein (exemplary sequences are provided below). In some embodiments, the nucleobase editor comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 30%, no more than 25%, no more than 20%, no more than 15%, no more than 10%, no more than 5%, no more than 1% longer or shorter) than any of the nucleobase editors provided herein. In some embodiments, the nucleobase editor comprises an amino acid sequence that is shorter or longer in length (e.g., by no more than 500 amino acids, no more than 450 amino acids, no more than 400 amino acids, no more than 350 amino acids, no more than 300 amino acids, no more than 250 amino acids, no more than 200 amino acids, no more than 200 amino acids, no more than 150 amino acids, no more than 100 amino acids, no more than 50 amino acids, no more than 10 amino acids, no more than 5 amino acids longer or shorter) than any of the nucleobase editors provided herein.
In some aspects, the methods of the present disclosure provides cytidine nucleobase editors (CBEs) comprising a napDNAbp domain and a cytosine deaminase domain that enzymatically deaminates a cytosine nucleobase of a C:G nucleobase pair to a uracil. The uracil may be subsequently converted to a thymine (T) by the cell's DNA repair and replication machinery. The mismatched guanine (G) on the opposite strand may subsequently be converted to an adenine (A) by the cell's DNA repair and replication machinery. In this manner, a target C:G nucleobase pair is ultimately converted to a T:A nucleobase pair.
In some aspects, the base editing methods of the disclosure comprise the use of a cytidine nucleobase editor. Exemplary cytidine nucleobase editors include, but are not limited to, BE3, BE3.9max, BE4max, BE4-SaKKH, BE3.9-NG, BE3.9-NRRH, or BE4max-VRQR. In certain embodiments, the cytidine nucleobase editor used in the disclosed methods is a BE4max, BE4-SaKKH, BE4max-VQR, or BE4max-VRQR. Other CBEs may be used to deaminate a C nucleobase in accordance with the disclosed methods.
In some aspects, the disclosure provides complexes of nucleobase editors and guide RNAs that comprise a CBE. Exemplary cytidine nucleobase editors of the disclosed complexes include, but are not limited to, BE3, BE3.9max, BE4max, BE4-SaKKH, BE3.9-NG, BE3.9-NRRH, BE4max-VQR, or BE4max-VRQR. In certain embodiments, the cytidine nucleobase editor used in the disclosed complexes is a BE4max, BE4-SaKKH, BE4max-VQR, or BE4max-VRQR. Other CBEs may be used to deaminate a C nucleobase in accordance with the disclosed complexes.
Exemplary complexes of CBEs may provide an off-target editing frequency of less than 2.0% after being contacted with a nucleic acid molecule comprising a target sequence, e.g., a target nucleobase pair. Further exemplary CBE complexes provide an off-target editing frequency of less than 1.5% after being contacted with a nucleic acid molecule comprising a target sequence comprising a target nucleobase pair. Further exemplary CBE complexes may provide an off-target editing frequency of less than 1.25%, less than 1.1%, less than 1%, less than 0.75%, less than 0.5%, less than 0.4%, less than 0.25%, less than 0.2%, less than 0.15%, less than 0.1%, less than 0.05%, or less than 0.025%, after being contacted with a nucleic acid molecule comprising a target sequence.
For instance, the cytidine nucleobase editors YE1-BE4, YE1-CP1028, YE1-SpCas9-NG (also referred to herein as YE1-NG), R33A-BE4, and R33A+K34A-BE4-CP1028, which are described below, may exhibit off-target editing frequencies of less than 0.75% (e.g., about 0.4% or less) while maintaining on-target editing efficiencies of about 60% or more, in target sequences in mammalian cells. Each of these nucleobase editors comprises modified cytosine deaminases (e.g., YE1, R33A, or R33A+K34A) and may further comprise a Cas9 domain with an expanded PAM window (e.g., SpCas9-NG or circularly permuted Cas9 domains, e.g., CP1028). These five nucleobase editors may be the most preferred for applications in which off-target editing, and in particular Cas9-independent off-target editing, must be minimized. In particular, nucleobase editors comprising a YE1 deaminase domain provide efficient on-target editing with greatly decreased Cas9-independent editing, as confirmed by whole-genome sequencing.
Exemplary CBEs may further possess an on-target editing efficiency of more than 50% after being contacted with a nucleic acid molecule comprising a target sequence. Further exemplary CBEs possess an on-target editing efficiency of more than 60% after being contacted with a nucleic acid molecule comprising a target sequence. Further exemplary CBEs possess an on-target editing efficiency of more than 65%, more than 70%, more than 75%, more than 80%, more than 82.5%, or more than 85% after being contacted with a nucleic acid molecule comprising a target sequence. The disclosed CBEs may exhibit indel frequencies of less than 0.75%, less than 0.6%, less than 0.5%, less than 0.4%, less than 0.3%, or less than 0.2% after being contacted with a nucleic acid molecule containing a target sequence.
The disclosed CBEs may further comprise one or more nuclear localization signals (NLSs) and/or two or more uracil glycosylase inhibitor (UGI) domains. Thus, the nucleobase editors may comprise the structure: NH2-[first nuclear localization sequence]-[cytosine deaminase domain]-[napDNAbp domain]-[first UGI domain]-[second UGI domain]-[second nuclear localization sequence]-COOH, wherein each instance of “]-[” indicates the presence of an optional linker sequence. Exemplary CBEs may have a structure that comprises the “BE4max” architecture, with an NH2-[NLS]-[cytosine deaminase]-[Cas9 nickase]-[UGI domain]-[UGI domain]-[NLS]-COOH structure, having optimized nuclear localization signals and wherein the napDNAbp domain comprises a Cas9 nickase. This BE4max structure was reported to have optimized codon usage for expression in human cells, as reported in Koblan et al., Nat Biotechnol. 2018; 36(9):843-846, herein incorporated by reference.
In other embodiments, exemplary CBEs may have a structure that comprises a modified BE4max architecture that contains a napDNAbp domain comprising a Cas9 variant other than Cas9 nickase, such as SpCas9-NG, xCas9, or circular permutant CP1028. Accordingly, exemplary CBEs may comprise the structure: NH2-[NLS]-[cytosine deaminase]-[xCas9]-[UGI domain]-[UGI domain]-[NLS]-COOH; or NH2-[NLS]-[cytosine deaminase]-[SpCas9-NG]-[UGI domain]-[UGI domain]-[NLS]-COOH, wherein each instance of “]-[” indicates the presence of an optional linker sequence.
The disclosed CBEs may comprise modified (or evolved) cytosine deaminase domains, such as deaminase domains that recognize an expanded PAM sequence, have improved efficiency of deaminating 5′-GC targets, and/or make edits in a narrower target window, In some embodiments, the disclosed cytidine nucleobase editors comprise evolved nucleic acid programmable DNA binding proteins (napDNAbp), such as an evolved Cas9.
Exemplary cytidine nucleobase editors comprise amino acid sequences that are at least least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.5% identical to any one of the amino acid sequences SEQ ID NOs: 362, 365, 370-372, 399, 482, 489, 490, and 515-518. In particular embodiments, the disclosed cytidine nucleobase editors comprise an amino acid sequence that is at least 90% identical to any one of SEQ ID NOs: 365, 372, 399, 482, and 490. In particular embodiments, the disclosed cytidine nucleobase editors comprise the amino acid sequence of any one of SEQ ID NOs: 365, 372, 399, 482, and 490.
Where indicated, “BE4-” and “—BE4” refer to the BE4max architecture, or NH2-[first nuclear localization sequence]-[cytosine deaminase domain]-[32aa linker]-[SpCas9 nickase (nCas9, or nSpCas9) domain]-[9aa linker]-[first UGI domain]-[9aa-linker]-[second UGI domain]-[second nuclear localization sequence]-COOH. Where indicated, “BE4max, modified with SpCas9-NG” and “—SpCas9-NG” refer to a modified BE4max architecture in which the SpCas9 nickase domain has been replaced with an SpCas9-NG, i.e., NH2-[first nuclear localization sequence]-[cytosine deaminase domain]-[32aa linker]-[SpCas9-NG]-[9aa linker]-[first UGI domain]-[9aa-linker]-[second UGI domain]-[second nuclear localization sequence]-COOH.
As discussed above, preferred nucleobase editors comprise modified cytosine deaminases (e.g., YE1, R33A, or R33A+K34A) and may further comprise a modified napDNAbp domain such as a Cas9 domain with an expanded PAM window (e.g., SpCas9-NG). For the purposes of clarity, the cytosine deaminase domain in some of the following amino acid sequences may be indicated in Bold, and the napDNAbp domains may be indicated in underline.
Non-limiting examples of C to T nucleobase editors are provided below, as SEQ ID NOs: 303-313, 362, 364, 365, 367, 369-372, 399-406, 482, 489-490, 515-518, and 550-552.
DVIDAGVRLFKEANVENNEGRRSKRGARRLKRRRRHRIQRVKKLLFDYNLLTDHSELSGINPYEA
RVKGLSQKLSEEEFSAALLHLAKRRGVHNVNEVEEDTGNELSTKEQISRNSKALEEKYVAELQLE
RLKKDGEVRGSINRFKTSDYVKEAKQLLKVQKAYHQLDQSFIDTYIDLLETRRTYYEGPGEGSPFG
WKDIKEWYEMLMGHCTYFPEELRSVKYAYNADLYNALNDLNNLVITRDENEKLEYYEKFQIIEN
VFKQKKKPTLKQIAKEILVNEEDIKGYRVTSTGKPEFTNLKVYHDIKDITARKEIIENAELLDQIAKI
LTIYQSSEDIQEELTNLNSELTQEEIEQISNLKGYTGTHNLSLKAINLILDELWHTNDNQIAIFNRLKL
VPKKVDLSQQKEIPTTLVDDFILSPVVKRSFIQSIKVINAIIKKYGLPNDIIIELAREKNSKDAQKMIN
EMQKRNRQTNERIEEIIRTTGKENAKYLIEKIKLHDMQEGKCLYSLEAIPLEDLLNNPFNYEVDHIIP
RSVSFDNSFNNKVLVKQEEASKKGNRTPFQYLSSSDSKISYETFKKHILNLAKGKGRISKTKKEYLL
EERDINRFSVQKDFINRNLVDTRYATRGLMNLLRSYFRVNNLDVKVKSINGGFTSFLRRKWKFKK
ERNKGYKHHAEDALIIANADFIFKEWKKLDKAKKVMENQMFEEKQAESMPEIETEQEYKEIFITPH
QIKHIKDFKDYKYSHRVDKKPNRELINDTLYSTRKDDKGNTLIVNNLNGLYDKDNDKLKKLINKS
PEKLLMYHHDPQTYQKLKLIMEQYGDEKNPLYKYYEETGNYLTKYSKKDNGPVIKKIKYYGNKL
NAHLDITDDYPNSRNKVVKLSLKPYRFDVYLDNGVYKFVTVKNLDVIKKENYYEVNSKCYEEAK
KLKKISNQAEFIASFYNNDLIKINGELYRVIGVNNDLLNRIEVNMIDITYREYLENMNDKRPPRIIKTI
ASKTQSIKKYSTDILGNLYEVKSKKHPQIIKKGSGGSTNLSDIIEKETGKQLVIQESILMLPEEVEEVI
DVIDAGVRLFKEANVENNEGRRSKRGARRLKRRRRHRIQRVKKLLFDYNLLTDHSELSGINPYEA
RVKGLSQKLSEEEFSAALLHLAKRRGVHNVNEVEEDTGNELSTKEQISRNSKALEEKYVAELQLE
RLKKDGEVRGSINRFKTSDYVKEAKQLLKVQKAYHQLDQSFIDTYIDLLETRRTYYEGPGEGSPFG
WKDIKEWYEMLMGHCTYFPEELRSVKYAYNADLYNALNDLNNLVITRDENEKLEYYEKFQIIEN
VFKQKKKPTLKQIAKEILVNEEDIKGYRVTSTGKPEFTNLKVYHDIKDITARKEIIENAELLDQIAKI
LTIYQSSEDIQEELTNLNSELTQEEIEQISNLKGYTGTHNLSLKAINLILDELWHTNDNQIAIFNRLKL
VPKKVDLSQQKEIPTTLVDDFILSPVVKRSFIQSIKVINAIIKKYGLPNDIIIELAREKNSKDAQKMIN
EMQKRNRQTNERIEEIIRTTGKENAKYLIEKIKLHDMQEGKCLYSLEAIPLEDLLNNPFNYEVDHIIP
RSVSFDNSFNNKVLVKQEEASKKGNRTPFQYLSSSDSKISYETFKKHILNLAKGKGRISKTKKEYLL
EERDINRFSVQKDFINRNLVDTRYATRGLMNLLRSYFRVNNLDVKVKSINGGFTSFLRRKWKFKK
ERNKGYKHHAEDALIIANADFIFKEWKKLDKAKKVMENQMFEEKQAESMPEIETEQEYKEIFITPH
QIKHIKDFKDYKYSHRVDKKPNRKLINDTLYSTRKDDKGNTLIVNNLNGLYDKDNDKLKKLINKS
PEKLLMYHHDPQTYQKLKLIMEQYGDEKNPLYKYYEETGNYLTKYSKKDNGPVIKKIKYYGNKL
NAHLDITDDYPNSRNKVVKLSLKPYRFDVYLDNGVYKFVTVKNLDVIKKENYYEVNSKCYEEAK
KLKKISNQAEFIASFYKNDLIKINGELYRVIGVNNDLLNRIEVNMIDITYREYLENMNDKRPPHIIKTI
ASKTQSIKKYSTDILGNLYEVKSKKHPQIIKKGSGGSTNLSDIIEKETGKQLVIQESILMLPEEVEEVI
TSHKIWRHSSKNTTKHVEVNFIEKFTSERHFCPSTSCSITWFLSWSPCGECSKAITEFLSQHPN
VTLVIYVARLYHHMDQQNRQGLRDLVNSGVTIQIMTAPEYDYCWRNFVNYPPGKEAHWPR
YPPLWMKLYALELHAGILGLPPCLNILRRKQPQLTFFTIALQSCHYQRLPPHILWATGLKSG
RLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEKY
PTIYHLRKKLVDSTDICADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPINA
SGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDDD
LDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLPE
KYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNGSIPHQIH
LGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEVVDKGA
SAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDLLFKTN
RKVTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTLFE
DREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFMQL
IHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPENIVIEMARE
NQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRLSD
YDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTKAE
RGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQFYK
VREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIMN
FFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESILPKRN
SDKLIARKKDWDPKKYGGFDSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDFLEAK
GYKEVKKDLIIKLPKYSLFELENGRKRMLASAGELQKGNELALPSKYVNFLYLASHYEKLKGSPEDNEQK
QLFVEQHKHYLDETIEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGAPAAFKYF
DTTIDRKRYTSTKEVLDATLIHQSITGLYETRIDLSQLGGDSGGSGGSGGSTNLSDIIEKETGKQLVIQES
RLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEKY
PTIYHLRKKLVDSTDICADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPINA
SGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDDD
LDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLPE
KYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNGSIPHQIH
LGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEVVDKGA
SAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDLLFKTN
RKVTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTLFE
DREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFMQL
IHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPENIVIEMARE
NQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRLSD
YDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTKAE
RGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQFYK
VREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIMN
FFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRICVLSMPQVNIVKKTEVQTGGFSKESILPKRN
SDKLIARKKDWDPKKYGGFDSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDFLEAK
GYKEVKKDLIIKLPKYSLFELENGRKRMLASAGELQKGNELALPSKYVNFLYLASHYEKLKGSPEDNEQK
QLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGAPAAFKYF
DTTIDRKRYTSTKEVLDATLIHQSITGLYETRIDLSQLGGDSGGSGGSGGSTNLSDIIEKETGKQLVIQES
RLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEKY
PTIYHLRKKLVDSTDICADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPINA
SGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDDD
LDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLPE
KYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNGSIPHQIH
LGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEVVDKGA
SAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDLLFKTN
RKVTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTLFE
DREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFMQL
IHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPENIVIEMARE
NQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRLSD
YDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTKAE
RGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQFYK
VREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIMN
FFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESILPKRN
SDKLIARKKDWDPKKYGGFDSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDFLEAK
GYKEVKKDLIIKLPKYSLFELENGRKRMLASAGELQKGNELALPSKYVNFLYLASHYEKLKGSPEDNEQK
QLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGAPAAFKYF
DTTIDRKRYTSTKEVLDATLIHQSITGLYETRIDLSQLGGDSGGSGGSGGSTNLSDIIEKETGKQLVIQES
TRLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEK
YPTIYHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPIN
ASGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDD
DLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLP
EKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNGSIPHQI
HLGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEVVDK
GASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDLLFK
TNRINTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTL
FEDREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFM
QLIHDDSLTFKEDIQICAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPENIVIEMA
RENQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRL
SDYDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTK
AERGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQF
YKVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIM
NFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESILPKR
NSDKLIARKKDWDPKKYGGFDSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDFLEA
KGYKEVKKDLIIKLPKYSLFELENGRKRMLASAGELQKGNELALPSKYVNFLYLASHYEKLKGSPEDNEQ
KQLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGAPAAFKY
FDTTIDRKRYTSTKEVLDATLIHQSITGLYETRIDLSQLGGDSGGSGGSGGSTNLSDIIEKETGKQLVIQE
TRLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEK
YPTIYHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPIN
ASGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDD
DLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLP
EKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNGSIPHQI
HLGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEVVDK
GASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDLLFK
TNRINTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTL
FEDREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFM
QLIHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPENIVIEMA
RENQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRL
SDYDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTK
AERGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQF
YKVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIM
NFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESILPKR
NSDKLIARKKDWDPKKYGGFDSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDFLEA
KGYKEVKKDLIIKLPKYSLFELENGRKRMLASAGELQKGNELALPSKYVNFLYLASHYEKLKGSPEDNEQ
KQLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGAPAAFKY
TRLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEK
YPTIYHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPIN
ASGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDD
DLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLP
EKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNGSIPHQI
HLGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEVVDK
GASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDLLFK
TNRINTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTL
FEDREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFM
QLIHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPENIVIEMA
RENQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRL
SDYDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTK
AERGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQF
YKVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIM
NFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESILPKR
NSDKLIARKKDWDPKKYGGFDSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDFLEA
KGYKEVKKDLIIKLPKYSLFELENGRKRMLASAGELQKGNELALPSKYVNFLYLASHYEKLKGSPEDNEQ
KQLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGAPAAFKY
FDTTIDRKRYTSTKEVLDATLIHQSITGLYETRIDLSQLGGDSGGSGGSGGSTNLSDIIEKETGKQLVIQE
SGETAEATRLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDE
VAYHEKYPTIYHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQL
FEENPINASGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLS
KDTYDDDLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKAL
VRQQLPEKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDN
GSIPHQIHLGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNF
EEVVDKGASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAI
VDLLFKTNRKVTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDI
VLTLTLFEDREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFA
NRNFMQLIHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPEN
IVIEMARENQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQE
LDINRLSDYDVDHIVPQSFLKDDSIDNICVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRK
FDNLTKAERGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFR
KDFQFYKVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYF
FYSNIMNFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSK
ESILPKRNSDKLIARKKDWDPKKYGGFDSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNP
IDFLEAKGYKEVKKDLIIKLPKYSLFELENGRKRMLASAGELQKGNELALPSKYVNFLYLASHYEKLKGSP
EDNEQKQLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGA
PAAFKYFDTTIDRKRYTSTKEVLDATLIHQSITGLYETRIDLSQLGGDSGGSGGSGGSTNLSDIIEKETGK
TRLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEK
YPTIYHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPIN
ASGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDD
DLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLP
EKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNGSIPHQI
HLGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEVVDK
GASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDLLFK
TNRKVTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTL
FEDREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFM
QLIHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPENIVIEMA
RENQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRL
SDYDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTK
AERGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQF
YKVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIM
NFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESILPKR
NSDKLIARKKDWDPKKYGGFDSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDFLEA
KGYKEVKKDLIIKLPKYSLFELENGRKRMLASAGELQKGNELALPSKYVNFLYLASHYEKLKGSPEDNEQ
KQLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGAPAAFKY
FDTTIDRKRYTSTKEVLDATLIHQSITGLYETRIDLSQLGGDSGGSGGSGGSTNLSDIIEKETGKQLVIQE
TRLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEK
YPTIYHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPIN
DLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLP
EKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNGSIPHQI
HLGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEVVDK
GASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDLLFK
TNRKVTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTL
FEDREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFM
QLIHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPENIVIEMA
RENQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRL
SDYDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTK
AERGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQF
YKVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIM
NFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESIRPKR
NSDKLIARKKDWDPKKYGGFVSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDFLEAK
GYKEVKKDLIIKLPKYSLFELENGRKRMLASARFLQKGNELALPSKYVNFLYLASHYEKLKGSPEDNEQK
QLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGAPRAFKYF
DTTIDRKVYRSTKEVLDATLIHQSITGLYETRIDLSQLGGDSGGSGGSGGSTNLSDIIEKETGKQLVIQES
RHRIQRVKKLLFDYNLLTDHSELSGINPYEARVKGLSQKLSEEEFSAALLHLAKRRGVHNVNEVEEDTGN
ELSTKEQISRNSKALEEKYVAELQLERLKKDGEVRGSINRFKTSDYVKEAKQLLKVQKAYHQLDQSFIDTY
IDLLETRRTYYEGPGEGSPFGWKDIKEWYEMLMGHCTYFPEELRSVKYAYNADLYNALNDLNNLVITRD
ENEKLEYYEKFQIIENVFKQKKKPTLKQIAKEILVNEEDIKGYRVTSTGKPEFTNLKVYHDIKDITARKEII
ENAELLDQIAKILTIYQSSEDIQEELTNLNSELTQEEIEQISNLKGYTGTHNLSLKAINLILDELWHTNDNQI
AIFNRLKLVPKKVDLSQQKEIPTTLVDDFILSPVVKRSFIQSIKVINAIIKKYGLPNDIIIELAREKNSKDAQK
MINEMQKRNRQTNERIEEHRITGKENAKYLIEKIKLHDMQEGKCLYSLEAIPLEDLLNNPFNYEVDHIIP
RSVSFDNSFNNKVLVKQEENSKKGNRTPFQYLSSSDSKISYETFKKHILNLAKGKGRISKTKKEYLLEERDI
NRFSVQKDFINRNLVDTRYATRGLMNLLRSYFRVNNLDVKVKSINGGFTSFLRRKWKFKKERNKGYKHH
AEDALHANADFIFKEWKKLDKAKKVMENQMFEEKQAESMPEIETEQEYKEIFITPHQIKHIKDFKDYKY
SHRVDKKPNRKLINDTLYSTRKDDKGNTLIVNNLNGLYDKDNDKLKKLINKSPEKLLMYHHDPQTYQKL
KLIMEQYGDEKNPLYKYYEETGNYLTKYSKKDNGPVIKKIKYYGNKLNAHLDITDDYPNSRNKVVKLSLK
PYRFDVYLDNGVYKFVTVKNLDVIKKENYYEVNSKCYEEAKKLKKISNQAEFIASFYKNDLIKINGELYRVI
GVNNDLLNRIEVNMIDITYREYLENMNDKRPPHIIKTIASKTQSIKKYSTDILGNLYEVKSKKHPQIIKKGS
GGSGGSGGSTNLSDHEKETGKQLVIQESILMLPEEVEEVIGNKPESDILVHTAYDESTDENVMLLTSDAP
EYKPWALVIQDSNGENKIKMLSGGSGGSGGSTNLSDHEKETGKQLVIQESILMLPEEVEEVIGNKPESDI
LVHTAYDESTDENVMLLTSDAPEYKPWALVIQDSNGENKIKMLSGGSKRTADGSEFEPKKKRKV
TRLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEK
YPTIYHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPIN
ASGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDD
DLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMVKRYDEHHQDLTLLKALVRQQLP
EKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLISKQRTFDNGIIPHQI
HLGELHAILRRQGDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEVVDK
GASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDLLFK
TNRKVTV
K
QLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTL
FEDREMIEERLKTYAHLFDDKVMKQLKRLRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFM
QLIHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGGHKPENIVIEMA
RENQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRL
SDYDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTK
AERGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQF
YKVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIM
NFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESILPKG
NSDKLIARKKDWDPKKYGGFNSPTAAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIGFLEA
KGYKEVKKDLIIKLPKYSLFELENGRKRMLASAGVLHKGNELALPSKYVNFLYLASHYEKLKGSPEDNEQ
KQLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGVPAAFKY
FDTTIDKKRYTSTKEVLDATLIHQSITGLYETRIDLSQLGGDS
GGSGGSGGSTNLSDITEKETGKQLVIQE
NWGGRHSIWRHTSQNTNKHVEVNFIEKFTTERYFCPNTRCSITWFLSWSPCGECSRA
ITEFLSRYPHVTLFIYIARLYHHADPRNRQGLRDLISSGVTIQIMTEQESGYCWRNFVN
YSPSNEAHWPRYPHLWVRLYVLELYCIILGLPPCLNILRRKQPQLTFFTIALQSCHYQ
RLPPHILWATGLKSGGSSGGSSGSETPGTSESATPESSGGSSGGSDKKYSIGLAIGTNSVGWA
VITDEYKVPSKKFKVLGNTDRHSIKKNLIGALLFDSGETAEATRLKRTARRRYTRRKNRICYLQEI
FSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEKYPTIYHLRKKLVDSTDKA
DLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPINASGVDAKAILSA
RLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDDDLDNL
LAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLP
EKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNG
SIPHQIHLGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETIT
PWNFEEVVDKGASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPA
FLSGEQKKAIVDLLFKTNRKVTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKD
KDFLDNEENEDILEDIVLTLTLFEDREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLI
NGIRDKQSGKTILDFLKSDGFANRNFMQLIHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSP
AIKKGILQTVKVVDELVKVMGRHKPENIVIEMARENQTTQKGQKNSRERMKRIEEGIKELGSQI
LKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRLSDYDVDHIVPQSFLKDDSIDNKVLT
RSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTKAERGGLSELDKAGFIKRQL
VETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQFYKVREINNYHHAH
DAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIMNFFKTEIT
LANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESILPKRNS
DKLIARKKDWDPKKYGGFVSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDF
GSPEDNEQKQLFVEQHKHYLDEIIEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIH
LFTLTNLGAPAAFKYFDTTIDRIWYRSTKEVLDATLIHQSITGLYETRIDLSQLGGD
SGGSGGSG
DGSEFEPKKKRKV
MKRTADGSEFESPKKKRKV
SSETGPVAVDPTLRRRIEPHEFEVFFDPRELRKETCLLYEI
NWGGRHSIWRHTSQNTNKHVEVNFIEKFTTERYFCPNTRCSITWFLSWSPCGECSRA
ITEFLSRYPHVTLFIYIARLYHHADPRNRQGLRDLISSGVTIQIMTEQESGYCWRNFVN
YSPSNEAHWPRYPHLWVRLYVLELYCIILGLPPCLNILRRKQPQLTFFTIALQSCHYQ
RLPPHILWATGLKSGGSSGGSSGSETPGTSESATPESSGGSSGGSDKKYSIGLAIGTNSVGWA
VITDEYKVPSKKFKVLGNTDRHSIKKNLIGALLFDSGETAEATRLKRTARRRYTRRKNRICYLQEI
FSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEKYPTIYHLRKKLVDSTDKA
DLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPINASGVDAKAILSA
RLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDDDLDNL
LAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLP
EKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNG
SIPHQIHLGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETIT
PWNFEEVVDKGASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPA
FLSGEQKKAIVDLLFKTNRKVTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKD
KDFLDNEENEDILEDIVLTLTLFEDREMIEERLKTYAHLFDDKVMKQLKRRRYTGWGRLSRKLI
NGIRDKQSGKTILDFLKSDGFANRNFMQLIHDDSLTFKEDIQKAQVSGQGDSLHEHIANLAGSP
AIKKGILQTVKVVDELVKVMGRHKPENIVIEMARENQTTQKGQKNSRERMKRIEEGIKELGSQI
LKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRLSDYDVDHIVPQSFLKDDSIDNKVLT
RSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTKAERGGLSELDKAGFIKRQL
VETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQFYKVREINNYHHAH
DAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYSNIMNFFKTEIT
LANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESILPKRNS
DKLIARKKDWDPKKYGGFVSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIDF
LEAKGYKEVKKDLIIKLPKYSLFELENGRKRMLASARELQKGNELALPSKYVNFLYLASHYEKLK
GSPEDNEQKQLFVEQHKHYLDEIIEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIH
LFTLTNLGAPAAFKYFDTTIDRIWYRSTKEVLDATLIHQSITGLYETRIDLSQLGGD
SGGSGGSG
DGSEFEPKKKRKV
In some aspects, the base editing methods of the disclosure comprise the use of an adenine nucleobase editor. Exemplary adenine nucleobase editors include, but are not limited to, ABE7.10 (or ABEmax), ABE8e, ABE8e-SaKKH, ABE8e-NG, ABE-xCas9, ABE7.10-SaKKH, ABE7.10-NG, ABE7.10-VRQR, ABE7.10-VQR, ABE8e-NRTH, ABE8e-NRRH, ABE8e-VQR, or ABE8e-VRQR. In certain embodiments, the adenine nucleobase editor used in the disclosed methods is an ABE8e or an ABE7.10. ABE8e is sometimes referred to herein as “ABE8” or “ABE8.0”. The ABE8e nucleobase editor and variants thereof may comprise an adenosine deaminase domain containing a TadA-8e adenosine deaminase monomer (monomer form) or a TadA-8e adenosine deaminase homodimer or heterodimer (dimer form). Other ABEs may be used to deaminate an A nucleobase in accordance with the disclosed methods.
In some aspects, the disclosure provides complexes of adenine nucleobase editors and guide RNAs. Exemplary adenine nucleobase editors of the disclosed complexes include, but are not limited to, ABE7.10 (or ABEmax), ABE8e, ABE8e-SaKKH, ABE8e-NG, ABE-xCas9, ABE7.10-SaKKH, ABE7.10-NG, ABE7.10-VRQR, ABE7.10-VQR, ABE8e-NRTH, ABE8e-NRRH, ABE8e-VQR, or ABE8e-VRQR. In certain embodiments, the adenine nucleobase editor of any of the disclosed complexes is a ABE8e or an ABE7.10. Other ABEs may be used to deaminate a A nucleobase in accordance with the disclosed complexes.
The disclosed complexes of ABEs may possess an on-target editing efficiency of more than 50% after being contacted with a nucleic acid molecule comprising a target sequence. Further exemplary ABE complexes possess an on-target editing efficiency of more than 60% after being contacted with a nucleic acid molecule comprising a target sequence. Further exemplary ABEs possess an on-target editing efficiency of more than 65%, more than 70%, more than 75%, more than 80%, more than 82.5%, or more than 85% after being contacted with a nucleic acid molecule comprising a target sequence. The disclosed ABE complexes may exhibit indel frequencies of less than 0.75%, less than 0.6%, less than 0.5%, less than 0.4%, less than 0.3%, or less than 0.2% after being contacted with a nucleic acid molecule containing a target sequence.
Some aspects of the disclosure provide fusion proteins that comprise a nucleic acid programmable DNA binding protein (napDNAbp) and at least two adenosine deaminase domains. Without wishing to be bound by any particular theory, dimerization of adenosine deaminases (e.g., in cis or in trans) may improve the ability (e.g., efficiency) of the fusion protein to modify a nucleic acid base, for example to deaminate adenine. In some embodiments, any of the fusion proteins may comprise 2, 3, 4 or 5 adenosine deaminase domains. In some embodiments, any of the fusion proteins provided herein comprises two adenosine deaminases. In some embodiments, any of the fusion proteins provided herein contains only two adenosine deaminases. In some embodiments, the adenosine deaminases are the same. In some embodiments, the adenosine deaminases are any of the adenosine deaminases provided herein. In some embodiments, the adenosine deaminases are different.
In some embodiments, the first adenosine deaminase is any of the adenosine deaminases provided herein, and the second adenosine is any of the adenosine deaminases provided herein, but is not identical to the first adenosine deaminase. As one example, the fusion protein may comprise a first adenosine deaminase and a second adenosine deaminase that both comprise the amino acid sequence of SEQ ID NO: 10, which contains a W23R; H36L; P48A; R51L; L84F; A106V; D108N; H123Y; S146C; D147Y; R152P; E155V; I156F; and K157N mutation from ecTadA (SEQ ID NO: 1). In some embodiments, the fusion protein may comprise a first adenosine deaminase that comprises the amino acid sequence of SEQ ID NO: 1, and a second adenosine deaminase domain that comprises the amino acid sequence of TadA7.10 of SEQ ID NO: 10. In certain embodiments, the first and/or second deaminase is a TadA-8e deaminase. Additional fusion protein constructs comprising two adenosine deaminase domains are illustrated herein and are provided in the art.
In some embodiments, the fusion protein comprises two adenosine deaminases (e.g., a first adenosine deaminase and a second adenosine deaminase). In some embodiments, the fusion protein comprises a first adenosine deaminase and a second adenosine deaminase. In some embodiments, the first adenosine deaminase is N-terminal to the second adenosine deaminase in the fusion protein. In some embodiments, the first adenosine deaminase is C-terminal to the second adenosine deaminase in the fusion protein. In some embodiments, the first adenosine deaminase and the second deaminase are fused directly or via a linker. In some embodiments, the linker is any of the linkers provided herein, for example, any of the linkers described in the “Linkers” section. In some embodiments, the linker comprises the amino acid sequence of any one of SEQ ID NOs: 135-152. In some embodiments, the linker is 32 amino acids in length. In some embodiments, the linker comprises the amino acid sequence (SGGS)2-SGSETPGTSESATPES-(SGGS)2 (SEQ ID NO: 136), which may also be referred to as (SGGS)2-XTEN-(SGGS)2 (SEQ ID NO: 136). In some embodiments, the linker comprises the amino acid sequence (SGGS)n-SGSETPGTSESATPES-(SGGS)n (SEQ ID NO: 142), wherein n is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments, the first adenosine deaminase is the same as the second adenosine deaminase. In some embodiments, the first adenosine deaminase and the second adenosine deaminase are any of the adenosine deaminases described herein. In some embodiments, the first adenosine deaminase and the second adenosine deaminase are different. In some embodiments, the first adenosine deaminase is any of the adenosine deaminases provided herein. In some embodiments, the second adenosine deaminase is any of the adenosine deaminases provided herein but is not identical to the first adenosine deaminase. In some embodiments, the first adenosine deaminase is an ecTadA adenosine deaminase. In some embodiments, the first adenosine deaminase comprises an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the amino acid sequences set forth in any one of SEQ ID NOs: 1-10, or to any of the adenosine deaminases provided herein. In some embodiments, the first adenosine deaminase comprises the amino acid sequence of SEQ ID NO: 1. In some embodiments, the second adenosine deaminase comprises an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the amino acid sequences set forth in any one of SEQ ID NOs: 1-10, or to any of the adenosine deaminases provided herein. In some embodiments, the second adenosine deaminase comprises the amino acid sequence of SEQ ID NO: 10.
In some embodiments, the general architecture of exemplary fusion proteins with a first adenosine deaminase, a second adenosine deaminase, and a napDNAbp comprises any one of the following structures, where NLS is a nuclear localization sequence (e.g., any NLS provided herein), NH2 is the N-terminus of the fusion protein, and COOH is the C-terminus of the fusion protein.
Fusion proteins comprising a first adenosine deaminase, a second adenosine deaminase, and a napDNAbp.
NH2-[first adenosine deaminase]-[second adenosine deaminase]-[napDNAbp]-COOH;
NH2-[first adenosine deaminase]-[napDNAbp]-[second adenosine deaminase]-COOH;
NH2-[napDNAbp]-[first adenosine deaminase]-[second adenosine deaminase]-COOH;
NH2-[second adenosine deaminase]-[first adenosine deaminase]-[napDNAbp]-COOH;
NH2-[second adenosine deaminase]-[napDNAbp]-[first adenosine deaminase]-COOH;
NH2-[napDNAbp]-[second adenosine deaminase]-[first adenosine deaminase]-COOH.
In some embodiments, the fusion proteins provided herein do not comprise a linker. In some embodiments, a linker is present between one or more of the domains or proteins (e.g., first adenosine deaminase, second adenosine deaminase, and/or napDNAbp). In some embodiments, the “]-[” used in the general architecture above indicates the presence of an optional linker.
Fusion proteins comprising a first adenosine deaminase, a second adenosine deaminase, a napDNAbp, and an NLS.
Exemplary ABEs include, without limitation, the following fusion proteins. For the purposes of clarity, the adenosine deaminase domain may be shown in Bold; mutations of the ecTadA deaminase domain are shown in Bold underlining; the XTEN linker is shown in italics; the UGI/AAG/EndoV domains are shown in Bold italics; and NLS is shown in underlined italics:
In some embodiments, an A to G nucleobase editor comprises the structure of NH2-[second adenosine deaminase]-[first adenosine deaminase]-[dCas9]-COOH. In some embodiments, the second adenosine deaminase is a wile-type ecTadA (SEQ ID NO: 314). In some embodiments, the a linker is used between each domain. In some embodiments, the linker is 32 amino acids long and comprises the amino acid sequence of SGGSSGGSSGSETPGTSESATPESSGGSSGGS (SEQ ID NO: 384).
Exemplary adenine nucleobase editors comprise amino acid sequences that are at least least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.5% identical to any one of the amino acid sequences SEQ ID NOs: 379, 380, 382, 383, 386, and 388, 478 and 483. In particular embodiments, the disclosed adenine nucleobase editors comprise an amino acid sequence that is at least 90% identical to any of SEQ ID NOs: 388, 478, and 483. In particular embodiments, the disclosed adenine nucleobase editors comprise an amino acid sequence of any of SEQ ID NOs: 388, 478 and 483.
Non-limiting examples of A to G nucleobase editors are provided below, as SEQ ID NOs: 323-342, 379-383, 385-388, 458-478, 480, 483, and 553, provided below.
RAIGLHDPTAHAEIMALRQGGLVMQNYRLIDATLYVTFEPCVMCAGAMIHSRIGRVVFGVRNSKRGAAG
SLMNVLNYPGMNHRVEITEGILADECAALLCDFYRMPRQVFNAQKKAQSSINSGGSSGGSSGSETPGTS
ESATPESSGGSSGGSDKKYSIGLTIGTNSVGWAVITDEYKVPSKKFKVLGNTDRHSIKKNLIGALLFDSGE
TAEATRLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAY
HEKYPTIYHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEE
NPINASGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKD
TYDDDLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMVKRYDEHHQDLTLLKALVR
QQLPEKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNREDLLRKQRTFDNGII
PHQIHLGELHAILRRQGDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSRFAWMTRKSEETITPWNFEEV
VDKGASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELTKVKYVTEGMRKPAFLSGEQKKAIVDL
LFKTNRKVTVKQLKEDYFKKIECFDSVEISGVEDRFNASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLT
LTLFEDREMIEERLKTYAHLFDDKVMKQLKRLRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANR
NFMQLIHDDSLTFKEDIQKAQVSCQGDSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGGHKPENIVI
EMARENQTTQKGQKNSRERMKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDI
NRLSDYDVDHIVPQSFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDN
LTKAERGGLSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDF
QFYKVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFFYS
NIMNFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTGGFSKESIL
PKGNSDKLIARKKDWDPKKYGGFNSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITIMERSSFEKNPIGF
LEAKGYKEVKKDLIIKLPKYSLFELENGRKRMLASASVLHKGNELALPSKYVNFLYLASHYEKLKGSSEDN
KQKQLFVEQHKHYLDEHEQISEFSKRVILADANLDKVLSAYNKHRDKPIREQAENIIHLFTLTNLGASAAF
KYFDTTIGRKLYTSTKEVLDATLIHQSITGLYETRIDLSQLGGDSGGSKRTADGSEFEPKKKRKV
MKRTADGSEFESPKKKRKVSEVEFSHEYWMRHALTLAKRARDEREVPVGAVLVLNN
RVIGEGWNRAIGLHDPTAHAEIMALRQGGLVMQNYRLIDATLYVTFEPCVMCAGA
MIHSRIGRVVFGVRNSKRGAAGSLMNVLNYPGMNHRVEITEGILADECAALLCDFY
RMPRQVFNA
Q
KKAQSSIN
SGGSSGGSSGSETPGTSESATPESSGGSSGGSSEVEFSHEYWM
RHALTLAKRARDEREVPVGAVLVLNNRVIGEGWNRAIGLHDPTAHAEIMALRQGGLVMQNYRL
IDATLYVTFEPCVMCAGAMIHSRIGRVVFGVRNSKRGAAGSLMNVLNYPGMNHRVEITEGILAD
ECAALLCDFYRMPRQVFNAQKKAQSSINSGGSSGGSSGSETPGTSESATPESSGGSSGGSDKK
YSIGLTIGTNSVGWAVITDEYKVPSKKFKVLGNTDRHSIKKNLIGALLFDSGETAEATRLKRTARR
RYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEKYPTI
YHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEEN
PINASGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQ
LSKDTYDDDLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMVKRYDEHHQ
DLTLLKALVRQQLPEKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLN
REDLLRKQRTFDNGIIPHQIHLGELHAILRRQGDFYPFLKDNREKIEKILTFRIPYYVGPLARGNS
RFAWMTRKSEETITPWNFEEVVDKGASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNEL
TKVKYVTEGMRKPAFLSGEQKKAIVDLLFKTNRKVTVKQLKEDYFKKIECFDSVEISGVEDRFN
ASLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTLFEDREMIEERLKTYAHLFDDKVMKQLKR
LRYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFMQLIHDDSLTFKEDIQKAQVSCQG
DSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGGHKPENIVIEMARENQTTQKGQKNSRER
MKRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRLSDYDVDHIVPQ
SFLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTKAERGG
LSELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQF
YKVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYF
FYSNIMNFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQT
GGFSKESILPKGNSDKLIARKKDWDPKKYGGFNSPTAAYSVLVVAKVEKGKSKKLKSVKELLGIT
IMERSSFEKNPIGFLEAKGYKEVKKDLIIKLPKYSLFELENGRKRMLASAGVLHKGNELALPSKY
VNFLYLASHYEKLKGSPEDNEQKQLFVEQHKHYLDEIIEQISEFSKRVILADANLDKVLSAYNKH
RDKPIREQAENIIHLFTLTNLGVPAAFKYFD
TT
IDKKRYTSTKEVLDATLIHQSITGLYETRIDLSQ
LGGD
SGGSKRTADGSEFEPKKKRKV
SEVEFSHEYWMRHALTLAKRARDEREVPVGAVLVLNNRVI
GEGWNRAIGLHDPTAHAEIMALRQGGLVMQNYRLIDATLYVITEPCVMCAGAMIHSRIGRVVF
GVRNAKTGAAGSLMDVLHYPGMNHRVEITEGILADECAALLCYFFRMPRQVFNAQKKAQSSTD
DKKYSIGLAIGTNSVGWAVITDEYKVPSK
PKKKRKV
MKRTADGSEFESPKKKRKV
SEVEFSHEYWMRHALTLAKRARDEREVPVGAVLVLNN
RVIGEGWNRAIGLHDPTAHAEIMALR
Q
GGLVM
Q
NYRLIDATLYVTFEPCVMCAGA
MIHSRIGRVVFGVRNSKRGAAGSLMNVLNYPGMNHRVEITEGILADECAALLCDFY
RMPR
Q
VFNACIKKA
Q
SSIN
SGGSSGGSSGSETPGTSESATPESSGGSSGGSSEVEFSHEYWM
RHALTLAKRARDEREVPVGAVLVLNNRVIGEGWNRAIGLHDPTAHAEIMALRQGGLVMQNYRLI
DATLYVTFEPCVMCAGAMIHSRIGRVVFGVRNSKRGAAGSLMNVLNYPGMNHRVEITEGILADE
CAALLCDFYRMPRQVFNAQKKAQSSINSGGSSGGSSGSETPGTSESATPESSGGSSGGSDKKY
SIGLAIGTNSVGWAVITDEYKVPSKKFKVLGNTDRHSIKKNLIGALLFDSGETAEATRLKRTARRR
YTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHERHPIFGNIVDEVAYHEKYPTIY
HLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEGDLNPDNSDVDKLFIQLVQTYNQLFEENPI
NASGVDAKAILSARLSKSRRLENLIAQLPGEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQL
SKDTYDDDLDNLLAQIGDQYADLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQD
LTLLKALVRQQLPEKYKEIFFDQSKNGYAGYIDGGASQEEFYKFIKPILEKMDGTEELLVKLNRE
DLLRKQRTFDNGSIPHQIHLGELHAILRRQEDFYPFLKDNREKIEKILTFRIPYYVGPLARGNSR
FAWMTRKSEETITPWNFEEVVDKGASAQSFIERMTNFDKNLPNEKVLPKHSLLYEYFTVYNELT
KVKYVTEGMRKPAFLSGEQKKAIVDLLFKTNRKVTVKQLKEDYFKKIECFDSVEISGVEDRFNA
SLGTYHDLLKIIKDKDFLDNEENEDILEDIVLTLTLFEDREMIEERLKTYAHLFDDKVMKQLKRR
RYTGWGRLSRKLINGIRDKQSGKTILDFLKSDGFANRNFMQLIHDDSLTFKEDIQKAQVSGQG
DSLHEHIANLAGSPAIKKGILQTVKVVDELVKVMGRHKPENIVIEMARENQTTQKGQKNSRERM
KRIEEGIKELGSQILKEHPVENTQLQNEKLYLYYLQNGRDMYVDQELDINRLSDYDVDHIVPQS
FLKDDSIDNKVLTRSDKNRGKSDNVPSEEVVKKMKNYWRQLLNAKLITQRKFDNLTKAERGGL
SELDKAGFIKRQLVETRQITKHVAQILDSRMNTKYDENDKLIREVKVITLKSKLVSDFRKDFQFY
KVREINNYHHAHDAYLNAVVGTALIKKYPKLESEFVYGDYKVYDVRKMIAKSEQEIGKATAKYFF
YSNIMNFFKTEITLANGEIRKRPLIETNGETGEIVWDKGRDFATVRKVLSMPQVNIVKKTEVQTG
GFSKESILPKRNSDKLIARKKDWDPKKYGGFVSPTVAYSVLVVAKVEKGKSKKLKSVKELLGITI
MERSSFEKNPIDFLEAKGYKEVKKDLIIKLPKYSLFELENGRKRMLASARELQKGNELALPSKYV
NFLYLASHYEKLKGSPEDNEQKQLFVEQHKHYLDEIIEQISEFSKRVILADANLDKVLSAYNKHR
DKPIREQAENIIHLFTLTNLGAPAAFKYFDTTIDRKQYRSTKEVLDATLIHQSITGLYETRIDLSQL
GGDSGGSKRTADGSEFEPKKKRKV
For the full AAV genome sequences with that encode the CBE3.9max and ABEmax nucleobase editor constructs used in Examples 4 and 5, described below, see
In some embodiments, the N-terminal portion of a split nucleobase editor further comprises an inhibitor of uracil glycosylase (UGI). In some embodiments, the first nucleotide sequence encodes a polypeptide of the structure: NH2-[UGI]-[nucleobase modifying enzyme]-[N-terminal portion of dCas9 or nCas9]-[intein-N]. In some embodiments, the first nucleotide sequence encodes a polypeptide is of the structure: NH2-[nucleobase modifying enzyme]-[UGI]-[N-terminal portion of dCas9 or nCas9]-[intein-N].
In some embodiments, the C-terminal portion of a split nucleobase editor further comprises an enzyme that inhibits the activity of uracil glycosylase (UGI). In some embodiments, the second nucleotide sequence encodes a polypeptide of the structure: NH2-[intein-C]-[C-terminal portion of dCas9 or nCas9]-[UGI]-COOH. In some embodiments, the second nucleotide sequence encodes a polypeptide of the structure: NH2-[intein-C]-[C-terminal portion of dCas9 or nCas9]-[nucleobase modifying enzyme]-[UGI]-COOH. In some embodiments, the second nucleotide sequence encodes a polypeptide of the structure: NH2-[intein-C]-[C-terminal portion of dCas9 or nCas9]-[UGI]-[nucleobase modifying enzyme]-COOH.
Non-limiting, exemplary uracil glycosylase inhibitor sequences are provided below.
Bacillus phage PBS2 (Bacteriophage PBS2) Uracil-
Erwinia tasmaniensis SSB (themostable single-
In some embodiments, when the N-terminal portion and the C-terminal portion of the nucleobase are joined, to form a complete split nucleobase editor. In some embodiments, the split nucleobase editor may comprise any one of the following structures:
NH2-[nucleobase modifying enzyme]-[dCas9 or nCas9]-COOH
NH2-[UGI]-[nucleobase modifying enzyme]-[dCas9 or nCas9]-COOH
NH2-[nucleobase modifying enzyme]-[UGI]-[dCas9 or nCas9]-COOH
NH2-[nucleobase modifying enzyme]-[dCas9 or nCas9]-[UGI]-COOH
NH2-[dCas9 or nCas9]-[nucleobase modifying enzyme]-COOH
NH2-[UGI]-[dCas9 or nCas9]-[nucleobase modifying enzyme]-COOH
NH2-[dCas9 or nCas9]-[UGI]-[nucleobase modifying enzyme]-COOH or
NH2-[dCas9 or nCas9]-[nucleobase modifying enzyme]-[UGI]-COOH.
In some embodiments, the first nucleotide sequence or the second nucleotide sequence (encoding either the split Cas9 protein or the split nucleobase editor) is operably linked to a nucleotide sequence encoding at least one bipartite nuclear localization signal (NLS). For example, the first nucleotide sequence may be operably linked to a nucleotide sequence encoding one or more (e.g., 2, 3, 4, 5, or more) bipartite NLS. In some embodiments, the second nucleotide sequence may be operably linked to a nucleotide sequence encoding one or more (e.g., 2, 3, 4, 5, or more) bipartite NLSs. As such, the split Cas9 or split nucleobase editor formed by joining the N-terminal portion and the C-terminal portion may comprise one or more bipartite NLSs. For example, the split Cas9 or split nucleobase editor may comprise any one of the following structures (bNLS means one or more bipartite nuclear localization signals):
NH2-bNLS-[Cas9]-COOH
NH2-[Cas9]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-COOH
NH2-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-COOH
NH2-[nucleobase modifying enzyme]-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-COOH
NH2-bNLS-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[UGI]-[nucleobase modifying enzyme]-[dCas9 or nCas9]-COOH
NH2-[UGI]-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-COOH
NH2-[UGI]-[nucleobase modifying enzyme]-bNLS[dCas9 or nCas9]-COOH
NH2-[UGI]-[nucleobase modifying enzyme]-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[UGI]-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-COOH
NH2-bNLS-[UGI]-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-COOH
NH2-bNLS-[UGI]-[nucleobase modifying enzyme]-[dCas9 or nCas9]-bNLS-COOH
NH2-[UGI]-bNLS-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-COOH
NH2-[UGI]-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-bNLS-COOH
NH2-[UGI]-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[UGI]-bNLS-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-COOH
NH2-bNLS-[UGI]-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-bNLS-COOH
NH2-[UGI]-bNLS-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[UGI]-bNLS-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[UGI]-[dCas9 or nCas9]-COOH
NH2-[nucleobase modifying enzyme]-bNLS-[UGI]-[dCas9 or nCas9]-COOH
NH2-[nucleobase modifying enzyme]-[UGI]-bNLS-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-bNLS-[UGI]-[dCas9 or nCas9]-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[UGI]-bNLS-[dCas9 or nCas9]-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[UGI]-[dCas9 or nCas9]-bNLS-COOH
NH2-[nucleobase modifying enzyme]-bNLS-[UGI]-bNLS-[dCas9 or nCas9]-COOH
NH2-[nucleobase modifying enzyme]-bNLS-[UGI]-[dCas9 or nCas9]-bNLS-COOH
NH2-[nucleobase modifying enzyme]-[UGI]-bNLS-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-bNLS-[UGI]-bNLS-[dCas9 or nCas9]-COOH
NH2-bNLS-[nucleobase modifying enzyme]-bNLS-[UGI]-[dCas9 or nCas9]-bNLS-COOH
NH2-[nucleobase modifying enzyme]-bNLS-[UGI]-bNLS-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-bNLS-[UGI]-bNLS-[dCas9 or nCas9]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-[UGI]-COOH
NH2-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-[UGI]-COOH
NH2-[nucleobase modifying enzyme]-[dCas9 or nCas9]-bNLS-[UGI]-COOH
NH2-[nucleobase modifying enzyme]-[dCas9 or nCas9]-[UGI]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-[UGI]-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-bNLS-[UGI]-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-[UGI]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-bNLS-[UGI]-COOH
NH2-bNLS-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-[UGI]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-[dCas9 or nCas9]-bNLS-[UGI]-bNLS-COOH
NH2-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-bNLS-[UGI]-bNLS-COOH
NH2-bNLS-[nucleobase modifying enzyme]-bNLS-[dCas9 or nCas9]-bNLS-[UGI]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-COOH
NH2-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-[dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[UGI][dCas9 or nCas9]-[nucleobase modifying enzyme]-COOH
NH2-[UGI]-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-COOH
NH2-[UGI][dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-[UGI][dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[UGI]-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-COOH
NH2-bNLS-[UGI][dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-bNLS-[UGI][dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-[UGI]-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-[UGI]-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-[UGI][dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[UGI]-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-bNLS-[UGI][dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[UGI]-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-[UGI]-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[UGI]-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-[UGI]-[nucleobase modifying enzyme]-COOH
NH2-[dCas9 or nCas9]-bNLS-[UGI]-[nucleobase modifying enzyme]-COOH
NH2-[dCas9 or nCas9]-[UGI]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-[dCas9 or nCas9]-[UGI]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-bNLS[UGI]-[nucleobase modifying enzyme]-COOH
NH2-bNLS-[dCas9 or nCas9]-[UGI]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-bNLS-[dCas9 or nCas9]-[UGI]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-[dCas9 or nCas9]-bNLS-[UGI]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-[dCas9 or nCas9]-bNLS-[UGI]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-[dCas9 or nCas9]-[UGI]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-bNLS-[UGI]-bNLS-[nucleobase modifying enzyme]-COOH
NH2-bNLS-[dCas9 or nCas9]-bNLS-[UGI]-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-[UGI]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-[dCas9 or nCas9]-bNLS-[UGI]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-bNLS-[UGI]-bNLS-[nucleobase modifying enzyme]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-[UGI]-COOH
NH2-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-[UGI]-COOH
NH2-[dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-[UGI]-COOH
NH2-[dCas9 or nCas9]-[nucleobase modifying enzyme]-[UGI]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-[UGI]-COOH
NH2-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-[UGI]-COOH
NH2-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-[UGI]-bNLS-COOH
NH2-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-[UGI]-COOH
NH2-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-[UGI]-bNLS-COOH
NH2-[dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-[UGI]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-[UGI]-COOH
NH2-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-[UGI]-bNLS-COOH
NH2-bNLS-[dCas9 or nCas9]-[nucleobase modifying enzyme]-bNLS-[UGI]-bNLS-COOH
NH2-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-[UGI]-bNLS-COOH
or
NH2-bNLS-[dCas9 or nCas9]-bNLS-[nucleobase modifying enzyme]-bNLS-[UGI]-bNLS-COOH
Herein, “NH2—” represents the N-terminus of a protein or polypeptide, and “—COOH” represents the C-terminus of a protein or polypeptide. “]-[” represents a peptide bond or a linker. In some embodiments, linkers may be used to link any of the protein or protein domains described herein. The linker may be as simple as a covalent bond, or it may be a polymeric linker many atoms in length. In some embodiments, the linker is a polypeptide or based on amino acids. In some embodiments, the linker is not peptide-like. In some embodiments, the linker is a covalent bond (e.g., a carbon-carbon bond, disulfide bond, carbon-heteroatom bond, etc.). In some embodiments, the linker is a carbon-nitrogen bond of an amide linkage. In some embodiments, the linker is a cyclic or acyclic, substituted or unsubstituted, branched or unbranched aliphatic or heteroaliphatic linker. In some embodiments, the linker is polymeric (e.g., polyethylene, polyethylene glycol, polyamide, polyester, etc.). In some embodiments, the linker comprises a monomer, dimer, or polymer of aminoalkanoic acid. In some embodiments, the linker comprises an aminoalkanoic acid (e.g., glycine, ethanoic acid, alanine, beta-alanine, 3-aminopropanoic acid, 4-aminobutanoic acid, 5-pentanoic acid, etc.). In some embodiments, the linker comprises a monomer, dimer, or polymer of aminohexanoic acid (Ahx). In some embodiments, the linker is based on a carbocyclic moiety (e.g., cyclopentane, cyclohexane). In some embodiments, the linker comprises a polyethylene glycol moiety (PEG). In some embodiments, the linker comprises amino acids. In some embodiments, the linker comprises a peptide. In some embodiments, the linker comprises an aryl or heteroaryl moiety. In some embodiments, the linker is based on a phenyl ring. The linker may include functionalized moieties to facilitate attachment of a nucleophile (e.g., thiol, amino) from the peptide to the linker. Any electrophile may be used as part of the linker. Exemplary electrophiles include, but are not limited to, activated esters, activated amides, Michael acceptors, alkyl halides, aryl halides, acyl halides, and isothiocyanates.
In some embodiments, the linker is an amino acid or a plurality of amino acids (e.g., a peptide or protein). In some embodiments, the linker is a bond (e.g., a covalent bond), an organic molecule, group, polymer, or chemical moiety. In some embodiments, the linker is 5-100 amino acids in length, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 30-35, 35-40, 40-45, 45-50, 50-60, 60-70, 70-80, 80-90, 90-100, 100-110, 110-120, 120-130, 130-140, 140-150, or 150-200 amino acids in length. Longer or shorter linkers are also contemplated. In some embodiments, a linker comprises the amino acid sequence SGSETPGTSESATPES (SEQ ID NO: 377), which may also be referred to as the XTEN linker. In some embodiments, a linker comprises the amino acid sequence: SGGS (SEQ ID NO: 378). In some embodiments, a linker comprises the amino acid sequence: (SGGS)n (SEQ ID NO: 557), (GGGS)n (SEQ ID NO: 558), (GGGGS)n (SEQ ID NO: 559), (G)n (SEQ ID NO: 390), (EAAAK). (SEQ ID NO: 560), (GGS)n (SEQ ID NO: 562), SGSETPGTSESATPES (SEQ ID NO: 377), or (XP)n (SEQ ID NO: 563) motif, or a combination of any of these, wherein n is independently an integer between 1 and 30, inclusive, and wherein X is any amino acid. In some embodiments, n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. In some embodiments, the linker comprises the amino acid sequence: SGSETPGTSESATPES (SEQ ID NO: 377), and SGGS (SEQ ID NO: 378). In some embodiments, the linker comprises the amino acid sequence: SGGSSGSETPGTSESATPESSGGS (SEQ ID NO: 561). In some embodiments, a linker comprises the amino acid sequence: SGGSSGGSSGSETPGTSESATPESSGGSSGGS (SEQ ID NO: 384). In some embodiments, a linker comprises the amino acid sequence: GGSGGSPGSPAGSPTSTEEGTSESATPESGPGTSTEPSEGSAPGSPAGSPTSTEEGTSTEPSE GSAPGTSTEPSEGSAPGTSESATPESGPGSEPATSGGSGGS (SEQ ID NO: 564).
In some embodiments, the linker is 24 amino acids in length. In some embodiments, the linker comprises the amino acid sequence SGGSSGGSSGSETPGTSESATPES (SEQ ID NO: 343). In some embodiments, the linker is 40 amino acids in length. In some embodiments, the linker comprises the amino acid sequence SGGSSGGSSGSETPGTSESATPESSGGSSGGSSGGSSGGS (SEQ ID NO: 391). In some embodiments, the linker is 64 amino acids in length. In some embodiments, the linker comprises the amino acid sequence SGGSSGGSSGSETPGTSESATPESSGGSSGGSSGGSSGGSSGSETPGTSESATPESSGGSSGG S (SEQ ID NO: 392). In some embodiments, the linker is 92 amino acids in length. In some embodiments, the linker comprises the amino acid sequence PGSPAGSPTSTEEGTSESATPESGPGTSTEPSEGSAPGSPAGSPTSTEEGTSTEPSEGSAPGTS TEPSEGSAPGTSESATPESGPGSEPATS (SEQ ID NO: 393).
In some embodiments, the first and second nucleotide sequences are on the same nucleic acid vector. In some embodiments, the first and second nucleotide sequences are on different nucleic acid vectors. In some embodiments, the vector is a plasmid. In some embodiments, the nucleic acid vector is a recombinant genome of a adeno-associated virus (rAAV). In some embodiments, the nucleic acid vector is the genome of an adeno-associated virus packaged in a rAAV particle. In some embodiments, the first and/or the second nucleotide sequence is operably linked to a promoter. In some embodiments, the nucleic acid vector further comprise a nucleotide sequence encoding one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) gRNAs operably linked to a promoter. In some embodiments, the promoter is a constitutive promoter. In some embodiments, the promoter is an inducible promoter.
An inducible promoter of the present disclosure may be induced by (or repressed by) one or more physiological condition(s), such as changes in light, pH, temperature, radiation, osmotic pressure, saline gradients, cell surface binding, and the concentration of one or more extrinsic or intrinsic inducing agent(s). An extrinsic inducer signal or inducing agent may comprise, without limitation, amino acids and amino acid analogs, saccharides and polysaccharides, nucleic acids, protein transcriptional activators and repressors, cytokines, toxins, petroleum-based compounds, metal containing compounds, salts, ions, enzyme substrate analogs, hormones, or combinations thereof.
Inducible promoters of the present disclosure include any inducible promoter described herein or known to one of ordinary skill in the art. Examples of inducible promoters include, without limitation, chemically/biochemically-regulated and physically-regulated promoters such as alcohol-regulated promoters, tetracycline-regulated promoters (e.g., anhydrotetracycline (aTc)-responsive promoters and other tetracycline-responsive promoter systems, which include a tetracycline repressor protein (tetR), a tetracycline operator sequence (tetO) and a tetracycline transactivator fusion protein (tTA)), steroid-regulated promoters (e.g., promoters based on the rat glucocorticoid receptor, human estrogen receptor, moth ecdysone receptors, and promoters from the steroid/retinoid/thyroid receptor superfamily), metal-regulated promoters (e.g., promoters derived from metallothionein (proteins that bind and sequester metal ions) genes from yeast, mouse and human), pathogenesis-regulated promoters (e.g., induced by salicylic acid, ethylene or benzothiadiazole (BTH)), temperature/heat-inducible promoters (e.g., heat shock promoters), and light-regulated promoters (e.g., light responsive promoters from plant cells). Other inducible promoter systems are known in the art and may be used in accordance with the present disclosure.
In some embodiments, inducible promoters of the present disclosure function in prokaryotic cells (e.g., bacterial cells). Examples of inducible promoters for use prokaryotic cells include, without limitation, bacteriophage promoters (e.g. Pls icon, T3, T7, SP6, PL) and bacterial promoters (e.g., Pbad, PmgrB, Ptrc2, Plac/ara, Ptac, Pm), or hybrids thereof (e.g. PLlacO, PLtetO). Examples of bacterial promoters for use in accordance with the present disclosure include, without limitation, positively regulated E. coli promoters, such as positively regulated 670 promoters (e.g., inducible pBad/araC promoter, Lux cassette right promoter, modified lamdba Prm promote, plac Or2-62 (positive), pBad/AraC with extra REN sites, pBad, P(Las) TetO, P(Las) CIO, P(Rhl), Pu, FecA, pRE, cadC, hns, pLas, pLux), GS promoters (e.g., Pdps), 632 promoters (e.g., heat shock), and 654 promoters (e.g., glnAp2); negatively regulated E. coli promoters such as negatively regulated 670 promoters (e.g., Promoter (PRM+), modified lamdba Prm promoter, TetR-TetR-4C P(Las) TetO, P(Las) CIO, P(Lac) IQ, RecA_DlexO_DLacO1, dapAp, FecA, Pspac-hy, pcI, plux-cI, plux-lac, CinR, CinL, glucose controlled, modified Pr, modified Prm+, FecA, Pcya, rec A (SOS), Rec A (SOS), EmrR_regulated, BetI_regulated, pLac_lux, pTet_Lac, pLac/Mnt, pTet/Mnt, LsrA/cI, pLux/cI, LacI, LacIQ, pLacIQ1, pLas/cI, pLas/Lux, pLux/Las, pRecA with LexA binding site, reverse BBa_R0011, pLacI/ara-1, pLacIq, rrnB P1, cadC, hns, PfhuA, pBad/araC, nhaA, OmpF, RcnR), σS promoters (e.g., Lutz-Bujard LacO with alternative sigma factor σ38), σ32 promoters (e.g., Lutz-Bujard LacO with alternative sigma factor σ32), and σ54 promoters (e.g., glnAp2); negatively regulated B. subtilis promoters such as repressible B. subtilis σA promoters (e.g., Gram-positive IPTG-inducible, Xyl, hyper-spank) and σB promoters. Other inducible microbial promoters may be used in accordance with the present disclosure.
In some embodiments, inducible promoters of the present disclosure function in eukaryotic cells (e.g., mammalian cells). Examples of inducible promoters for use eukaryotic cells include, without limitation, chemically-regulated promoters (e.g., alcohol-regulated promoters, tetracycline-regulated promoters, steroid-regulated promoters, metal-regulated promoters, and pathogenesis-related (PR) promoters) and physically-regulated promoters (e.g., temperature-regulated promoters and light-regulated promoters).
The present disclosure further provides guide RNAs for use in accordance with the disclosed base editors and methods of editing. The disclosure provides guide RNAs that are designed to recognize target sequences. Such gRNAs may be designed to have guide sequences (or “spacers”) having complementarity to a protospacer within the target sequence. Guide RNAs are also provided for use with one or more of the disclosed fusion proteins, e.g., in the disclosed methods of editing a nucleic acid molecule. Such gRNAs may be designed to have guide sequences having complementarity to a protospacer within a target sequence to be edited, and to have backbone sequences that interact specifically with the napDNAbp domains of any of the disclosed nucleobase editors, such as Cas9 nickase domains of the disclosed nucleobase editors.
The disclosure further provides methods for editing a target nucleic acid molecule, e.g., a single nucleobase within a genome, with a nucleobase editor described herein, e.g., a split nucleobase editor. Such methods involve transducing (e.g., via transfection) cells with a plurality of complexes each comprising a fusion protein (e.g., a fusion protein comprising a Cas9 nickase (nCas9) domain and an adenosine deaminase domain) and a gRNA molecule. In some embodiments, the gRNA is bound to the napDNAbp domain (e.g., nCas9 domain) of the fusion protein. In some embodiments, each gRNA comprises a guide sequence of at least 10 contiguous nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 contiguous nucleotides) that is complementary to a target sequence. In certain embodiments, the methods involve the transfection of nucleic acid constructs (e.g., plasmids) that each (or together) encode the components of a complex of fusion protein and gRNA molecule.
Some aspects of the invention relate to guide sequences (“guide RNA” or “gRNA”) that are capable of guiding a napDNAbp or a nucleobase editor comprising a napDNAbp to a target site, e.g. a target site in the NPC1 gene or TMC1 gene. Exemplary guide sequences suitable for targeting the NPC1 and Tmc1 genes and used in the experiments of Examples 1-4 are provided in Table 6 (SEQ ID NOs: 669-743). The guide RNA may be 15-100 nucleotides in length and comprise a sequence of at least 10, at least 15, or at least 20 contiguous nucleotides that is complementary to a target nucleotide sequence. The guide RNA may comprise a sequence of 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 contiguous nucleotides that is complementary to a target nucleotide sequence.
In other aspects, the present specification provides complexes comprising the nucleobase editors described herein and a gRNA bound to the Cas9 domain of the fusion protein, such as a single guide RNA. In various embodiments, nucleobase editors (e.g., the split nucleobase editors provided herein) can be complexed, bound, or otherwise associated with (e.g., via any type of covalent or non-covalent bond) one or more guide sequences, i.e., the sequence which becomes associated or bound to the nucleobase editor and directs its localization to a specific target sequence having complementarity to the guide sequence or a portion thereof. The particular design aspects of a guide sequence will depend upon the nucleotide sequence of a genomic target site of interest (e.g., in human NPC) and the type of napDNA/RNAbp (e.g., type of Cas protein) present in the nucleobase editor, among other factors, such as PAM sequence locations, percent G/C content in the target sequence, the degree of microhomology regions, secondary structures, etc. Accordingly, in some embodiments, the disclosure provides compositions comprising complexes any of the disclosed nucleobase editors and a guide RNA comprising a guide sequence comprising a nucleotide sequence of any of SEQ ID NOs: 669-743. In some embodiments of the disclosed complexes, the guide RNA comprises a sequence that differs from any of SEQ ID NOs: 669-743 by no more than 1, 2, 3, or 4 nucleotides.
In some embodiments, the disclosure provides compositions comprising i) vectors encoding any of the disclosed nucleobase editors and ii) a guide RNA comprising a guide sequence comprising a nucleotide sequence of any of SEQ ID NOs: 669-743. In some embodiments, these vectors comprise i) a nucleic acid encoding an N-terminal portion of a split nucleobase editor, ii) a nucleic acid encoding a C-terminal portion of a split nucleobase editor, and iii) a guide RNA comprising a guide sequence comprising a nucleotide sequence of any of SEQ ID NOs: 669-743. In some embodiments of the disclosed vectors, the guide RNA comprises a sequence that differs from any of SEQ ID NOs: 669-743 by no more than 1, 2, 3, or 4 nucleotides.
The present disclosure also provides compositions of guide RNAs. In particular embodiments, the disclosure provides compositions of guide RNAs comprising a guide sequence comprising a nucleotide sequence of any of SEQ ID NOs: 669-743. The present disclosure also provides methods of editing target DNA sequences in an NPC1 gene or a TMC1 gene using compositions and/or complexes comprising any of the disclosed guide RNAs.
In some embodiments, a guide sequence is less than about 35, 30, 25, 20, 15, 12, or fewer nucleotides in length. The ability of a guide sequence to direct sequence-specific binding of a nucleobase editor to a target sequence may be assessed by any suitable assay. For example, the components of a nucleobase editor, including the guide sequence to be tested, may be provided to a host cell having the corresponding target sequence (e.g., a HGADFN 167 or HGADFN 188 cell line), such as by transfection with vectors encoding the components of a nucleobase editor disclosed herein, followed by an assessment of preferential cleavage within the target sequence. Similarly, cleavage of a target polynucleotide sequence may be evaluated in a test tube by providing the target sequence, components of a nucleobase editor, including the guide sequence to be tested and a control guide sequence different from the test guide sequence, and comparing binding or rate of cleavage at the target sequence between the test and control guide sequence reactions. Other assays are possible, and will occur to those skilled in the art.
In addition to the SDS, the gRNA comprises a scaffold sequence (corresponding to the tracrRNA in the native CRISPR/Cas system) that is required for its association with Cas9 (sometimes referred to herein as the “gRNA handle,” “gRNA core” or “gRNA backbone”). In various embodiments, the guide RNA scaffold binds an S. pyogenes Cas9. In other embodiments, the guide RNA scaffold binds an S. aureus Cas9. In some embodiments, the guide RNAs for use in accordance with the disclosed methods of editing comprise a backbone structure that is recognized by an S. pyogenes Cas9 protein or domain, such as an SpCas9 domain of the disclosed nucleobase editors. The backbone structure recognized by an SpCas9 protein may comprise the sequence 5′-[guide sequence]-guuuuagagcuagaaauagcaaguuaaaauaaggcuaguccguuaucaacuugaaaaaguggcaccgagucggugcuuuuu-3′ (SEQ ID NO: 443), wherein the guide sequence comprises a sequence that is complementary to the protospacer of the target sequence. See U.S. Publication No. 2015/0166981, published Jun. 18, 2015, the disclosure of which is incorporated by reference herein. In other embodiments, the guide RNAs for use in accordance with the disclosed methods of editing comprise a backbone structure that is recognized by an S. aureus Cas9 protein. The backbone structure recognized by an SaCas9 protein may comprise the sequence 5′-[guide sequence]-guuuuaguacucuguaaugaaaauuacagaaucuacuaaaacaaggcaaaaugccguguuuaucucgucaacuuguuggcgag auuuuuuu-3′ (SEQ ID NO: 565).
In other embodiments, the guide RNAs for use in accordance with the disclosed methods of editing comprise a backbone structure that is recognized by an Lachnospiraceae bacterium Cas12a protein. The backbone structure recognized by an LbCas12a protein may comprise the sequence 5′-[guide sequence]-uaauuucuacuaaguguagau-3′ (SEQ ID NO: 566). In other embodiments, the guide RNAs for use in accordance with the disclosed methods of editing comprise a backbone structure that is recognized by an Acidaminococcus sp. BV3L6 Cas12a protein. The backbone structure recognized by an AsCas12a protein may comprise the sequence 5′-[guide sequence]-uaauuucuacucuuguagau-3′ (SEQ ID NO: 567).
Other non-limiting, suitable gRNA scaffold sequences that may be used in accordance with the present disclosure are listed in Table 2. In other embodiments, the guide RNAs for use in accordance with the disclosed methods of editing comprise a backbone structure that comprises any of SEQ ID NOs: 359-361, 363, 366, 368, and 569-575.
S. pyogenes
S. pyogenes
S.
thermophilus
S.
thermophilus
C. jejuni
F. novicida
S.
thermophilus2
M. mobile
L. innocua
S. pyogenes
S. mutans
S.
thermophilus
N.
meningitidis
P. multocida
In some embodiments, a guide sequence is selected to reduce the degree of secondary structure within the guide sequence. Secondary structure may be determined by any suitable polynucleotide folding algorithm. Some programs are based on calculating the minimal Gibbs free energy. An example of one such algorithm is mFold, as described by Zuker and Stiegler (Nucleic Acids Res. 9 (1981), 133-148). Another example folding algorithm is the online webserver RNAfold, developed at Institute for Theoretical Chemistry at the University of Vienna, using the centroid structure prediction algorithm (see, e.g., A. R. Gruber et al., 2008, Cell 106(1): 23-24; and P A Carr & G M Church, 2009, Nature Biotechnology 27(12): 1151-62). Additional algorithms may be found in Chuai, G. et al., DeepCRISPR: optimized CRISPR guide RNA design by deep learning, Genome Biol. 19:80 (2018), and PCT Application No. PCT/US2018/065886 and U.S. Pat. No. 8,871,445, issued Oct. 28, 2014, the entireties of each of which are incorporated herein by reference.
In general, a tracr mate sequence includes any sequence that has sufficient complementarity with a tracr sequence to promote one or more of: (1) excision of a guide sequence flanked by tracr mate sequences in a cell containing the corresponding tracr sequence; and (2) formation of a complex at a target sequence, wherein the complex comprises the tracr mate sequence hybridized to the tracr sequence. In general, degree of complementarity is with reference to the optimal alignment of the tracr mate sequence and tracr sequence, along the length of the shorter of the two sequences. Optimal alignment may be determined by any suitable alignment algorithm, and may further account for secondary structures, such as self-complementarity within either the tracr sequence or tracr mate sequence. In some embodiments, the degree of complementarity between the tracr sequence and tracr mate sequence along the length of the shorter of the two when optimally aligned is about or more than about 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 97.5%, 99%, or higher. In some embodiments, the tracr sequence is about or more than about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 40, 50, or more nucleotides in length. In some embodiments, the tracr sequence and tracr mate sequence are contained within a single transcript, such that hybridization between the two produces a transcript having a secondary structure, such as a hairpin. Preferred loop forming sequences for use in hairpin structures are four nucleotides in length, and most preferably have the sequence GAAA. However, longer or shorter loop sequences may be used, as may alternative sequences. The sequences preferably include a nucleotide triplet (for example, AAA), and an additional nucleotide (for example C or G). Examples of loop forming sequences include CAAA and AAAG. In an embodiment of the invention, the transcript or transcribed polynucleotide sequence has at least two or more hairpins. In preferred embodiments, the transcript has two, three, four or five hairpins. In a further embodiment of the invention, the transcript has at most five hairpins. In some embodiments, the single transcript further includes a transcription termination sequence; preferably this is a polyT sequence, for example six T nucleotides. Further non-limiting examples of single polynucleotides comprising a guide sequence, a tracr mate sequence, and a tracr sequence are as follows (listed 5′ to 3′), where “N” represents a base of a guide sequence, the first block of lower case letters represent the tracr mate sequence, and the second block of lower case letters represent the tracr sequence, and the final poly-T sequence represents the transcription terminator: (1) NNNNNNNNgtttttgtactctcaagatttaGAAAtaaatcttgcagaagctacaaagataaggctt catgccgaaatcaacaccctgtcattttatggcagggtgttttcgttatttaaTTTTTT (SEQ ID NO: 201); (2) NNNNNNNNNNNNNNNNNNgtttttgtactctcaGAAAtgcagaagctacaaagataaggcttcatgccgaaatca acaccctgtcattttatggcagggtgttttcgttatttaaTTTTTT (SEQ ID NO: 202); (3) NNNNNNNNNNNNNNNNNNNNgtttttgtactctcaGAAAtgcagaagctacaaagataaggcttcatgccgaaatca acaccctgtcattttatggcagggtgtTTTTT (SEQ ID NO: 203); (4) NNNNNNNNNNNNNNNNNNNNgttttagagctaGAAAtagcaagttaaaataaggctagtccgttatcaacttgaaaa agtggcaccgagtcggtgcTTTTTT (SEQ ID NO: 204); (5) NNNNNNNNNNNNNNNNNNNNgttttagagctaGAAATAGcaagttaaaataaggctagtccgttatcaacttgaa aaagtgTTTTTTT (SEQ ID NO: 205); and (6) NNNNNNNNNNNNNNNNNNNNgttttagagctagAAATAGcaagttaaaataaggctagtccgttatcaTTTTTT TT (SEQ ID NO: 206). In some embodiments, sequences (1) to (3) are used in combination with Cas9 from S. thermophilus CRISPR. In some embodiments, sequences (4) to (6) are used in combination with Cas9 from S. pyogenes. In some embodiments, the tracr sequence is a separate transcript from a transcript comprising the tracr mate sequence.
It will be apparent to those of skill in the art that in order to target any of the fusion proteins comprising a Cas9 domain and a deaminase, as disclosed herein, to a target site to be edited, it is typically necessary to co-express the fusion protein together with a guide RNA, e.g., an sgRNA. As explained in more detail elsewhere herein, a guide RNA typically comprises a tracrRNA framework allowing for Cas9 binding, and a guide sequence, which confers sequence specificity to the Cas9:nucleic acid editing enzyme/domain fusion protein.
Recombinant Adeno-Associated Viral (rAAV) Vectors
Some aspects of the present disclosure relate to using recombinant adeno-associated virus vectors for the delivery of a split Cas9 protein or a split nucleobase editor into a cell. The N-terminal portion of the Cas9 protein or the nucleobase editor and the C-terminal portion of the Cas9 protein or the nucleobase editor are delivered by separate rAAV vectors or particles into the same cell, since the full-length Cas9 protein or nucleobase editors exceeds the packaging limit of rAAV (˜4.9 kb).
As such, in some embodiments, a composition for delivering the split Cas9 protein or split nucleobase editor into a cell (e.g., a mammalian cell, a human cell) is provided. In some embodiments, the composition of the present disclosure comprises: (i) a first recombinant adeno-associated virus (rAAV) particle comprising a first nucleotide sequence encoding a N-terminal portion of a Cas9 protein or nucleobase editor fused at its C-terminus to an intein-N; and (ii) a second recombinant adeno-associated virus (rAAV) particle comprising a second nucleotide sequence encoding an intein-C fused to the N-terminus of a C-terminal portion of the Cas9 protein or nucleobase editor. The rAAV particles of the present disclosure comprise a rAAV vector (i.e., a recombinant genome of the rAAV) encapsidated in the viral capsid proteins.
In some embodiments, any of the disclosed rAAV vectors encoding the N-terminal portions or the C-terminal portions of the split nucleobase editors may comprise a nucleotide sequence that is at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the sequences depicted in
In some embodiments, any of the disclosed nucleic acid molecules encoding an N-terminal portion of a nucleobase editor fused at its C-terminus to an intein-N may comprise a nucleotide sequence that is at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the nucleotide sequences of SEQ ID NOs: 642, 644, 646, 648, 650, and 652. In some embodiments, any of the disclosed nucleic acid molecules encoding an N-terminal portion of a nucleobase editor may comprise a nucleotide sequence that differs by about 10, 15, 20, 25, 30, 35, 40, 45, 50, or more than 50 nucleotides from any one of the sequences of SEQ ID NOs: 642, 644, 646, 648, 650, and 652. In particular embodiments, any of the disclosed nucleic acid molecules encoding an N-terminal portion of a nucleobase editor fused at its C-terminus to an intein-N may comprise a nucleotide sequence that comprises any one of the sequences of SEQ ID NOs: 642, 644, 646, 648, 650, and 652.
In some embodiments, any of the disclosed nucleic acid molecules encoding a C-terminal portion of a nucleobase editor fused at its N-terminus to an intein-C may comprise a nucleotide sequence that is at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the nucleotide sequences of SEQ ID NOs: 643, 645, 647, 649, 651, and 653. In some embodiments, any of the disclosed nucleic acid molecules encoding a C-terminal portion of a nucleobase editor may comprise a nucleotide sequence that differs by about 10, 15, 20, 25, 30, 35, 40, 45, 50, or more than 50 nucleotides from any one of the sequences of SEQ ID NOs: 643, 645, 647, 649, 651, and 653. In particular embodiments, any of the disclosed nucleic acid molecules encoding an N-terminal portion of a nucleobase editor fused at its C-terminus to an intein-N may comprise a nucleotide sequence that comprises any one of the sequences of SEQ ID NOs: 643, 645, 647, 649, 651, and 653.
In some embodiments, the disclosure provides compositions comprising a first nucleic acid molecule encoding a C-terminal portion of a nucleobase editor fused at its N-terminus to an intein-C that comprises a nucleotide sequence that is at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the nucleotide sequences of SEQ ID NOs: 642, 644, 646, 648, 650, and 652; and a second nucleic acid molecule encoding a C-terminal portion of a nucleobase editor fused at its N-terminus to an intein-C that comprises a nucleotide sequence that is at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to any one of the nucleotide sequences of SEQ ID NOs: 643, 645, 647, 649, 651, and 653. In particular embodiments, the compositions comprise a first nucleic acid molecule that comprises any one of the nucleotide sequences of SEQ ID NOs: 642, 644, 646, 648, 650, and 652, and a second nucleic acid molecule that comprises any one of the nucleotide sequences of SEQ ID NOs: 643, 645, 647, 649, 651, and 653. The disclosure also provides rAAV particles comprising any of the first nucleic acid molecules and second nucleic acid molecules described herein.
In some embodiments, the rAAV vector comprises: (1) a heterologous nucleic acid region comprising the first or second nucleotide sequence encoding the N-terminal portion or C-terminal portion of a split Cas9 protein or a split nucleobase editor in any form as described herein, (2) one or more nucleotide sequences comprising a sequence that facilitates expression of the heterologous nucleic acid region (e.g., a promoter), and (3) one or more nucleic acid regions comprising a sequence that facilitate integration of the heterologous nucleic acid region (optionally with the one or more nucleic acid regions comprising a sequence that facilitates expression) into the genome of a cell. In some embodiments, viral sequences that facilitate integration comprise Inverted Terminal Repeat (ITR) sequences. In some embodiments, the first or second nucleotide sequence encoding the N-terminal portion or C-terminal portion of a split Cas9 protein or a split nucleobase editor is flanked on each side by an ITR sequence. In some embodiments, the nucleic acid vector further comprises a region encoding an AAV Rep protein as described herein, either contained within the region flanked by ITRs or outside the region. The ITR sequences can be derived from any AAV serotype (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10) or can be derived from more than one serotype. In some embodiments, the ITR sequences are derived from AAV2, AAV8, AAV9, or AAV6.
Thus, in some embodiments, the rAAV particles disclosed herein comprise at least one rAAV2 particle, rAAV6 particle, rAAV8 particle, rPHP.B particle, rPHP.eB particle, or rAAV9 particle, or a variant thereof. In particular embodiments, the disclosed rAAV particles are rPHP.B particles, rPHP.eB particles, rAAV9 particles.
ITR sequences and plasmids containing ITR sequences are known in the art and commercially available (see, e.g., products and services available from Vector Biolabs, Philadelphia, Pa.; Cellbiolabs, San Diego, Calif.; Agilent Technologies, Santa Clara, Ca; and Addgene, Cambridge, Mass.; and Gene delivery to skeletal muscle results in sustained expression and systemic delivery of a therapeutic protein. Kessler P D, Podsakoff G M, Chen X, McQuiston S A, Colosi P C, Matelis L A, Kurtzman G J, Byrne B J. Proc Natl Acad Sci USA. 1996 Nov. 26; 93(24):14082-7; and Curtis A. Machida. Methods in Molecular Medicine™. Viral Vectors for Gene Therapy Methods and Protocols. 10.1385/1-59259-304-6:201 © Humana Press Inc. 2003. Chapter 10. Targeted Integration by Adeno-Associated Virus. Matthew D. Weitzman, Samuel M. Young Jr., Toni Cathomen and Richard Jude Samulski; U.S. Pat. Nos. 5,139,941 and 5,962,313, all of which are incorporated herein by reference). Exemplary ITR sequences are provided below.
In some embodiments, the rAAV vector of the present disclosure comprises one or more regulatory elements to control the expression of the heterologous nucleic acid region (e.g., promoters, transcriptional terminators, and/or other regulatory elements). In some embodiments, the first and/or second nucleotide sequence is operably linked to one or more (e.g., 1, 2, 3, 4, 5, or more) transcriptional terminators. Non-limiting examples of transcriptional terminators that may be used in accordance with the present disclosure include transcription terminators of the bovine growth hormone gene (bGH), human growth hormone gene (hGH), SV40, CW3, ϕ, or combinations thereof. The efficiencies of several transcriptional terminators have been tested to determine their respective effects in the expression level of the split Cas9 protein or the split nucleobase editor (e.g., see
In some embodiments, the composition comprising the rAAV particle (in any form contemplated herein) further comprises a pharmaceutically acceptable carrier. In some embodiments, the composition is formulated in appropriate pharmaceutical vehicles for administration to human or animal subjects.
Some examples of materials which can serve as pharmaceutically-acceptable carriers include: (1) sugars, such as lactose, glucose and sucrose; (2) starches, such as corn starch and potato starch; (3) cellulose, and its derivatives, such as sodium carboxymethyl cellulose, methylcellulose, ethyl cellulose, microcrystalline cellulose and cellulose acetate; (4) powdered tragacanth; (5) malt; (6) gelatin; (7) lubricating agents, such as magnesium stearate, sodium lauryl sulfate and talc; (8) excipients, such as cocoa butter and suppository waxes; (9) oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; (10) glycols, such as propylene glycol; (11) polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol (PEG); (12) esters, such as ethyl oleate and ethyl laurate; (13) agar; (14) buffering agents, such as magnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer's solution; (19) ethyl alcohol; (20) pH buffered solutions; (21) polyesters, polycarbonates and/or polyanhydrides; (22) bulking agents, such as polypeptides and amino acids (23) serum component, such as serum albumin, HDL and LDL; (22) C2-C12 alcohols, such as ethanol; and (23) other non-toxic compatible substances employed in pharmaceutical formulations. Wetting agents, coloring agents, release agents, coating agents, sweetening agents, flavoring agents, perfuming agents, preservative and antioxidants can also be present in the formulation. The terms such as “excipient”, “carrier”, “pharmaceutically acceptable carrier” or the like are used interchangeably herein.
Other aspects of the present disclosure provide methods of delivering the split Cas9 protein or the split nucleobase editor into a cell to form a complete and functional Cas9 protein or nucleobase editor. For example, in some embodiments, a cell is contacted with a composition described herein (e.g., compositions comprising nucleotide sequences encoding the split Cas9 or the split nucleobase editor or AAV particles containing nucleic acid vectors comprising such nucleotide sequences). In some embodiments, the contacting results in the delivery of such nucleotide sequences into a cell, wherein the N-terminal portion of the Cas9 protein or the nucleobase editor and the C-terminal portion of the Cas9 protein or the nucleobase editor are expressed in the cell and are joined to form a complete Cas9 protein or a complete nucleobase editor.
It should be appreciated that any rAAV particle, nucleic acid molecule or composition provided herein may be introduced into the cell in any suitable way, either stably or transiently. In some embodiments, the disclosed proteins may be transfected into the cell. In some embodiments, the cell may be transduced or transfected with a nucleic acid molecule. For example, a cell may be transduced (e.g., with a virus encoding a split protein), or transfected (e.g., with a plasmid encoding a split protein) with a nucleic acid molecule that encodes a split protein, or an rAAV particle containing a viral genome encoding one or more nucleic acid molecules. Such transduction may be a stable or transient transduction. In some embodiments, cells expressing a split protein or containing a split protein may be transduced or transfected with one or more guide RNA sequences, for example in delivery of a split Cas9 (e.g., nCas9) protein. In some embodiments, a plasmid expressing a split protein may be introduced into cells through electroporation, transient (e.g., lipofection) and stable genome integration (e.g., nucleofection or piggybac) and viral transduction or other methods known to those of skill in the art.
In some aspects, the invention provides methods comprising delivering one or more base editor-encoding polynucleotides, one or more transcripts thereof, and/or one or proteins transcribed therefrom, to a cell using a non-viral delivery method. Methods of non-viral delivery of nucleic acids include lipofection, nucleofection, microinjection, biolistics, virosomes, liposomes, immunoliposomes, polycation or lipid:nucleic acid conjugates, naked DNA, artificial virions, and agent-enhanced uptake of DNA. Lipofection is described in e.g., U.S. Pat. Nos. 5,049,386, 4,946,787; and 4,897,355) and lipofection reagents are sold commercially (e.g., Transfectam™ and Lipofectin™). Cationic and neutral lipids that are suitable for efficient receptor-recognition lipofection of polynucleotides include those of Feigner, WO 1991/17424; WO 1991/16024. Delivery can be to cells (e.g. in vitro or ex vivo administration) or target tissues (e.g. in vivo administration).
In certain embodiments, the compositions provided herein comprise a lipid and/or polymer. In certain embodiments, the lipid and/or polymer is cationic. The preparation of such lipid particles is well known. See, e.g. U.S. Pat. Nos. 4,880,635; 4,906,477; 4,911,928; 4,917,951; 4,920,016; 4,921,757; and 9,737,604, each of which is incorporated herein by reference.
In some embodiments, the target nucleotide sequence is a DNA sequence in a genome, e.g. a eukaryotic genome. In certain embodiments, the target nucleotide sequence is in a mammalian (e.g. a human) genome.
The target nucleotide sequence may comprise a target sequence (e.g., a point mutation) associated with a disease, disorder, or condition. The target sequence may comprise a T to C (or A to G) point mutation associated with a disease, disorder, or condition, and wherein the deamination of the mutant C base results in mismatch repair-mediated correction to a sequence that is not associated with a disease, disorder, or condition. The target sequence may otherwise comprise a G to A (or C to T) point mutation associated with a disease, disorder, or condition, and wherein the deamination of the mutant A base results in mismatch repair-mediated correction to a sequence that is not associated with a disease, disorder, or condition. The target sequence may encode a protein, and where the point mutation is in a codon and results in a change in the amino acid encoded by the mutant codon as compared to a wild-type codon. The target sequence may also be at a splice site, and the point mutation results in a change in the splicing of an mRNA transcript as compared to a wild-type transcript. In addition, the target may be at a non-coding sequence of a gene, such as a promoter, and the point mutation results in increased or decreased expression of the gene.
Thus, in some aspects, the deamination of a mutant C results in a change of the amino acid encoded by the mutant codon, which in some cases can result in the expression of a wild-type amino acid. In other aspects, the deamination of a mutant A results in a change of the amino acid encoded by the mutant codon, which in some cases can result in the expression of a wild-type amino acid.
The methods described herein involving contacting a cell with a composition or rAAV particle can occur in vitro, ex vivo, or in vivo. In certain embodiments, the step of contacting occurs in a subject. In certain embodiments, the subject has been diagnosed with a disease, disorder, or condition.
In some embodiments, the methods disclosed herein involve contacting a mammalian cell with a composition or rAAV particle. In particular embodiments, the methods involve contacting a retinal cell, cortical cell or cerebellar cell.
The split Cas9 protein or split nucleobase editor delivered using the methods described herein preferably have comparable activity compared to the original Cas9 protein or nucleobase editor (i.e., unsplit protein delivered to a cell or expressed in a cell as a whole). For example, the split Cas9 protein or split nucleobase editor retains at least 50% (e.g., at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 98%, at least 99%, or 100%) of the activity of the original Cas9 protein or nucleobase editor. In some embodiments, the split Cas9 protein or split nucleobase editor is more active (e.g., 2-fold, 5-fold, 10-fold, 100-fold, 1000-fold, or more) than that of an original Cas9 protein or nucleobase editor.
The compositions described herein may be administered to a subject in need thereof in a therapeutically effective amount to treat and/or prevent a disease or disorder the subject is suffering from. Any disease or disorder that maybe treated and/or prevented using CRISPR/Cas9-based genome-editing technology may be treated by the split Cas9 protein or the split nucleobase editor described herein. It is to be understood that, if the nucleotide sequences encoding the split Cas9 protein or the nucleobase editor does not further encode a gRNA, a separate nucleic acid vector encoding the gRNA may be administered together with the compositions described herein.
Exemplary suitable diseases, disorders or conditions include, without limitation the disease or disorder is selected from the group consisting of: cystic fibrosis, phenylketonuria, epidermolytic hyperkeratosis (EHK), chronic obstructive pulmonary disease (COPD), Charcot-Marie-Toot disease type 4J, neuroblastoma (NB), von Willebrand disease (vWD), myotonia congenital, hereditary renal amyloidosis, dilated cardiomyopathy, hereditary lymphedema, familial Alzheimer's disease, prion disease, chronic infantile neurologic cutaneous articular syndrome (CINCA), congenital deafness, Niemann-Pick disease type C (NPC) disease, and desmin-related myopathy (DRM). In particular embodiments, the disease or condition is Niemann-Pick disease type C (NPC) disease.
In some embodiments, the disease, disorder or condition is associated with a point mutation in an NPC1 gene, a DNMT1 gene, a PCSK9 gene, or a TMC1 gene. In certain embodiments, the point mutation is a T3182C mutation in NPC1, which results in an I1061T amino acid substitution.
In certain embodiments, the point mutation is an A545G mutation in TMC1, which results in a Y182C amino acid substitution. TMC1 encodes a protein that forms mechanosensitive ion channels in sensory hair cells of the inner ear and is required for normal auditory function. The Y182C amino acid substitution is associated with congenital deafness.
In some embodiments, the disease, disorder or condition is associated with a point mutation that generates a stop codon, for example, a premature stop codon within the coding region of a gene.
Additional exemplary diseases, disorders and conditions include cystic fibrosis (see, e.g., Schwank et al., Functional repair of CFTR by CRISPR/Cas9 in intestinal stem cell organoids of cystic fibrosis patients. Cell stem cell. 2013; 13: 653-658; and Wu et. al., Correction of a genetic disease in mouse via use of CRISPR-Cas9. Cell stem cell. 2013; 13: 659-662, neither of which uses a deaminase fusion protein to correct the genetic defect); phenylketonuria—e.g., phenylalanine to serine mutation at position 835 (mouse) or 240 (human) or a homologous residue in phenylalanine hydroxylase gene (T>C mutation)—see, e.g., McDonald et al., Genomics. 1997; 39:402-405; Bernard-Soulier syndrome (BSS)—e.g., phenylalanine to serine mutation at position 55 or a homologous residue, or cysteine to arginine at residue 24 or a homologous residue in the platelet membrane glycoprotein IX (T>C mutation)—see, e.g., Noris et al., British Journal of Haematology. 1997; 97: 312-320, and Ali et al., Hematol. 2014; 93: 381-384; epidermolytic hyperkeratosis (EHK)—e.g., leucine to proline mutation at position 160 or 161 (if counting the initiator methionine) or a homologous residue in keratin 1 (T>C mutation)—see, e.g., Chipev et al., Cell. 1992; 70: 821-828, see also accession number P04264 in the UNIPROT database at www[dot]uniprot[dot]org; chronic obstructive pulmonary disease (COPD)—e.g., leucine to proline mutation at position 54 or 55 (if counting the initiator methionine) or a homologous residue in the processed form of α1-antitrypsin or residue 78 in the unprocessed form or a homologous residue (T>C mutation)—see, e.g., Poller et al., Genomics. 1993; 17: 740-743, see also accession number P01011 in the UNIPROT database; Charcot-Marie-Toot disease type 4J—e.g., isoleucine to threonine mutation at position 41 or a homologous residue in
Suitable routes of administrating the composition for pain suppression include, without limitation: topical, subcutaneous, transdermal, intradermal, intralesional, intraarticular, intraperitoneal, intravesical, transmucosal, gingival, intradental, intracochlear, transtympanic, intraorgan, epidural, intrathecal, intramuscular, intravenous, intravascular, intraosseus, periocular, intratumoral, intracerebral, parenteral, and intracerebroventricular administration.
The compositions of this disclosure may be administered or packaged as a unit dose, for example. The term “unit dose” when used in reference to a pharmaceutical composition of the present disclosure refers to physically discrete units suitable as unitary dosage for the subject, each unit containing a predetermined quantity of active material calculated to produce the desired therapeutic effect in association with the required diluent, i.e., a carrier or vehicle.
Treatment of a disease or disorder includes delaying the development or progression of the disease, or reducing disease severity. Treating the disease does not necessarily require curative results.
As used therein, “delaying” the development of a disease means to defer, hinder, slow, retard, stabilize, and/or postpone progression of the disease. This delay can be of varying lengths of time, depending on the history of the disease and/or individuals being treated. A method that “delays” or alleviates the development of a disease, or delays the onset of the disease, is a method that reduces probability of developing one or more symptoms of the disease in a given time frame and/or reduces extent of the symptoms in a given time frame, when compared to not using the method. Such comparisons are typically based on clinical studies, using a number of subjects sufficient to give a statistically significant result.
“Development” or “progression” of a disease means initial manifestations and/or ensuing progression of the disease. Development of the disease can be detectable and assessed using standard clinical techniques as well known in the art. However, development also refers to progression that may be undetectable. For purpose of this disclosure, development or progression refers to the biological course of the symptoms. “Development” includes occurrence, recurrence, and onset.
As used herein “onset” or “occurrence” of a disease includes initial onset and/or recurrence. Conventional methods, known to those of ordinary skill in the art of medicine, can be used to administer the isolated polypeptide or pharmaceutical composition to the subject, depending upon the type of disease to be treated or the site of the disease.
In some aspects, the present disclosure provides uses of any one of the split nucleobase editors described herein and a guide RNA targeting this nucleobase editor to a target in the manufacture of a medicament. In some aspects, uses of any one of the nucleobase editors and guide RNAs described herein are provided in the manufacture of a kit for base editing, wherein the base editing comprises contacting the nucleic acid molecule with the split nucleobase editor and guide RNA under conditions suitable for the substitution of the adenine (A) of a A:T nucleobase pair in the target with a guanine (G), or for the substitution of the cytosine (C) of a C:T nucleobase pair in the target with a thymine (T). In some embodiments, the step of contacting of induces separation of the double-stranded DNA at a target region. In some embodiments, the step of contacting further comprises nicking one strand of the double-stranded DNA, wherein the one strand comprises an unmutated strand.
In some embodiments of the described uses, the step of contacting is performed in vitro. In other embodiments, the step of contacting is performed in vivo. In some embodiments, the step of contacting is performed in a subject (e.g., a human subject or a non-human animal subject). In some embodiments, the step of contacting is performed in a cell, such as a human or non-human animal cell.
The present disclosure also provides uses of any one of the nucleobase editors or any one of the complexes of nucleobase editors and guide RNAs described herein as a medicament. The present disclosure also provides uses of the described pharmaceutical compositions or cells comprising, and vectors or rAAV particles encoding, any of the disclosed nucleobase editors or complexes herein as a medicament. In particular embodiments, the medicament is for treatment of Niemann-Pick disease type C (NPC) disease, congenital deafness, or hearing loss.
The compositions of the present disclosure may be assembled into kits. In some embodiments, the kit comprises nucleic acid vectors for the expression of the nucleobase editors described herein. In some embodiments, the kit further comprises appropriate guide nucleotide sequences (e.g., gRNAs) or nucleic acid vectors for the expression of such guide nucleotide sequences, to target the Cas9 protein or nucleobase editor to the desired target sequence.
The kit described herein may include one or more containers housing components for performing the methods described herein and optionally instructions for use. Any of the kit described herein may further comprise components needed for performing the assay methods. Each component of the kits, where applicable, may be provided in liquid form (e.g., in solution) or in solid form, (e.g., a dry powder). In certain cases, some of the components may be reconstitutable or otherwise processible (e.g., to an active form), for example, by the addition of a suitable solvent or other species (for example, water), which may or may not be provided with the kit.
In some embodiments, the kits may optionally include instructions and/or promotion for use of the components provided. As used herein, “instructions” can define a component of instruction and/or promotion, and typically involve written instructions on or associated with packaging of the disclosure. Instructions also can include any oral or electronic instructions provided in any manner such that a user will clearly recognize that the instructions are to be associated with the kit, for example, audiovisual (e.g., videotape, DVD, etc.), Internet, and/or web-based communications, etc. The written instructions may be in a form prescribed by a governmental agency regulating the manufacture, use, or sale of pharmaceuticals or biological products, which can also reflect approval by the agency of manufacture, use or sale for animal administration. As used herein, “promoted” includes all methods of doing business including methods of education, hospital and other clinical instruction, scientific inquiry, drug discovery or development, academic research, pharmaceutical industry activity including pharmaceutical sales, and any advertising or other promotional activity including written, oral and electronic communication of any form, associated with the disclosure. Additionally, the kits may include other components depending on the specific application, as described herein.
The kits may contain any one or more of the components described herein in one or more containers. The components may be prepared sterilely, packaged in a syringe and shipped refrigerated. Alternatively it may be housed in a vial or other container for storage. A second container may have other components prepared sterilely. Alternatively the kits may include the active agents premixed and shipped in a vial, tube, or other container.
The kits may have a variety of forms, such as a blister pouch, a shrink wrapped pouch, a vacuum sealable pouch, a sealable thermoformed tray, or a similar pouch or tray form, with the accessories loosely packed within the pouch, one or more tubes, containers, a box or a bag. The kits may be sterilized after the accessories are added, thereby allowing the individual accessories in the container to be otherwise unwrapped. The kits can be sterilized using any appropriate sterilization techniques, such as radiation sterilization, heat sterilization, or other sterilization methods known in the art. The kits may also include other components, depending on the specific application, for example, containers, cell media, salts, buffers, reagents, syringes, needles, a fabric, such as gauze, for applying or removing a disinfecting agent, disposable gloves, a support for the agents prior to administration, etc.
Cells that may contain any of the compositions described herein include prokaryotic cells and eukaryotic cells. The methods described herein are used to deliver a Cas9 protein or a nucleobase editor into a eukaryotic cell (e.g., a mammalian cell, such as a human cell). In some embodiments, the cell is in vitro (e.g., cultured cell. In some embodiments, the cell is in vivo (e.g., in a subject such as a human subject). In some embodiments, the cell is ex vivo (e.g., isolated from a subject and may be administered back to the same or a different subject).
Mammalian cells of the present disclosure include human cells, primate cells (e.g., vero cells), rat cells (e.g., GH3 cells, OC23 cells) or mouse cells (e.g., MC3T3 cells). There are a variety of human cell lines, including, without limitation, human embryonic kidney (HEK) cells, HeLa cells, cancer cells from the National Cancer Institute's 60 cancer cell lines (NCI60), DU145 (prostate cancer) cells, Lncap (prostate cancer) cells, MCF-7 (breast cancer) cells, MDA-MB-438 (breast cancer) cells, PC3 (prostate cancer) cells, T47D (breast cancer) cells, THP-1 (acute myeloid leukemia) cells, U87 (glioblastoma) cells, SHSY5Y human neuroblastoma cells (cloned from a myeloma) and Saos-2 (bone cancer) cells. In some embodiments, rAAV vectors are delivered into human embryonic kidney (HEK) cells (e.g., HEK 293 or HEK 293T cells). In some embodiments, rAAV vectors are delivered into stem cells (e.g., human stem cells) such as, for example, pluripotent stem cells (e.g., human pluripotent stem cells including human induced pluripotent stem cells (hiPSCs)). A stem cell refers to a cell with the ability to divide for indefinite periods in culture and to give rise to specialized cells. A pluripotent stem cell refers to a type of stem cell that is capable of differentiating into all tissues of an organism, but not alone capable of sustaining full organismal development. A human induced pluripotent stem cell refers to a somatic (e.g., mature or adult) cell that has been reprogrammed to an embryonic stem cell-like state by being forced to express genes and factors important for maintaining the defining properties of embryonic stem cells (see, e.g., Takahashi and Yamanaka, Cell 126 (4): 663-76, 2006, incorporated by reference herein). Human induced pluripotent stem cell cells express stem cell markers and are capable of generating cells characteristic of all three germ layers (ectoderm, endoderm, mesoderm).
Additional non-limiting examples of cell lines that may be used in accordance with the present disclosure include 293-T, 293-T, 3T3, 4T1, 721, 9L, A-549, A172, A20, A253, A2780, A2780ADR, A2780cis, A431, ALC, B16, B35, BCP-1, BEAS-2B, bEnd.3, BHK-21, BR 293, BxPC3, C2C12, C3H-10T1/2, C6, C6/36, Cal-27, CGR8, CHO, CML T1, CMT, COR-L23, COR-L23/5010, COR-L23/CPR, COR-L23/R23, COS-7, COV-434, CT26, D17, DH82, DU145, DuCaP, E14Tg2a, EL4, EM2, EM3, EMT6/AR1, EMT6/AR10.0, FM3, H1299, H69, HB54, HB55, HCA2, Hepa1c1c7, High Five cells, HL-60, HMEC, HT-29, HUVEC, J558L cells, Jurkat, JY cells, K562 cells, KCL22, KG1, Ku812, KYO1, LNCap, Ma-Mel 1, 2, 3 . . . 48, MC-38, MCF-10A, MCF-7, MDA-MB-231, MDA-MB-435, MDA-MB-468, MDCK II, MG63, MONO-MAC 6, MOR/0.2R, MRCS, MTD-1A, MyEnd, NALM-1, NCI-H69/CPR, NCI-H69/LX10, NCI-H69/LX20, NCI-H69/LX4, NIH-3T3, NW-145, OPCN/OPCT Peer, PNT-1A/PNT 2, PTK2, Raji, RBL cells, RenCa, RIN-5F, RMA/RMAS, S2, Saos-2 cells, Sf21, Sf9, SiHa, SKBR3, SKOV-3, T-47D, T2, T84, THP1, U373, U87, U937, VCaP, WM39, WT-49, X63, YAC-1 and YAR cells.
Without further elaboration, it is believed that one skilled in the art can, based on the above description, utilize the present disclosure to its fullest extent. The following specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. All publications cited herein are incorporated by reference for the purposes or subject matter referenced herein.
In order that the invention described herein may be more fully understood, the following examples are set forth. The synthetic examples described in this application are offered to illustrate the compounds and methods provided herein and are not to be construed in any way as limiting their scope.
This study was designed to show that a nucleobase editor may be delivered by recombinant AAV (rAAV) in two sections, which may be joined to form a complete and active nucleobase editor in cells via protein splicing. Different elements of the rAAV constructs were tested for optimized nucleobase editor expression and activity.
Recombinant AAV (rAAV) is widely used for transgene delivery. Transgenes were inserted into the AAV genome between the inverted terminal repeat (ITR) sequences and packaged into AAV viral particles, which are used to transduce a host cell (e.g., mammalian cell, human cell). However, there is a limitation on the size of the transgene that may be packaged into rAAV, typically approximately 4.9 kilobases. Nucleic acids encoding a nucleobase editor (e.g., cytosine deaminase-dCas9-UGI) typically exceed the packaging limit of rAAV. As described herein, the nucleic acids encoding a nucleobase editor were split (see
Different transcriptional terminators and nuclear localization signals (NLS) were tested in the rAAV constructs to optimize the expression and activity of the nucleobase editors (see
This study was designed to test the base editing activity of an AAV encoded split nucleobase editor in vivo. A split nucleobase editor as shown in
In one experiment, AAV vectors encoding the split nucleobase editor and a guide RNA targeting DNMT1 were used to transduce dissociated mouse cortical neurons, two days after the cortical neurons were isolated and cultured. The neurons were harvested 16 days post transduction and the DNMT1 gene was sequenced (
In another experiment, cultured mouse Neuro-2 cells were either transduced with AAV vectors encoding the split nucleobase editor and a guide RNA targeting DNMT1, or transfected with lipid-encapsulated DNA encoding the nucleobase editor and guide RNA, allowing direct comparison of editing efficiency using different delivery methods of the nucleobase editor (
It was reasoned that the use of a trans-splicing intein would enable CBE and ABE to be divided into halves that are each smaller than the AAV packaging size limit, enabling dual AAV packaging of nucleobase editors (
After identifying a BE3 split site that does not impair base editing efficiencies following intein splicing, split-intein CBE performance was optimized. The performance of the Npu split intein was compared with that of Cfa, a synthetic split intein developed from the consensus sequences of fast-splicing DnaE homologs from a variety of organisms20. Npu-BE3 outperformed Cfa-BE3, which resulted in 25±10% average base editing (
Using the Cys 574 Cas9 split site and the Npu split intein, a split optimized adenine nucleobase editor (Npu-ABEmax) construct was also generated that reconstitutes ABEmax6 activity to edit a test site in the mouse DNMT1 gene (63±5.4% A.T-to-G.C editing from Npu-ABEmax, compared to 63±6.3% editing from non-split ABEmax,
After developing a viable way to divide both classes of nucleobase editors into split intein-fused halves, a series of AAV particles was generated and characterized to optimize base editing efficiency and minimize AAV genome size to support efficient AAV production23. Several post-transcriptional regulatory element sequences (PREs) and sgRNA positions were tested in the context of AAV, rather than plasmid delivery, to maximize the in vivo relevance of the optimization process.
To avoid effects specific to cultured cells, PHP.B24 was used, which is an evolved AAV variant that efficiently crosses the blood-brain barrier in mice, to test PRE variants in the mouse CNS. 1×1011 vg of PHP.B-CMV-eGFP-NLS was delivered into 8-week-old mice by retro-orbital injection, and harvested brain tissue for imaging after a 3-week incubation. W3, a truncated Woodchuck hepatitis virus PRE (WPRE) sequence25, increased PHP.B-delivered GFP-NLS expression levels in the brain ˜19-fold compared to no regulatory sequence (
Although the tendency of the CMV promoter to be silenced over time in vivo may be beneficial for some genome editing applications by minimizing off-target editing opportunities19,26,27, silencing was avoided to maximize editing efficiency in this initial study. The Cbh promoter is a ubiquitous, constitutive promoter that is less sensitive to silencing in vivo than the CMV promoter28. Exemplary nucleobase editor AAV constructs therefore contained the W3 sequence, Npu intein, and Cbh promoter, which is referred to hereafter as v3 AAV. To optimize split-base editor AAV configurations, murine 3T3 cells were transduced with dual v3 AAV-PHP.B encoding split-CBE3.9 and a validated sgRNA targeting the mouse DNMT1 locus29. DNMT1 acts redundantly with DNMT3a in the mammalian brain30 and is therefore well-suited for proof-of-concept studies. A dose of 2×1011 viral genomes (vg) of v3 AAV per well of 50,000 NIH 3T3 cells, using a 1:1 ratio of the two AAVs, resulted in 14±4.8% C.G-to-T.A editing at the DNMT1 locus. NLS- and codon-optimized CBE3.9max constructs, termed v4 AAV-CBE3.9max, improved C.G-to-T.A editing efficiency to 37±18%, a 2.6-fold increase relative to unoptimized v3 AAV CBE3.9 (
After optimizing PRE, promoter, NLS, and codon usage, the impact of different guide RNA placements and orientations were tested within the AAV genome. Guide RNA transcription efficiency is known to be sensitive to proximity and orientation relative to AAV ITRs31. Moving the U6-sgRNA cassette to the 3′ end of the viral genome and reversing its orientation31, yielding v5 AAV, improved C.G-to-T.A editing efficiency a further 1.5-fold relative to v4 AAV, for a total 3.9-fold total improvement compared to the initial v3 AAV constructs (56±12% for v5 AAV-CBE3.9max versus 14±4.8% for v3 AAV-CBE3.9). These transduction experiments were repeated at a lower virus dose, 2×1010 vg per well, and observed 14-fold higher C.G-to-T.A editing efficiency for v5 AAV compared to v3 AAV, and 5.6-fold higher editing for v5 AAV compared to v4 AAV (1.7±0.73% for v3 AAV-CBE3.9, 4.1±2.2% for v4 AAV-CBE3.9max, and 23±5.2% for v5 AAV-CBE3.9max) (
Next the performance of the optimized AAV split-intein nucleobase editor constructs was characterized in vivo. AAV9 is reported to transduce tissues including liver, skeletal muscle, heart, and CNS32-34. Dual AAV9 particles were generated in the v5 AAV architecture encoding the optimized split CBE3.9max (
A recent study by Ryu, Kim and coworkers reported AAV-mediated delivery of ABE split by trans-mRNA splicing8. The rAAV constructs reported in Ryu et al.8 were modified to enable direct comparison by replacing the muscle-specific Spc5-12 promoter with the Cbh promoter for ubiquitous expression, and replacing the DMD-targeting sgRNA with the DNMT1-targeting sgRNA. To directly compare the efficiency of AAV-delivered nucleobase editors reconstituted through split intein-mediated splicing, versus trans-mRNA splicing, trans-mRNA splicing constructs were generated with the DNMT1-targeting sgRNA and Cbh promoter. In side-by-side comparisons measuring base editing in three tissues, split intein-spliced v5 AAV ABE on average provided 4.5-fold higher base editing efficiencies than trans-RNA-spliced ABE (
Notably, base editing efficiencies in heart and skeletal muscle from split-intein AAV9 constructs (
Recently, Villiger et al. developed an intein-split S. aureus CBE (see Villiger, L. et al. Nature Medicine 24, 1519-1525 (2018), incorporated herein by reference). To compare those constructs to the v5 constructs described herein, a v5 S. aureus CBE using intein-split SaBE3.9max was generated, which has the same NLS- and codon optimizations as the S. pyogenes Npu-BE3.9max construct, and was cloned into the v5 AAV architecture. Then, dual AAV genomes in AAV8 were packaged with an sgRNA designed to generate the PCSK9 W8X mutation31, 3-week-old mice were injected either 1×1011 or 1×1012 total vg per animal retro-orbitally, and liver tissue was harvested for high-throughput sequencing 4 weeks after injection. The Villiger constructs were modified only by replacement of the liver-specific P3 promoter with Cbh, and the Pah-targeting guide with PCKS9 W8X. At the higher dose, the constructs performed comparably (v5 AAV saCBE: 20±0.9% W8X-encoding alleles; Villiger saCBE: 18±1.6% W8X-encoding alleles). At the lower dose, however, no reduction in editing by the v5 AAV saCBE constructs (25±6.0% W8X alleles) was observed, but a substantial reduction in the editing efficiency of the Villiger constructs (8.2±3.2% W8X alleles) (
The above results establish an in vivo CBE and ABE delivery solution for somatic tissues transduced following systemic AAV injection. Delivery to the central nervous system (CNS), however, is especially challenging. Although AAV9 has been reported45 to cross the blood-brain barrier and transduce CNS cells, minimal editing was observed in the brain following adult retro-orbital injection (
For all CNS delivery experiments, dual split-intein CBE or ABE v5 AAV targeting DNMT1 were combined together with an AAV encoding a Cbh promoter-driven nuclear membrane-localized GFP-KASH29 fusion to enable FACS isolation of cells with GFP-positive nuclei. Sorting for GFP-positive cells enriches cell types that are transducible by AAV and that can transcribe genes from the Cbh promoter. This enrichment is especially useful in the CNS, where the heterogeneity of interspersed cell types limits enrichment from physical dissection alone. For example, in the cerebellum, only Purkinje cells, comprising less than 1% of total cerebellar tissue50,51, are well-transduced by known AAV variants at P052,53. These neurons, however, are critically important as their degeneration causes a number of cerebellar ataxias54,55. FACS isolation facilitates quantification of editing in this sparse population, as shown by comparison of editing among sorted and unsorted cell populations (
To determine optimal AAV variants for P0 ICV injections, 4×1010 vg total of v5 CBE AAV was co-injected with 1×1010 vg of KASH-GFP (
Next, cerebellar and cortical tissue were sequenced. In cortex, it was found that all four tested AAV variants mediated comparable and efficient C.G-to-T.A base editing among GFP-positive cells (65-70% base editing), as well as among unsorted cells (32-50% base editing) (
Having demonstrated cytosine base editing in the brain with v5 AAV-CBE3.9max, adenine base editing was tested with v5 AAV-delivered ABEmax. Since all AAV variants tested produced similar CBE3.9max base editing efficiencies, P0 ICV injections of split-intein ABEmax were characterized using only AAV9. It was observed that AAV9-delivered split-intein ABEmax edited cortex with high efficiency (87±4.0% A.T-to-G.C editing among GFP-positive cells; 43±9.1% editing among unsorted cells) and cerebellum (64±5.6% among GFP-positive cells; 1.3±0.5% among unsorted cells, consistent with the small percentage of Purkinje neurons in cerebellum) (
Although direct CNS injections resulted in robust base editing in the brain, it was also sought to determine whether peripheral delivery of AAV via intravenous injection might efficiently edit the CNS, since intravenous injections offer substantial convenience, cost, and safety advantages. 4×1012 vg of v5 AAV-PHP.eB encoding CBE3.9max mixed with 2×1011 vg GFP-KASH were injected retro-orbitally into nine-week old animals (
Genome editing approaches to treating inherited ocular disorders are of special interest given the accessibility of the eye, its immune-privileged status, and the prevalence and impact of congenital blindness. Therefore, the ability of subretinal injections of split-intein ABEmax v5 AAV or split-intein CBE3.9max v5 AAV to efficiently base edit photoreceptors and other retinal cells was tested. Rhodopsin-Cre mice, which express Cre only in retinal rod photoreceptor cells, were bred to Ai9 mice57 to generate animals that express tdTomato only in rod photoreceptor cells. Subretinal injections of split-intein CBE3.9max or ABEmax dual AAV were performed, targeting DNMT1 in two-week old mice (
Three weeks post-injection, retinal cells were sorted into GFP+/tdTomato+ (transduced rods), GFP+/tdTomato− (marker transduced non-rods), GFP−/tdTomato+ (unmarked rods), or double-negative (unmarked non-rods) cells. PHP.B-GFP transduced 65±2.8% of rods and 9.6±1.4% of non-rods, while a 6-fold lower dose of Anc80-GFP transduced cells much less efficiently (
Interestingly, although ABE delivery generated very few indels in retinal cells, consistent with previous results from cultured cells4, and both ABE and CBE delivery in non-retinal tissues in the experiments described above generally resulted in base edit:indel ratios >10:1 (
Integrating the above developments, AAV-mediated in vivo nucleobase editor delivery was applied to correct a mutation associated with human disease in the CNS of an animal. NPC1 mediates intracellular lipid transport, and loss-of-function mutations cause Niemann-Pick type C (NPC) disease, a neurodegenerative ataxia. NPC1 c.3182T>C (encoding Ile1061Thr) is the most prevalent mutation in humans that causes NPC1 disease61,62. Previous work suggests that Niemann-Pick disease is primarily a CNS disorder; genetic deletion of NPC1 in the CNS alone causes Niemann-Pick disease in mice63, while expression of wild-type NPC1 in the CNS alone prevents the disease64,65. Furthermore, deletion of NPC1 in Purkinje cells alone causes motor impairment66. Chimeric studies suggest that the death of Purkinje neurons is cell-autonomous and therefore amenable to mosaic rescue67. NPC1I1061T homozygous mice develop ataxia and have a reduced lifespan of approximately 17 weeks62.
To test if base editing of NPC1I1061T in the CNS might extend lifespan, P0 NPC1I1061T (c.3182T>C) homozygous mice were injected with 4×1010 or 1×1011 vg total CBE3.9max v5 AAV9 (2×1010 or 5×1010 vg of each AAV half) targeting the NPC1I1061T mutation and 1×1010 vg of KASH-GFP, which are referred to as low dose and medium dose, respectively. Base editing at this site should directly reverse the I1061T mutation back to wild-type NPC1 (
To determine if v5 AAV9-CBE injection increases the number of surviving Purkinje neurons, a cohort of age-matched injected and untreated mice were compared at P98-P105, close to the lifespan of the untreated mice. In agreement with the observed lifespan extension, injection of AAV9 AAV-CBE increases the number of surviving Purkinje neurons, from 24% of wild-type to 38% of wild-type (uninjected, 5.1±1.2 Purkinje neurons per mm of Purkinje cell layer; injected, 8.0±0.8 PCs/mm; wild-type, 21.1±5.5 PCs/mm; uninjected vs. injected, p=0.03) (
In animals given a low dose of v5 AAV, the NPC1I1061T mutation was corrected with 31±16% efficiency in unsorted cortical nuclei, and in 46±22% of GFP-positive nuclei. In cerebellum, editing of 0.4±0.5% was observed in unsorted tissue, and 11±8.4% in GFP-positive nuclei, which correspond to the critical Purkinje neuron population that must be edited to treat NPC1 disease. In medium-dose animals, cortical editing of 48±8.2% and 81±3.7% was observed in unsorted and sorted nuclei, respectively, and cerebellar editing of 0.3±0.2% and 42±14% of unsorted and sorted nuclei, respectively (
It was also determined whether off-target editing might occur in the sorted cerebellar and cortical nuclei. Candidate loci were identified using two methods: one method was utilizing CRISPOR, a bioinformatics method to predict off-target sites with Cas9 activity, and the second method was empirically determining off-target Cas9 loci using CIRCLE-seq on gDNA harvested from the liver of an untreated NPC1I1061T mouse. Amplicon sequencing was then performed to confirm editing at eight total candidate loci identified by either method. Only a single confirmed off-target site was observed, an intronic sequence in Epas1>3 kb away from the nearest exonic sequences, which was edited at a low efficiency of 0.3±0.05% (
Previous work with mosaic animals' has shown that approximately 30-40% wild-type cells are required for measurable phenotypic improvement. Since the above data suggest ˜11% Purkinje cell editing in low-dose animals with no lifespan extension, and ˜42% Purkinje cell editing in medium-dose animals with modest but significant lifespan extension, the results broadly agree with the modest lifespan gains observed in mosaic animal studies67. It is noted that unedited cells may have degenerated, and thus editing levels in sequenced tissue represent upper limits of the initial percentage of edited cells. To minimize the effect of degeneration on the frequency of edited cells, base editing was measured in heterozygous NPC1I1061T/+ mice, which do not show NPC1 disease phenotypes, following medium-dose P0 injections. At P29, it was found that 31±5.8% of GFP-positive cerebellar nuclei were edited, which increased to 54±10% at P110. In sorted cortical nuclei, the percent of edited cells increased from 59±5.4% to 82±7.2% (
To test whether CBE is chronically expressed, NPC1+/+ mice were injected with v5 AAV-CBE at P0 and brains were harvested at P110 for staining against Cas9 and GFP. Expression of both Cas9 and GFP was observed at P110 in cerebellar and cortical tissue (
These results establish that dual AAV split-intein nucleobase editor delivery in Niemann-Pick type C mice directly corrects a substantial fraction of pathogenic alleles in the CNS. Together, these results demonstrate for the first time base editing to treat an animal model of a human CNS disease, correcting the causal mutation and prolonging lifespan.
This study describes an optimized dual AAV system that delivers split-intein cytosine and adenine nucleobase editors, resulting in therapeutically relevant in vivo genome editing efficiencies following injection of ˜1013-1014 vg/kg, a dosage comparable to those currently used in human gene therapy trials32. The optimizations described above greatly improve the efficiency of AAV-encoded nucleobase editors and may also be useful to other AAV-based systems for the delivery of genome editing agents8,22. Many somatic cell types of therapeutic and scientific interest can be efficiently transduced with known AAV variants, including hematopoetic cells68, liver69, sensory organs11, and CNS32, suggesting that this work may facilitate a broad range of studies in animal models of many human genetic diseases. Finally, different injection routes were tested to deliver AAV-packaged split-base editors in postnatal mice and demonstrate, for the first time, efficient base editing in brain and retina, enabling causal gene correction and partial phenotypic rescue of Niemann-Pick type C disease.
The mouse studies described here use AAV injections of no more than 4×1012 vg per 20-g animal, which corresponds to a maximum dose of 2×1014 vg/kg, consistent with the maximum dosages delivered intravenously in non-human primate studies' and clinical trials32 for CNS delivery. Notably, in the eye, subretinal injections of the optimized nucleobase editor AAVs achieve genome editing efficiencies comparable to those of preclinical delivery systems optimized for retinal editing60. Intravenous v5 AAV injections also achieve therapeutically relevant editing levels in liver, muscle, and cardiac tissue. The viral base editing systems developed in this study therefore are suitable for testing base editing strategies in animal models of human disease, a key step in advancing base editing towards human therapeutic application. AAV optimization (
While it was initially anticipated that the requirement of simultaneous transduction by two viruses would sharply lower editing efficiencies, the surprisingly high overall in vivo editing efficiencies observed even among unsorted cells (for example, up to 59% of cortex), together with similar levels of transduction of single AAVs expressing GFP (
The split-intein nucleobase editor delivery system developed here brings the strengths of base editing, including high editing efficiency, minimization of unwanted byproducts arising from double-stranded DNA breaks, and compatibility with post-mitotic somatic cells2,9, to in vivo settings in the diverse tissue types that are well-transduced by natural or engineered AAVs. The split-intein dual AAV approach described here may also facilitate the in vivo delivery of genes that are too large for a direct gene augmentation approach.
HEK239T/17 (ATCC CRL-11268) and 3T3 cells (ATCC CRL-1658) were maintained in DMEM (Thermo Fisher 10569044) supplemented with 10% (v/v) fetal bovine serum (Thermo Fisher), at 37° C. with 5% CO2. Cells were verified to be free of mycoplasma by ATCC upon purchase, and periodically during culture.
HEK293T cells were seeded into 48-well Poly-D-Lysine-coated plates (Corning 354509) at 30,000 cells/well. One day after plating, cells were transfected by Lipofectamine 2000 (Thermo Fisher) according to the manufacturer's directions with 1 μg DNA in a 1:1 molar ratio of nucleobase editor and sgRNA plasmids, plus 10 ng of fluorescent protein expression plasmid as a transfection control. Cells were cultured for 3 days before genomic DNA was extracted by replacement of culture media with 100 μL lysis buffer (10 mM Tris-HCl, pH 7.5, 0.05% SDS, 25 μg/mL proteinase K (NEB) and 37° C. incubation for 1 hour. Proteinase K was inactivated by 30-minute incubation at 80° C. 3T3 cells were transfected using the same procedure at 50,000 cells/well.
HEK293T cells were seeded into 12-well plates at 125,000 cells per well. Cells were transfected as described above with all amounts scaled up 3x. For conditions with transfection of only one split-half, EGFP-expressing plasmid was used to normalize the amount of DNA used. 3 days after transfection, cells were gently lifted and triturated by pipetting PBS across the well surface. 10% of the volume was removed for HTS analysis, and the remaining cells were washed with ice-cold PBS, and incubated on ice for 15 minutes in lysis buffer (300 mM NaCl, 50 mM Tris pH 8, 1% IGEPAL 0.5% deoxycholic acid, 10 mM MgCl) plus 25 U/mL salt active nuclease (Arcticzymes 70910-202) to reduce lysate viscosity and complete EDTA-free protease inhibitor cocktail (Roche). After 10 minutes, SDS and EDTA were added to 0.5% and 1 mM, respectively, and lysates were rocked an additional 15 minutes at 4° C. before clarification by centrifugation at 14,000 g for 15 minutes at 4° C. Lysates were normalized using BCA (Pierce BCA Protein Assay Kit), and 2.5 mg of reduced protein was loaded onto each gel lane. Transfer was performed with an iBlot 2 dry blotting system (Thermo Fisher) using the following program: 20 V for 1 minute, then 23 V for 4 minutes, then 25 V for 2 minutes for a total transfer time of 7 minutes. Blocking was performed at room temperature for 30 minutes with block buffer: 1% BSA in TBST (150 mM NaCl, 0.5% Tween-20, 50 mM Tris-Cl, pH 7.5). Membranes were then incubated in primary antibody diluted in block buffer at 4° C. overnight. After a wash step, secondary antibodies diluted in TBST were added. Membranes were washed again and imaged using a LI-COR Odyssey. Wash. steps were 3×5 minute washes in TBST. Primary antibodies used were rabbit anti-GAPDH, 1:1000 (Cell Signaling Technologies D16H11); rabbit anti-HA, 1:1000 (Cell Signaling Technologies C29F4), mouse anti-FLAG 1 μg/mL (clone M2, Sigma F1804). LI-COR IRDye 680RD goat anti-rabbit (#926-68071) and goat antimouse (#926-68070) secondary antibodies were used at 1:10,000-1:20,000 dilutions.
Genomic DNA was amplified by qPCR using Phusion Hot Start II DNA polymerase with use of SYBR gold for quantification. 3% DMSO was added to all gDNA PCR reactions. To minimize PCR bias, reactions were stopped during the exponential amplification phase. 1 uL of the unpurified gDNA PCR product was used as a template for subsequent barcoding PCR (8 cycles, annealing temperature 61° C.). Pooled barcoding PCR products were gel-extracted (Min-elute columns, Qiagen) and quantified by qPCR (KAPA KK4824) or Qubit dsDNA HS assay kit (Thermo Fisher). Sequencing of pooled amplicons was performed using an Illumina MiSeq according to the manufacturer's instructions. All oligonucleotide sequences used for gDNA amplification are provided in
Initial de-multiplexing and FASTQ generation were performed by bcl2fastq2 running on BaseSpace (Illumina) with the following flags: --ignore-missing-bcls --ignore-missing-filter --ignore-missing-positions --ignore-missing-controls --auto-set-to-zero-barcode-mismatches -- find-adapters-with-sliding-window --adapter-stringency 0.9--mask-short-adapter-reads 35--minimum-trimmed-read-length 35. Alignment of fastq files and quantification of editing frequency was performed by CRISPResso2 in batch mode with the following flags: --min_bp_quality_or_N 20--base_editor_output -p 2-w 20-wc -10.
AAV production was performed as previously described24 with some alterations. HEK293T/17 cells were maintained in DMEM/10% FBS without antibiotic in 150 mm dishes (Thermo Fisher 157150), and passaged every 2-3 days. Cells for production were split 1:3 1 day before PEI transfection. 5.7 μg AAV genome, 11.4 μg pHelper (Clontech), and 22.8 μg rep-cap plasmid were transfected per plate. 1 day after transfection, media was exchanged for DMEM/5% FBS. 3 days after transfection, cells were scraped with a rubber cell scraper (Corning), pelleted by centrifugation for 10 minutes at 2000 g, resuspended in 500 μL hypertonic lysis buffer per plate (40 mM Tris base, 500 mM NaCl, 2 mM MgCl2 with 100 U/mL salt active nuclease (Arcticzymes 70910-202), and incubated at 37° C. for 1 h to lyse cells.
Media was decanted, combined with a 5× solution of 40% PEG in 2.5 M NaCl (final concentration 8% PEG/500 mM NaCl), incubated on ice for 2 hours to facilitate PEG precipitation, and centrifuged at 3200 g for 40 minutes. The supernatant was discarded and the pellet resuspended in 500 μL lysis buffer per plate and added to the cell lysate. Incubation at 37° C. was continued for 30 minutes. Crude lysates were either incubated at 4° C. overnight or directly used for ultracentrifugation.
Cell lysates were gently clarified by centrifugation at 2000 g for 10 minutes and added to Beckman Quick-seal tubes via 16-gauge 5″ disposable needles (Air-Tite N165). A discontinuous iodixanol gradient was formed by sequentially floating layers: 9 mL 15% iodixanol in 500 mM NaCl and 1×PBS-MK (1×PBS plus 1 mM MgCl2 and 2.5 mM KCl), 6 mL 25% iodixanol in 1×PBS-MK, and 5 mL each of 40% and 60% iodixanol in 1×PBS-MK. Phenol red at a final concentration of 1 μg/mL was added to the 15, 25, and 60% layers to facilitate identification.
Ultracentrifugation was performed using a Ti 70 rotor in a Sorvall WX+ series ultracentrifuge (Thermo Fisher) at 58,600 rpm for 2:15 (h:mm) at 18° C. Following ultracentrifugation, roughly 4 mL of solution was withdrawn from the 40%-60% iodixanol interface via an 18-gauge needle, dialyzed with PBS containing 0.001% F-68, and ultrafiltered via 100-kD MWCO columns (EMD Millipore). The concentrated viral solution was sterile-filtered using a 0.22 μm filter, quantified via qPCR (AAVpro Titration Kit v.2, Clontech), and stored at 4° C. until use.
All experiments in live animals were approved by the Broad Institute and Massachusetts Eye and Ear Institutional and Animal Care and Use Committees. NPC1 mice were euthanized at the onset of morbidity, defined as profound ataxia leading to an inability to acquire food and water, as evidenced by a low body condition score and minimal responsiveness to touch. Wild-type C57BL/6 mice were from Charles River (#027). Jackson Labs supplied all transgenic mice: Npc1tm(I1061T)Dso (#027704), Ai9 (#007909), Rhodopsin-iCre (#015850), and L7-GFP (#004690).
AAV was diluted to 200 μL in 0.9% NaCl (Fresenius Kabi 918610) before injection. Anesthesia was induced with 4% isoflurane. Following induction as measured by unresponsiveness to a toe pinch, the right eye was protruded by gentle pressure on the skin, and a tuberculin syringe advanced, with the bevel facing away from the eye, into the retrobulbar sinus where AAV mix was slowly injected. For assessments of CNS editing, 1×1011 vg GFP-KASH virus was added to the injection mix as a transduction marker. gDNA was purified from minced tissue using Agencourt DNAdvance kits (Beckman Coulter A48705) in accordance with the manufacturer's directions.
Drummond PCR pipettes (5-000-1001-X10) were pulled at ramp and passed through a Kimwipe three times, resulting in a tip size roughly 100 μm. A small amount of Fast Green was added to the AAV injection solution to assess ventricle targeting. The injection solution was loaded via front-filling using the included Drummond plungers. P0 pups were anesthetized by placement on ice for 2-3 minutes, until they were immobile and unresponsive to a toe pinch. 2 μL of injection mix was injected freehand into each ventricle. Ventricle targeting was assessed by the spread of fast green throughout the ventricles via transillumination of the head.
Cerebella were separated from the brain with surgical scissors, hemispheres were separated using a scalpel, and the hippocampus and neocortex were separated from underlying midbrain tissue with a curved spatula. Nuclei were isolated from brain tissue as previously described72. All steps were performed on ice or at 4° C. Dissected tissue was homogenized using a glass dounce homogenizer (Sigma D8938) (20 strokes with pestle A followed by 20 strokes with pestle B) in 2 mL ice-cold EZ-PREP buffer (Sigma NUC-101). Samples were incubated for 5 minutes with an additional 2 mL EZ-PREP buffer. Nuclei were centrifuged at 500 g for 5 minutes, and the supernatant removed. Samples were resuspended with gentle pipetting in 4 mL ice-cold Nuclei Suspension Buffer (NSB) consisting of 100 μg/mL BSA and 3.33 μM Vybrant DyeCycle Violet (Thermo Fisher) in 1×PBS, and centrifuged at 500 g for 5 minutes. The supernatant was removed and nuclei were resuspended in 1-2 mL NSB, passed through a 35 μm strainer, and sorted into 200 μL Agencourt DNAdvance lysis buffer using a MoFlo Astrios (Beckman Coulter) at the Broad Institute flow cytometry core. Genomic DNA was purified according to the Agencourt DNAdvance instructions for 200 μL volume.
1 μL of AAV mix for sub-retinal injections consisted of 4×109 vg of each split CBE nucleobase editor half, and 2×109 vg GFP for the PHP.B variant. The Anc80+CBE3.9max mixture was divided equally: 3.3×108 vg of each split nucleobase editor half, and 3.3×108 vg GFP. The Anc80+ABEmax mixture consisted of 4.5×108 vg of each split nucleobase editor half, and 4.5×108 vg GFP. PHP.B or Anc80 GFP alone at 5×109 vg/μL was injected into wild-type C57BL/6 mice to assess transduction efficiency. P14 mice were anesthetized by intraperitoneal of ketamine (140 mg/kg) and xylazine (14 mg/kg). Using a microscope for visualization, a small incision was made at the limbus by a 30-gauge needle, and a Hamilton syringe with a 33-gauge blunt-ended needle was used to inject 1 μL of AAV mix. Following injection, mice were placed on a 37° C. warming pad until they recovered.
Three weeks post-injection, eyes were enucleated and stored in BGJB medium (Thermo Fisher) on ice as described previously73. Retinas were isolated under a fluorescent dissection microscope to record the transfected region and dissociated into single cells by incubation in solution A containing 1 mg/mL pronase (Sigma-Aldrich) and 2 mM EGTA in BGJB medium at 37° C. for 20 minutes. Solution A was gently removed, followed by adding equal amount of solution B containing 100 U/mL DNase I (New England Biolabs), 0.5% BSA, 2 mM EGTA in BGJB medium. Cells were collected and re-suspended in 1×PBS, filtered through a cell strainer (BD Biosciences, San Jose, Calif.), and sorted using a FACSAriaII (BD Biosciences).
Mice injected with PHP.B or Anc80 GFP alone were sacrificed 3 weeks post-injection and perfused with 4% paraformaldehyde in 1×PBS. Eyes were dissected and eye cups were embedded in OCT freezing medium. 10 μm Retinal cryosections were cut and stained with DAPI. Images were taken using an Eclipse Ti microscope (Nikon).
Mice were transcardially perfused with PBS followed by 4% PFA. Harvested brains were rotated in 4% PFA at 4° C. overnight for post-fixation. Brains were transferred to 30% sucrose in 1×PBS for cryoprotection and rotated at 4° C. until equilibrated, as assessed by loss of buoyancy. Cryoprotected brains were frozen in a dry ice-ethanol bath and sectioned horizontally on a Leica CM1950 at 20 p.m. Slides were rinsed with 10 mM glycine in PBS before blocking and permeabilization in 3% BSA (Jackson Immunoresearch) and 0.1% Trition-X 100 in PBS. Slides were incubated in primary antibody at 4° C. overnight, washed three times for 10 minutes each with PBS containing 0.1% Triton-X (PBSTx), incubated with secondary antibody at room temperature for 1 hour, washed 3×10 minutes with PBSTx, and mounted in ProLong Diamond Antifade with DAPI (Thermo Fisher). Slides were cured overnight at room temperature before imaging. Care was taken to minimize light exposure at all steps. Primary antibodies used were as follows: chicken anti-GFP, 10 μg/mL (Abcam ab13970); rabbit anti-RFP, 1.6 μg/mL (Rockland 600-401-379); rabbit anti-Calbindin, 0.1 μg/mL. (Cell Signaling Technology D1I4Q). Alexa-conjugated goat secondary antibodies (Thermo Fisher) were used at 1:500. Images were captured and stitched at 10× magnification using a Zeiss Axio Scan.Z1. Image intensity was kept below 50% saturation to prevent oversaturation.
Images were analyzed using ImageJ (Fiji), ilastik74, and CellProfiler75. A subset of images were manually analyzed by a blinded experimenter to validate the accuracy of the final imaging pipelines. Differences between the automated and manual counts were <10%.
CIRCLE-seq was performed as previously described76. PCR amplification before sequencing was conducted using PhusionU polymerase, and products were gel-purified and quantified with a KAPA library quantification kit before loading onto an Illumina MiSeq. Data was processed using the CIRCLE-Seq analysis pipeline with parameters: “read_threshold: 4; window_size: 3; mapq_threshold: 50; start_threshold: 1; gap_threshold: 3; mismatch_threshold: 6; merged_analysis: True”. The three sites found by CIRCLE-seq analysis were chosen for PCR amplification and high-throughput sequencing. CRISPOR analysis77 was done and the top five offtarget candidates by CFD score were analyzed by amplicon sequencing.
NPC1I1061T Survival Measurements
NPC1I1061T mice were euthanized at the onset of morbidity, defined functionally as profound ataxia leading to an inability to acquire food and water, as evidenced by a low body condition score78,79 and minimal responsiveness to touch. In all cases, low body condition score preceded profound ataxia. Profound ataxia was the diagnostic criterion for morbundity. The endpoint was designed to minimize suffering while providing accurate survival data. Euthanasia recommendations were made by a blinded veterinary technician. All survival groups were mixed-gender.
The logrank (Mantel-Cox) test was used to compare Kaplan-Meier survival curves (GraphPad).
Key plasmids from this work are available from Addgene (depositor: David R. Liu) and other plasmids are available upon request. All unmodified reads for sequencing-based data in the manuscript are available from the NCBI Sequence Read Archive, accession number PRJNA532891. AAV genome sequences are provided as
16 Zetsche, B., Volz, S. E. & Zhang, F. A split-Cas9 architecture for inducible genome editing and transcription modulation. Nature biotechnology 33, 139-142, doi:10.1038/nbt.3149 (2015).
Sensory hair cells of Baringo mice have a complete loss of auditory sensory transduction and thus are profoundly deaf. The Baringo (Tmc1Y182C/Y182C; Tmc2+/+) mouse model is homozygous for a recessive loss-of-function T.A-to-C.G mutation in Tmc1 (c.A545G) that substitutes Tyr 182 for Cys (p.Y182C), results in profound deafness by 4 weeks of age. TMC1 protein is required for proper sensory transduction in hair cells of the cochlea. To repair the p.Y182C mutation several optimized cytidine nucleobase editors (CBEmax variants) and guide RNAs were tested in Baringo mouse embryonic fibroblasts. The most promising CBE, derived from an activation-induced cytosine deaminase (AID), was packaged into dual AAV vectors using a split-intein system. The dual AID-CBEmax AAVs were injected into the inner ears of Baringo mice at postnatal day 1 (P1). Injected mice showed up to 51% correction of the c.A545G point mutation in Tmc1 transcripts, which restored the wild-type Tmc1 coding sequence (c.A545A) in sensory hair cells of the inner ear. Repair of Tmc1 in vivo rescued hair-cell sensory transduction, hair-cell morphology, and substantial low-frequency hearing four weeks post-injection.
To develop a base editing strategy capable of correcting the Baringo mutation (Tmc1 c.A545G), protospacer sequences at the target site were searched. Three protospacer-adjacent motifs (PAMs) were identified that allow binding of S. pyogenes Cas9 (SpCas9, AGG PAM) or the engineered VRQR SpCas9 variant (GGA or TGA PAM) to the target locus in a manner that positions the target Tmc1 nucleotide within or near the cytosine base editing activity window (approximately protospacer positions 4-8, counting the PAM as positions 21-23). Three candidate guide RNAs position this target C:G base pair at protospacer position 8 (sgRNA1, AGG PAM), position 7 (sgRNA2, GGA PAM), or position 10 (sgRNA3, TGA PAM) (
Potential bystander edits near the target nucleotide in Tmc1, which is located in the sequence 5′ . . . AACAGGAAGACGAGGCCAC . . . 3′ (SEQ ID NO: 513), were considered. When the target nucleotide is at protospacer position 8 (C8), no other C nucleotides lie within the canonical CBE activity window (18). The closest bystander C, at protospacer position 10, if edited to a T would result in a silent mutation, because both TCG and TCA on the opposite DNA strand encode Serine. The nearest non-silent Cs are located at C−8 and C15, well outside the base editing activity window when using any of the three candidate sgRNAs described above (
The target Tmc1 nucleotide is in an AG sequence context. It was previously noted that APOBEC1-derived CBEs (including the commonly used BE3 and BE4 variants), edit G
targets less efficiently, consistent with the known DNA sequence preferences of APOBEC1 deaminase. In contrast with APOBEC1, the CDA1 deaminase from P. marinus, and human AID deaminase both deaminate G
substrates efficiently. To compare the activity of CDA1- and AID-derived nucleobase editors at the Baringo mutation site, nuclear localization-optimized, codon-optimized BE4max (also known as APOBEC1-BE4max) that replaces APOBEC1 with CDA1 (resulting in CDA1-BE4max) was constructed, with a highly active laboratory-evolved CDA1 variant recently described83 (resulting in evoCDA1-BE4max), or with human AID deaminase (resulting in AID-BE4max).
Next, cells from Baringo mouse embryos were isolated to compare the editing efficiency of APOBEC1-BE4max, CDA1-BE4max, evoCDA1-BE4max, and AID-BE4max for targeting Tmc1. Mouse embryonic fibroblasts (MEFs) were extracted from Baringo embryos at day 13.5. The ability of APOBEC1-BE4max, CDA1-BE4max, evoCDA1-BE4max, and AID-BE4max to convert the target Tmc1 base pair from pathogenic C:G to wildtype T:A using sgRNA1 was evaluated.
To minimize variability from nucleobase editor expression differences among cells, plasmids encoding each nucleobase editor as a P2A-GFP fusion were constructed and GFP-positive cells were analyzed by high-throughput DNA sequencing (HTS). Since P2A is a self-cleaving peptide that couples GFP production with full-length nucleobase editor translation, GFP-positive cells must also express nucleobase editor. Baringo MEF cells were nucleofected with two-plasmid mixtures in which one plasmid expressed sgRNA1 and the other expressed APOBEC1-BE4max-P2A-GFP, CDA1-BE4max-P2A-GFP, evoCDA1-BE4max-P2A-GFP, or AID-BE4max-P2A-GFP. After three days, the GFP-positive cells were isolated and sequenced.
As anticipated, APOBEC1-BE4max+sgRNA1 showed inefficient (mean±SEM of 2.0±0.7%) editing at G8, likely due to the disfavored sequence context of the target C. In contrast, CDA1-BE4max resulted in 12-fold improved target base editing efficiency (23±1.4%), AID-BE4max resulted in 21-fold more efficient editing (43±0.6%), and evoCDA1-BE4max resulted in 25-fold higher editing (50±2.8%), compared to APOBEC1-BE4max (
Subsequently, the effect of varying the position of the Baringo mutation among sgRNA1, sgRNA2, and sgRNA3, which place the target C at protospacer positions 8, 7, or 10, respectively, was tested (
To successfully prevent mutant Tmc1-mediated hearing loss using base editing, the nucleobase editor and guide RNA, or their encoding DNA, must be delivered into cochlear hair cells in the inner ear. Anc80L65, an ancestrally reconstructed AAV hereafter referred to as Anc80, was selected due to its demonstrated safety and efficacy in the mouse inner ear82. To validate the ability of Anc80 to deliver genes into inner hair cells (IHCs) and outer hair cells (OHCs) of Baringo mice, 7.2×108 vg of Anc80 AAV encoding GFP driven by the chicken (3-actin hybrid (Cbh) promoter was administered by intracochlear injection into the inner ear of P1 Baringo mice. This viral dose, corresponding to 1.8×109 vg/kg, is well within the range of AAV known to be tolerated in human retina in clinical applications. High viral transduction efficiency was observed in MC (41.7% in apex and 22.6% in base of cochlea) and low transduction in OHC (8.3% in apex and 2.6% in base of cochlea) (
Since the coding sequence of nucleobase editors (˜5.2 kB) exceeds the DNA capacity of AAVs, AID-BE4max was modified in two ways to enable AAV-mediated delivery. First, the nucleobase editor was divided into two halves (an N-terminal half and a C-terminal half) between Glu573 and Cys574, and fused each nucleobase editor half with one half of the Npu trans-splicing split intein. Co-expression of both nucleobase editor-intein halves results in rapid protein splicing, reconstituting full-length nucleobase editor. Second, the second uracil glycosylase inhibitor (UGI) domain was removed in each, yielding AID-BE3.9max. It was recently shown that removing the second UGI copy in split-intein CBE variants minimally affects base editing efficiency. These two changes enabled the nucleobase editor along with sgRNA1 and all necessary promoter and regulatory sequences to fit within two AAVs (≤4,849 bp each).
To test whether this split-intein dual AAV strategy mediated efficient base editing of Tmc1, Baringo MEF cells were transduced with dual AAVs encoding AID-BE3.9max+gRNA1 at two dosages. The high dose of the N-terminus half was 6.1×108 vg and the low dose was 3.1×107 vg; the high dose of the C-terminus half was 8.3×108 vg and the low dose was 4.2×107 vg. After applying the dual AAV encoding AID-BE3.9max+sgRNA1 to MEF cells, cells were cultured for two weeks before analyzing editing outcomes using HTS (
Next, base editing at off-target genomic loci bound by the Cas9:sgRNA1 complex was investigated. Previous reports using unbiased genome-wide off-target detection methods for nucleobase editors have observed that off-target substrates of nucleobase editors are generally a subset of off-targets for the corresponding Cas9 nuclease. CIRCLE-seq, a current unbiased, sensitive, cell-free off-target detection protocol, was used to identify potential off-target editing sites associated with Cas9 and sgRNA1. Genomic DNA was extracted and fragmented from Baringo MEFs, the ˜500-bp DNA fragments were ligated into circles, and Cas9 was incubated with sgRNA1. After Cas9 incubation, the cut circles were ligated to adaptors and identified the location of DNA cleavage events by HTS (
Then, amplicon sequencing was performed to measure base editing at the ten genomic sites with the largest number of CIRCLE-seq reads, including the on-target site and the top nine off-target sites (
Characterizing Sensory Transduction Currents in Tmc1Y182C/Y182C; Tmc2Δ/Δ mice
While the Tmc1 Y182C mutation is known to cause deafness in Baringo (Tmc1Y182C/Y182C; Tmc2+/+) mice by 4 weeks of age, the consequence of this mutation on hair cell function has not been previously reported. To determine the effect of the Baringo mutation on sensory transduction currents, the cochlea from Baringo mice was dissected at P8 and recorded currents from the sensory hair cells on the same day of dissection. Robust hair-cell current amplitudes were observed (
Based on previous reports, it was hypothesized that the robust currents in P8 mice were the result of transient expression of Tmc2, which encodes transmembrane channel-like 2 and is redundant with Tmc1 in neonatal mice (P8 or younger). To isolate the consequences of the Y182C substitution on transduction current, Baringo mice were crossed with Tmc2 knockout mice to generate Tmc1Y182C/Y182C; Tmc2Δ/Δ mice. Hair cells from Tmc1Y182C/Y182C; Tmc2Δ/Δ mice lacked sensory transduction currents entirely (
After establishing that AAV-mediated base editing can directly correct the Tmc1Y182C/Y182C mutation in cultured Baringo MEF cells (
To more directly assess the base editing efficiency of hair cells within organ of Corti samples, cochlear Tmc1 mRNA of treated mice was sequenced by reverse transcription of total mRNA and amplicon sequencing using primers specific to Tmc1. Given that Tmc1 in the cochlea is only expressed among hair cells, base-edited Tmc1 cDNA observed in the cochlea likely reflects base editing of hair cells. Indeed, 10 to 51% editing efficiency of Tmc1 mRNA was observed, which is 5- to 25-fold higher than DNA editing levels measured in bulk organ of Corti tissue (
Inner and outer hair cells of Baringo mice begin to die around four weeks of age, progressing from the base of the cochlea toward the apex. To investigate the ability of AAV delivered AID-BE3.9max+sgRNA1 to preserve hair cells and hair bundle morphology, Baringo mice were injected at P1, euthanized at P28, and inner ear was excised tissue for histological examination. No overt evidence of inflammation or tissue damage was observed in any of the injected ears. Cochleas were harvested and the entire organ of Corti was dissected, mounted and stained. Given the lack of high-quality anti-TMC1 antibody to visualize TMC1 directly, an anti-Myo7A antibody stain was used to label surviving hair cells. Confocal microscopy analysis of the immunostained organ of Corti tissue revealed no significant differences in overall OHC or IHC survival between untreated and treated Baringo mice (
Hair bundle morphology was observed using scanning electron microscopy (SEM). High resolution SEM images revealed striking morphological differences between treated and untreated Baringo hair bundles, particularly in the cochlear apex. Baringo mice injected with AAV-AID-BE3.9max+sgRNA1 had both IHC and OHC bundles from the apical end of the cochlea with morphologies more similar to those of wild-type mice than untreated Baringo mice (
After establishing that AAV-mediated base editing can directly correct the Tmc1Y182C/Y182C mutation in cultured Baringo MEF cells (
A FM1-43 uptake was imaged in two groups of Tmc1Y182C/Y182C; Tmc2Δ/Δ mice: an untreated control group, and a treated group that received an intracochlear injection of 1 μL of 7.2×108 vg total of dual AAV encoding AID-BE3.9max+sgRNA1 at P1. After 5-7 days of treatment, the cochlea from both groups of mice was dissected (Tmc1Y182C/Y182C; Tmc2Δ/Δ), the cochleas were cultured in vitro for 7-10 days, and FM1-43 was applied. No FM1-43 uptake in the IHCs or OHCs of untreated mice was observed, but robust FM1-43 uptake among 75±10% (n=4 cochleas) of IHCs of treated mice, and very little FM1-43 uptake in OHCs of treated mice was observed (
To directly assess the effect of in vivo base editing on IHC function, sensory transduction currents from IHCs were recorded. 3.1×109 vg of each AAV encoding AID-BE3.9max+sgRNA1 was injected into the inner ear of P1 Tmc1Y182C/R182C; tmc2Δ/Δ mice and the organ of Corti was extracted at P5. Extracted P5 organ of Corti tissue was maintained in culture and incubated for an additional 7-10 days before cellular recording. In agreement with the FM1-43 uptake data (
Collectively, these results demonstrate that in vivo delivery of dual AAVs encoding AID-BE3.9max and sgRNA1 restored wild-type (
The rescue of IHC morphology and restoration of IHC sensory transduction in base-edited Baringo mice suggests that these mice may exhibit rescued cochlear function compared to untreated Baringo mice, which are profoundly deaf at 4 weeks of age. To test this possibility, auditory brainstem responses (ABRs) were measured at P30 in untreated Baringo mice and Baringo (Tmc1Y182C/Y182C; Tmc2+/+) mice injected at P1.
The ABR threshold is the lowest decibel (dB) level needed to generate identifiable auditory brainstem waveforms. Representative families of ABR waveforms recorded in response to 5.6-kHz tone bursts of varying sound intensity are illustrated in
A summary plot of ABR thresholds as a function of frequency for all four groups are illustrated in
The function of outer hair cells (OHCs) using distortion product otoacoustic emissions (DPOAE) were also measured (
Finally, to rule out any possible adverse effects of the injection procedure, AAV transduction, or post-splicing intein peptide in the ABR or DPOAE tests, AAV encoding AID-BE3.9max+sgRNA1 was injected into the inner ears of four wild-type mice (
Collectively, these results demonstrate that AAV-mediated base editing of Tmc1Y182C/Y182C improves auditory function in Baringo mice and represent the first in vivo rescue of a recessive sensory impairment disease by base editing.
Recessive loss-of-function mutations cause most known genetic hearing loss diseases. As described herein, base editing was used in vitro and in vivo to correct a point mutation in transmembrane channel-like 1 (Tmc1) that causes profound deafness. Base editing fully restored hair-cell function in a subset of cells, preserved hair-cell morphology, and rescued auditory sensitivity especially to low frequencies in a mouse model of human recessive deafness. These results represent the first correction (rather than disruption) of a pathogenic mutation in the inner ear resulting in improved auditory function and demonstrate the promise of base editing to directly correct loss-of-function recessive mutations. Among 108 recorded human Tmc1 mutations that likely cause genetic hearing loss, can, in principle, be corrected with cytosine or adenine nucleobase editors (Table 5). The focus of these Examples was on a recessive loss-of-function mutation; however, the nucleobase editors described herein may also be used to correct dominant mutations.
In vivo delivery of AAV encoding an optimized nucleobase editor and guide RNA resulted in up to 50% base editing efficiency in restoring the wild-type coding sequence of Tmc1 in hair cells (HCs) in Baringo mice. Importantly, base-edited hair cells were mostly IHCs, which upon treatment resisted morphological degeneration normally seen in untreated Baringo mice. The treated mice also exhibited normal sensory transduction currents, unlike IHCs of untreated Baringo mice. Treated mice exhibited ABR thresholds at 5.6 kHz improved by at least 10-50 dB compared to the undetectable ABR thresholds observed in untreated Baringo mice. Given that the untreated Baringo mouse model used herein has no detectable auditory function at 4 weeks of age, this level of auditory function rescue represents a major improvement. For a patient with a similar loss-of-function TMC1 mutation, a corresponding improvement would represent the difference between hearing nothing at all to being able to detect salient auditory cues in the environment, such as alarms, ringing phones, or sirens from an emergency vehicle. Moreover, this level of auditory function could be supplemented with hearing aids that extend auditory functional recovery.
To rescue auditory sensitivity over a greater range of frequencies, it will be necessary to develop a similarly efficient base editing delivery strategy for editing outer hair cells (OHCs). The development of viral capsids or promoters capable of supporting dual OHC transduction with higher efficiency thus holds promise to further improve outcomes of correcting mutations that cause genetic hearing loss. In addition, the onset of degeneration at the basal (high-frequency) end of the cochlea is thought to occur earlier than at the apical (low-frequency) end, suggesting the importance of treating as early as possible to rescue high-frequency auditory function.
The methods described herein aimed to use base editing in the post-natal mouse inner ear to correct a recessive loss-of-function point mutation that causes congenital deafness, resulting in the rescue of hair-cell sensory transduction, hair-cell morphology, and auditory function. nucleobase editor variants that correct a recessive mutation in Tmc1 were identified in cultured cells and in vivo. AAV vectors were used to deliver nucleobase editors in vitro and in vivo, and editing outcomes were evaluated using high-throughput sequencing, quantitative RT-PCR, immunolocalization and confocal microscopy, scanning electron microscopy, imaging of FM1-43 uptake, single-cell current transduction recording, histology and imaging of whole cochleas, and measurement of ABR and DPOAE thresholds. Left ears were injected and right ears were used as uninjected controls. Each experiment was replicated as indicated by n values in the figure legends. All experiments with mice and viral vectors were approved by the Institutional Animal Care and Use Committee (Protocols #17-03-3396R and 18-01-3610R) at Boston Children's Hospital and the Institutional Biosafety Committee.
Wild-type mice were C57BL/6J (Jackson Laboratories). Two genotypes of mutant mice were used: Tmc1Y182C/Y182C; Tmc2+/+ and Tmc1Y182C/Y182C; Tmc2Δ/Δ. The Tmc1p.Y182C “Baringo” mice were obtained from Murdoch Children's Research Institute (The Royal Children's Hospital, Australia). Mice with genotype Tmc1Y182C/Y182C; Tmc2Δ/Δ were obtained by crossing of Tmc1Δ/Δ; Tmc2Δ/Δ with Tmc1Y182C/Y182C; Tmc2+/+. Mice that carried mutant alleles of Tmc1 and Tmc2 were on C57BL/6J or BALB/c backgrounds as described previously. Wild-type control mice were C57BL/6J (Jackson Laboratories). All procedures met the NIH guidelines for the care and use of laboratory animals and were approved by the Institutional Animal Care and Use Committees at Boston Children's Hospital (Protocols #17-03-3396R and 18-01-3610R). Mice ages P0-P1 were used for in vivo delivery of viral vectors according to protocols mentioned above. Mice were genotyped using toe clip (before P8) or ear punch (after P8) and PCR was performed as described previously. For all studies, both male and female mice were used in approximately equal proportions.
Baringo (Tmc1Y182C/Y182C; Tmc2+/+) Mouse Embryonic Fibroblast Cell Generation
Baringo females at 3-4 weeks of age were treated with single intra-peritoneal injection of 5 U each of pregnant mare's serum gonadotropin (Prospec) followed by human chorionic gonadotropin (Sigma) after 44-45 hours and paired with Baringo males. The following morning, females were examined for copulatory plugs to confirm matings and marked as 0.5 dpc. At day 13.5 females were sacrificed by CO2 inhalation followed by cervical dislocation. Embryos were harvested in PBS under aseptic conditions. To harvest primary embryonic fibroblasts, each embryo was eviscerated and head was removed. The remaining parts of each embryo were minced to prepare single-cell suspensions and treated with 0.25% Trypsin-EDTA (Gibco) at 37° C. for 10 minutes, followed by centrifugation for 10 minutes. Pellets were resuspended in growth media containing DMEM, 10% FBS, penicillin-streptomycin (100 U/mL) and plated on 15-cm tissue culture plates, then incubated at 37° C. until confluent. The Baringo colony is maintained ad libitum and all animal procedures are approved by the Children's Hospital IACUC in compliance with relevant ethical regulations.
Nucleofection and Viral Infection of Baringo (Tmc1Y182C/Y182C; Tmc2+/+) MEF Cells
MEF cells were cultivated until confluent, then pooled. Replicates were performed on the same day using three separate nucleofections followed by cultivation in separate wells. Each nucleofection contained 400 ng nucleobase editor as a P2A-GFP plasmid and 100 ng guide RNA plasmid. Transfection programs were optimized following manufacturer's instructions (CZ-167, P4 Primary Cell 4D-Nucleofector X Kit, Lonza). Cells were sorted at the MIT FACS core three days after nucleofection and genomic DNA was purified directly after sorting. Next, high-throughput DNA sequencing (HTS) was performed. For AAV infection, each AAV was added to a single well of a 48-well plate. After 2 weeks, the DNA was extracted and analyzed by HTS.
Genomic DNA was purified from sorted cells or cochlea tissue using Agencourt DNAdvance kits (Beckman Coulter A48705) following the manufacturer's directions.
RNA Isolation from the Cochlea
RNA isolation was performed with the RNeasy Plus Micro Kit (QIAGEN) according to the manufacturer's instructions. In brief, 250 μL of RLT Plus Buffer (QIAGEN) b-mercaptoethanol was added to each tube with one cochlea in it; tissue was homogenized by pipetting, fast freezing, and vertexing, and transferred into a DNA eliminator column. Subsequent binding and washing steps for RNA isolation using the RNeasy columns were performed according to the manufacturer's instructions. RNA was eluted from the RNeasy column with 45 μL of RNase-free water (QIAGEN). Total RNA was converted into cDNA on the same day.
cDNA Generation for Targeted RNA Amplicon Sequencing
cDNA was generated from the isolated RNA using the Prot® Script II First Strand cDNA Synthesis Kit (New England Biolabs) according to the manufacturer's instructions with Oligo-dT primers. Amplification of cDNA for high-throughput sequencing was performed to the top of the linear range (29 cycles) using qPCR as described below. High-throughput sequencing of amplicons was performed as described below. Sequences were aligned to the reference sequence for each RNA, obtained from the NCBI.
CIRCLE-seq was performed as previously described. PCR amplification before sequencing was conducted using PhusionU polymerase, and products were gel-purified and quantified with a KAPA library quantification kit before loading onto an Illumina MiSeq. Data was processed using the CIRCLE-Seq analysis pipeline with parameters: “read_threshold: 4; window_size: 3; mapq_threshold: 50; start_threshold: 1; gap_threshold: 3; mismatch_threshold: 6; merged_analysis: True”. The top ten most common sites based on CIRCLE-seq read count were chosen for PCR amplification and high-throughput sequencing.
Genomic DNA was amplified by qPCR using Q5 High-Fidelity 2× Master Mix with use of SYBR gold for quantification. To minimize PCR bias, reactions were stopped during the exponential amplification phase. 2 uL of the unpurified gDNA PCR product was used as a template for subsequent barcoding PCR (8 cycles, annealing temperature 61° C.). Pooled barcoding PCR products were gel-extracted (Min-elute columns, Qiagen) and quantified by qPCR (KAPA KK4824). Sequencing of pooled amplicons was performed using an Illumina MiSeq according to the manufacturer's instructions. All oligonucleotide sequences used for gDNA amplification are provided in Table 3.
Initial de-multiplexing and FASTQ generation were performed by bcl2fastq2 running on BaseSpace (Illumina) with the following flags: --ignore-missing-bcls --ignore-missing-filter --ignore-missing-positions --ignore-missing-controls --auto-set-to-zero-barcode-mismatches -- find-adapters-with-sliding-window --adapter-stringency 0.9--mask-short-adapter-reads 38--minimum-trimmed-read-length 38. Alignment of fastq files and quantification of editing frequency was performed by CRISPResso2 in batch mode with the following flags: --min_bp_quality_or_N 20--base_editor_output -p 2-w 20-wc -10.
For quantification of conversion to wild-type Tmc1 protein (
Temporal bones were harvested from mouse pups at P0-P5. Pups were euthanized by rapid decapitation and temporal bones were dissected in MEM (Invitrogen, Carlsbad, Calif.) supplemented with 10 mM HEPES, 0.05 mg/ml ampicillin, and 0.01 mg/ml ciprofloxacin at pH 7.4. The membranous labyrinth was isolated under a dissection scope, Reissner's membrane was peeled back, and the tectorial membrane and stria vascularis were mechanically removed. Organ of Corti cultures were pinned flatly beneath a pair of thin glass fibers adhered at one end with Sylgard to an 18-mm round glass coverslip. Tissues were either used acutely or kept in culture in presence of 1% Fetal Bovine Serum. Cultures were maintained for 7 to 10 days. For mice older than P10, temporal bones were harvested after euthanizing the animal with inhaled CO2, and cochlear whole mounts were generated.
Recordings were performed in standard artificial perilymph solution containing (in mM): 144 NaCl, 0.7 NaH2PO4, 5.8 KCl, 1.3 CaCl2, 0.9 MgCl2, 5.6 D-glucose, and 10 HEPES-NaOH, adjusted to pH 7.4 and 320 mOsmol/kg. Vitamins (1:50) and amino acids (1:100) were added from concentrates (Invitrogen, Carlsbad, Calif.). Hair cells were viewed from the apical surface using an upright Axioskop FS microscope (Zeiss, Oberkochen, Germany) equipped with a 63× water immersion objective with differential interference contrast optics. Recording pipettes (3-5 MΩ) were pulled from borosilicate capillary glass (Garner Glass, Claremont, Calif.) and filled with intracellular solution containing (in mM): 135 KCl, 5 EGTA-KOH, 10 HEPES, 2.5 K2ATP, 3.5 MgCl2, 0.1 CaCl2, pH 7.4. Currents were recorded under whole-cell voltage-clamp at a holding potential of −64 mV at room temperature. Data were acquired using an Axopatch 200A (Molecular devices, Palo Alto, Calif.) filtered at 10 kHz with a low pass Bessel filter, digitized at ≥20 kHz with a 12-bit acquisition board (Digidata 1322) and pClamp 8.2 and 10.5 (Molecular Devices, Palo Alto, Calif.). Data were analyzed offline with OriginLab software.
Anc80L65 vectors carrying the split coding sequences of AID-BE3.9max, inteins, sgRNA1, and Cbh promoter (a hybrid form of chicken (3-actin promoter) were generated using a helper virus free system and a double transfection method. All viruses were produced by the Viral Core at Boston Children's Hospital. Titers were calculated by qPCR with ITR primers (LITR-F: GACCTTTGGTCGCCCGGCCT (SEQ ID NO: 481); LITR-R: GAGTTGGCCACTCCCTCTCTGC (SEQ ID NO: 484)) and GFP primers (GFP-F: AGAACGGCATCAAGGTGAAC (SEQ ID NO: 485); GFP-R: GAACTCCAGCAGGACCATGT (SEQ ID NO: 486)). All three vectors were purified using an iodixanol step gradient followed by ion exchange chromatography. Virus aliquots were stored at −80° C. The titer was 6.11×1012 per mL for BE3.9max-AID-N-terminal and 8.26×1012 per mL for C-terminal virus.
FM1-43 (Invitrogen) was diluted in extracellular recording solution (5 μM final concentration) and applied to tissues for 10 seconds, then washed three times in extracellular recording solution to remove excess and prevent uptake via endocytosis. After 5 minutes the intracellular FM1-43 was imaged (Zeiss Axioscope FS Plus) using an FM1-43 filter set and epifluorescence light source with a 63× water immersion objective, or by confocal microscopy.
All injected and non-injected cochleae were harvested after animals were sacrificed by CO2 inhalation. Temporal bones were removed and immersion fixed for 1 hour at room temperature with 4% paraformaldehyde. Cochleae were then rinsed in PBS and stored at 4° C. in preparation for dissection and immunohistochemistry. Before dissection, temporal bones were decalcified in 120 mM EDTA for 24 h (for P30). For the subsequent immunohistochemical analysis, tissues were infiltrated with 0.01% Triton X-100 for 30 minutes and blocked in 2.5% normal goat serum (Jackson ImmunoResearch) and 2.5% bovine serum albumin (Jackson ImmunoResearch) diluted in PBS (blocking solution) for 1 h and subsequently stained with a rabbit anti-Myosin VIIa primary antibody (Proteus Biosciences, Product #: 25-6790, 1:500 dilution in blocking solution) at 4° C. overnight. A secondary antibody cocktail consisting of a mixture of donkey anti-rabbit antibody conjugated to AlexaFluor 555 (Life Technologies, 1:200 dilution (2 mg/mL)), AlexaFluor 555-phalloidin and AlexaFluor 647-phalloidin (Molecular Probes, 1:200 dilution (2 mg/mL)) as a counterstain to label filamentous actin was applied for 2 h. Samples were mounted on glass coverslips with Vectashield mounting medium (Vector Laboratories), and imaged at 10×-63× magnification using a Zeiss LSM800 confocal microscope. Three-dimensional projection images were generated from Z-stacks using ZenBlue (Zeiss).
SEM was performed at ˜P30 (4 weeks) along the organ of Corti of control and mutant mice. Organ of Corti explants were fixed in 2.5% glutaraldehyde in 0.1 M cacodylate buffer (Electron Microscopy Sciences) supplemented with 2 mM CaCl2 for 1 hour at room temperature. Specimens were dehydrated in a graded series of acetone (35%, 70%, 95%, and 100% (×2)), critical-point dried from liquid CO2, sputter-coated with 4-5 nm of platinum (Q150T, Quorum Technologies, United Kingdom), and observed with a field emission scanning electron microscope (S-4800, Hitachi, Japan).
ABR recordings were conducted from mice anesthetized via IP injection (0.1 mL/10 g-body weight) with 1 mL of ketamine (50 mg/mL) and 0.75 mL of xylazine (20 mg/mL). Subcutaneous needle electrodes were inserted into the skin (a) dorsally between the two ears (reference electrode); (b) behind the left pinna (recording electrode); and (c) dorsally at the rump of the animal (ground electrode). Prior to the onset of ABR testing, the meatus at the base of the pinna was trimmed away to expose the ear canal, and sound pressure at the entrance of the ear canal was calibrated for each individual test subject at all stimulus frequencies. For ABR recordings the ear canal and hearing apparatus (EPL Acoustic system, MEE, Boston) were presented with 5-millisecond tone pips. ABR potentials were amplified (10,000×), filtered (0.3-10 kHz), and digitized using custom data acquisition software (LabVIEW) from the Eaton-Peabody Laboratories Cochlear Function Test Suite. Sound level was raised in 5 to 10 dB steps from 0 to 110 dB sound pressure level (decibels SPL). At each level, 512 to 1024 responses were averaged (with stimulus polarity alternated) after “artifact rejection”. Threshold was determined by visual inspection. Data were analyzed and plotted using Origin-2015 (OriginLab Corporation, MA).
DPOAE data were collected under the same conditions, and during the same recording sessions, as ABR data. DPOAE at 2f1−f2 were measured with f2 frequencies from 5.6 to 45.2 kHz in half-octave steps (f2/f1=1.22) and L1−L2=10 dB SPL. At each f2, L2 was varied between 10 and 80 dB sound-pressure level (SPL) in 10 dB SPL increments. DPOAE threshold was defined from the average spectra as the L2-level eliciting a DPOAE of magnitude 5 dB SPL above the noise floor. The mean noise floor level was under 0 dB across all frequencies. Iso-response curves were interpolated from plots of DPOAE amplitude versus sound level. Threshold was defined as the f2 level required to produce DPOAEs above 0 dB.
Inner ear injections were performed as approved by the Institutional Animal Care and Use Committees at Boston Children's Hospital animal protocol #17-03-3396R and 18-01-3610R. Pups were anesthetized by rapid induction of hypothermia for 2-4 minutes on ice water until loss of consciousness, and this state was maintained on a cooling platform for 10-15 minutes during the surgery. Approximately 1 μL of dual AAV were injected in neonatal mice P0-P1. Upon anesthesia, post-auricular incision was made to expose the otic bulla and visualize the cochlea. Standard post-operative care was applied.
Statistical analyses were performed with Origin 2016 (OriginLab Corporation) or Prism 7. Data are presented as mean values ±standard deviations (SD) or standard error of the mean (SEM) as noted in the text and figure legend. Student's t-test was used to determine statistical significance (p-values). Error bars and n values of biological replicates for experiments are defined in the respective paragraphs and figure legends.
An example of the CRISPResso2 output from a single AID-BE4max-mediated base editing experiment is shown. The c.A545G mutation is in italics, silent bystander cytosines are bold, and the AGG PAM is underlined. The total conversion to sequences encoding wild-type TMC1 protein was 44%.
The ClinVar database was searched for pathogenic SNPs in TMC1. Of all 108 pathogenic mutations found in patients, 72 mutations are in principle reversible with CBE or ABE nucleobase editor.
Exemplary guide sequences (expressed as protospacer sequences) suitable for targeting the NPC1 genes and used in the experiments of Examples 1-4 are provided in Table 6 below. The base editor and target correction is shown alongside the relevant guide sequence. Associated amino acid changes in the Niemann-Pick C1 (NPC1) protein are also shown. The target nucleotide (C or A) in the guide sequence is capitalized.
To minimize variability, tissue from all conditions was harvested and processed at the same time. A single set of microscope settings was used to collect all images in
For the determination of GFP nuclei (
In the claims articles such as “a,” “an,” and “the” may mean one or more than one unless indicated to the contrary or otherwise evident from the context. Claims or descriptions that include “or” between one or more members of a group are considered satisfied if one, more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process unless indicated to the contrary or otherwise evident from the context. The invention includes embodiments in which exactly one member of the group is present in, employed in, or otherwise relevant to a given product or process. The invention includes embodiments in which more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process.
Furthermore, the invention encompasses all variations, combinations, and permutations in which one or more limitations, elements, clauses, and descriptive terms from one or more of the listed claims is introduced into another claim. For example, any claim that is dependent on another claim can be modified to include one or more limitations found in any other claim that is dependent on the same base claim. Where elements are presented as lists, e.g., in Markush group format, each subgroup of the elements is also disclosed, and any element(s) can be removed from the group. It should it be understood that, in general, where the invention, or aspects of the invention, is/are referred to as comprising particular elements and/or features, certain embodiments of the invention or aspects of the invention consist, or consist essentially of, such elements and/or features. For purposes of simplicity, those embodiments have not been specifically set forth in haec verba herein.
It is also noted that the terms “comprising” and “containing” are intended to be open and permits the inclusion of additional elements or steps. Where ranges are given, endpoints are included. Furthermore, unless otherwise indicated or otherwise evident from the context and understanding of one of ordinary skill in the art, values that are expressed as ranges can assume any specific value or sub-range within the stated ranges in different embodiments of the invention, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise.
This application refers to various issued patents, published patent applications, journal articles, and other publications, all of which are incorporated herein by reference. If there is a conflict between any of the incorporated references and the instant specification, the specification shall control. In addition, any particular embodiment of the present invention that falls within the prior art may be explicitly excluded from any one or more of the claims. Because such embodiments are deemed to be known to one of ordinary skill in the art, they may be excluded even if the exclusion is not set forth explicitly herein. Any particular embodiment of the invention can be excluded from any claim, for any reason, whether or not related to the existence of prior art.
Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments described herein. The scope of the present embodiments described herein is not intended to be limited to the above Description, but rather is as set forth in the appended claims. Those of ordinary skill in the art will appreciate that various changes and modifications to this description may be made without departing from the spirit or scope of the present invention, as defined in the following claims.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Applications, U.S. Ser. No. 62/850,523, filed May 20, 2019, and U.S. Ser. No. 62/949,275, filed Dec. 17, 2019, each of which is incorporated herein by reference.
This invention was made with government support under grant numbers UG3 TR002636, U01 AI142756, RM1 HG009490, R35 GM118062, and R01 EB022376 awarded by the National Institutes of Health. The government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/033873 | 5/20/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62949275 | Dec 2019 | US | |
| 62850523 | May 2019 | US |
