Patent Application
20150261913
The present invention generally relates to the genetic analysis. More particularly, the present invention relates to computerized and pipelined methods for analyzing genomic data.
Since the completion of the human genome project, technological advances have dramatically increased throughput and decreased the cost of human DNA sequencing, facilitating comprehensive interrogation of coding regions of the genome, transcripts, and whole genome sequences. Studies utilizing this technology have illuminated the underlying genetic basis for rare inherited disease syndromes, refined the molecular understanding of cancer pathogenesis, provided a fine map of rare genetic variation connecting rare variants to common disease risk, and in select cases refined clinical diagnosis and medical therapy.
These initial strides and the continued drop in the cost of high-throughput sequencing have prompted predictions of a new era of medicine personalized to individual genetics. However, downstream interpretation of sequence data remains a formidable barrier to full realization of the promise of genomic medicine. Several applications and data resources exist for predicting the effects of genetic variation on human phenotypes, but there does not yet exist a comprehensive, widely accessible application for clinical interpretation of whole genome sequence data.
A methodology is described in embodiment of the present invention for interpretation of genetic and environmental risk in a single participant using a combination of traditional clinical assessment, whole genome sequencing, and integration of genetic and environmental risk factors. An embodiment of the present invention includes an integrated pipeline sequence-to-medical-phenotypes algorithm for interpreting high-throughput human DNA sequencing data. Embodiments of the present invention perform targeted genotyping of clinically relevant variants, rich functional annotation of discovered variants, and prioritize genetic variants according to potential clinical impact, mode of inheritance, and phenotypic presentation. For individual genome sequences, an embodiment of the present invention provides predictive genetic information from personal genomes regarding risk for inherited disease traits and response to pharmacological therapy. For father-mother-child trios, an embodiment of the present invention produces parsimonious fully annotated candidate genetic variants for disease gene discovery and disease diagnosis.
These and other embodiments and advantages can be more fully appreciated upon an understanding of the detailed description of the invention as disclosed below in conjunction with the attached figures.
The following drawings will be used to more fully describe embodiments of the present invention.
Among other things, the present invention relates to methods, techniques, and algorithms that are intended to be implemented in a digital computer system 100 such as generally shown in
Computer system 100 may include at least one central processing unit 102 but may include many processors or processing cores. Computer system 100 may further include memory 104 in different forms such as RAM, ROM, hard disk, optical drives, and removable drives that may further include drive controllers and other hardware. Auxiliary storage 112 may also be include that can be similar to memory 104 but may be more remotely incorporated such as in a distributed computer system with distributed memory capabilities.
Computer system 100 may further include at least one output device 108 such as a display unit, video hardware, or other peripherals (e.g., printer). At least one input device 106 may also be included in computer system 100 that may include a pointing device (e.g., mouse), a text input device (e.g., keyboard), or touch screen.
Communications interfaces 114 also form an important aspect of computer system 100 especially where computer system 100 is deployed as a distributed computer system. Computer interfaces 114 may include LAN network adapters, WAN network adapters, wireless interfaces, Bluetooth interfaces, modems and other networking interfaces as currently available and as may be developed in the future.
Computer system 100 may further include other components 116 that may be generally available components as well as specially developed components for implementation of the present invention. Importantly, computer system 100 incorporates various data buses 116 that are intended to allow for communication of the various components of computer system 100. Data buses 116 include, for example, input/output buses and bus controllers.
Indeed, the present invention is not limited to computer system 100 as known at the time of the invention. Instead, the present invention is intended to be deployed in future computer systems with more advanced technology that can make use of all aspects of the present invention. It is expected that computer technology will continue to advance but one of ordinary skill in the art will be able to take the present disclosure and implement the described teachings on the more advanced computers or other digital devices such as mobile telephones or “smart” televisions as they become available. Moreover, the present invention may be implemented on one or more distributed computers. Still further, the present invention may be implemented in various types of software languages including C, C++, and others. Also, one of ordinary skill in the art is familiar with compiling software source code into executable software that may be stored in various forms and in various media (e.g., magnetic, optical, solid state, etc.). One of ordinary skill in the art is familiar with the use of computers and software languages and, with an understanding of the present disclosure, will be able to implement the present teachings for use on a wide variety of computers.
The present disclosure provides a detailed explanation of the present invention with detailed explanations that allow one of ordinary skill in the art to implement the present invention into a computerized method. Certain of these and other details are not included in the present disclosure so as not to detract from the teachings presented herein but it is understood that one of ordinary skill in the art would be familiar with such details.
Several applications and data resources exist for predicting the effects of individual nucleotide substitutions. These can be broadly classified into one of two categories: 1) resources that provide predictions about pathogenicity of genetic variants in absence of human genotype-phenotype association data, and 2) resources that seek to apply previous human genotype-phenotype association data to re-sequencing (or other genotype) data. The first group of resources utilizes characteristics of amino acid substitutions, putative change in protein secondary structure, disruption of known structural motifs, and several derivative metrics of evolutionary conservation and constraint to provide predictions about pathogenicity of single nucleotide substitutions. The second group of resources links data from previous linkage studies, family co-segregation data, genome wide association scans, and other sources into searchable databases of genotype-phenotype associations.
The first set of resources, while suited to annotation of individual variants with no human genotype-phenotype association data, ignores the large repository of data connecting genetic variation with human disease phenotypes, and provides no clinical context for interpretation of variant annotations. The second set of resources is not well suited to annotation of comprehensive re-sequencing data, contains annotation errors and common polymorphisms, by some estimates comprising approximately >25% of the entries, and is contaminated by descriptions of trait susceptibility loci of questionable clinical relevance.
There does not yet exist, to date, a readily available pipeline for comprehensive clinical interpretation of sequence variants that integrates predicted methods and the bulk of published disease-genotype associations for genetic assessment of inherited disease risk and predicted drug response. Embodiments of the present invention address certain of these shortcomings of the prior art.
Sequence to Medical Phenotypes
Shown in
It should be noted that embodiments of the present invention are shown and described in a pipeline fashion that is amenable to efficient pipeline computerized processing. For example, certain of the steps to be described may be independent of other steps such that they can be performed independently on different processors or processing cores. Moreover, embodiments of the present invention balance the overall methods among various coprocessors. In this way, as additional computational needs are required for certain steps, more processors or processing cores can be dedicated to such steps. Those of ordinary skill in the art will understand that there are many ways of balancing computational resources in a pipeline architecture such as described in embodiment of the present invention.
At step 205, targeted genotype calling is performed. In an embodiment of the present invention, targeted genotype calling is performed with reference to rare disease risk genotypes 208 and drug response phenotypes 210. In another embodiment of the present invention, the computerized task for targeted genotype calling is mapped to a plurality of processors among available processors. The assignment of the number of processors can, for example, be specified through a command line interface, a graphical interface, or through an input file.
In an embodiment of the present invention, a GATK haplotype caller is used for indels and a unified genotype caller for SNVs. In an embodiment, call genotypes are made from the BAM file (if specified) for known rare disease risk variants and drug response variants using, for example, the Human Gene Mutation Database variants in Clinvar and pharmGKB, respectively.
In an embodiment of the present invention, calls are filtered using hard filtering based on, for example, quality, depth, mapping quality, and allele balance. In yet another embodiment, calls are re-annotated to add dbsnp identifiers.
Primary genotype annotation is then performed at step 211 using the results from the queries of rare SNvs, SVs, and indels 206 and rare disease risk genotypes 208. For example, in an embodiment of the present invention, genotype annotation is performed for all variants from the received reference at step 202. In such an embodiment, a .vcf file is used along with an optional .gff input file.
In an embodiment of the present invention, as part of primary genotype annotation 211, a conversion is made to annovar file input format. Conversion to such format facilitates the use of certain computerized methods for functionally annotating genetic variants detected from diverse genomes. For example, with a list of variants with chromosome, start position, end position and observed nucleotides, computerized methods using annovar can identify whether SNPs or indels cause protein coding changes among other things. As noted previously, embodiments of the present invention lend themselves to pipelined processing and processing among various processors or cores. For example, here, individual annovar annotation processes are mapped to a pool of n processes.
In an embodiment of the present invention, intermediate annotation files are created for each of the received datasets (e.g., SNVs, SVs, and indels). Also, the plurality of individual annotations files is collected and reduced to two files (e.g., *.allvars.genome_summary.tsv, and .clinvar.genome_summary.tsv, representing annotated variants from reference and annotated known rare disease risk genotypes) for SNVs/indes1 and one file for SVs (e.g., *.sys.genome_summary.tsv). Such files can be, for example, text files in a tab separated format.
Rare variants in inherited disease genes are then identified at step 212. For example, in an embodiment of the invention, rare variants in inherited disease genes are categorized into a plurality of tiers. For example, as shown in
As a final filter for both previously reported variants in monogenic disease genes and previously unreported, rare variants in monogenic disease genes, an embodiment of the present invention uses catalogs of local allele frequency and genotype information to exclude variants that are observed more frequently than would be expected in the local sequencing environment (according to user defined criteria). This filter serves to identify and exclude variants whose previously unappreciated high allele frequency is a result of false negatives in population genetic surveys or systematic false positives specific to the sequence assessment pipeline. Similar filters have proven effective in excluding such systematic artifacts in other contexts.
As would be known to those of ordinary skill in the art upon an understanding of the present invention, the criteria for the various tiers can be modified to meet particular needs that may arise in different situations.
Known variants in inherited disease genes are identified at step 214. For example, in an embodiment of the present invention, known variants in inherited disease genes are categorized into a plurality of tiers. For example as shown in
As would be known to those of ordinary skill in the art upon an understanding of the present invention, the criteria for the various tiers can be modified to meet particular needs that may arise in different situations.
In an embodiment of the present invention, rare SVs in inherited disease genese (e.g., genes specified by a user or in an clinvar default) are filtered by a predetermined allele frequency in allele frequency databases using a rarity criteria as discussed above. In an embodiment, these criteria are user specified. Information is retained if it is predicted to cause exonic disruption (e.g., annotated as exonic) of inherited disease genes. In an embodiment, user input information (e.g., user input or input files) identifies inherited disease genes for individuals.
Haplotype assignment is then performed at step 213 as shown in
As shown in
Embodiments of the present invention find wide application in genomics. For example, applications for embodiments of the present invention include: 1) Identification of medically actionable genetic variants with disease risk implications in pre-symptomatic individuals in WGS data; 2) Identification of genetic variants in WGS associated with drug response; and 3) Identification of genetic variants in WGS associated with disease in families and individuals.
Embodiments of the present invention present advantages over the prior ar. For example, embodiments of the present invention include fully integrated sets of methods for clinical interpretation of whole genome sequence data. Also, the present invention provides methods for automated haplotype identification and comprehensive annotation of drug response predictions from whole genome sequence data. Embodiments of the present invention provide methods for identifying apparent de novo mutations in father-mother-child trios while excluding systematic artifacts. Also, embodiments seamlessly integrate with a variety of variant call outputs and sequence maps. Embodiments also provide reference-agnostic disease risk prediction and provide comprehensive disease risk prediction and drug response prediction using efficient and fast methods and data sources for haplotype determination and annotation.
Alternative embodiments of the present invention are shown in
Methods for clinical interpretation in the context of disease gene finding in inherited disease syndromes and predictive genetic variant annotation are shown in
It should be noted that embodiments of the present invention are shown and described in a pipeline fashion that is amenable to efficient pipeline computerized processing. For example, certain of the steps to be described may be independent of other steps such that they can be performed independently on different processors or processing cores. Moreover, embodiments of the present invention balance the overall methods among various coprocessors. In this way, as additional computational needs are required for certain steps, more processors or processing cores can be dedicated to such steps. Those of ordinary skill in the art will understand that there are many ways of balancing computational resources in a pipeline architecture such as described in embodiment of the present invention.
Discovery of Variants from an Ethnically-Matched Reference Sequence and Genotyping of Clinically Relevant Variants
High-throughput re-sequencing with current sequencing platforms requires a reference genome for sequence assembly and variant identification. The reference genome that is currently used for alignment of human re-sequencing data and variant identification (the NCBI reference genome) is derived from a collection of DNA samples from a small number of anonymous volunteers. It is currently the only “finished-grade” human genome in that it was assembled de-novo from long sequence reads and covers approximately 99% of the euchromatic human genome. However, it represents a small sampling of human genetic variation. As such, at approximately 1.6 million genomic positions, the NCBI reference sequence differs from the major allele in each of the three Haplotype Map (HapMap) populations, and at approximately 800,000 positions, the minor allele for all three population groups is represented on the NCBI reference sequence. These minor alleles span approximately 4,500 variant positions associated with common complex disease traits.
To address these issues, a major allele reference sequence for each of the three major HapMap populations was developed. This is utilized it in mapping short read data and variant identification using high-throughput sequencing. Application of this approach to variant identification in whole genome sequence data from a nuclear family of four reduced genotype error by approximately 40% at disease-associated variant loci and resulted in greater concordance with genotype calls from orthogonal genotyping technologies.
In an embodiment of the present invention, the methods of the present invention can use major allele reference genomes if the ethnicity of study participants is known. In an alternative embodiment, it may be preferable to use standard (or SNP-masked) standard reference sequences if ethnicity is not known or if performing joint genotype calling of a multi-ethnic study cohort. In the latter case, alignment can be performed using an ethnicity-specific major allele reference to maximize sensitivity of short read alignment, and a standard or SNP-masked standard reference sequence may be used for variant and genotype identification, thereby standardizing the reference allele in the variant call file.
There are well-document disease risk and drug response alleles in the reference sequence, most notably Factor V Leiden allele associated with hereditary thrombophilia. Comparison of genome sequence data that is homozygous for these alleles to this reference sequence will naturally not produce a variant call. This issue is partially addressed by the use of major allele reference sequences. A more comprehensive approach is to perform targeted genotype calling of all loci considered to be of phenotypic importance. This approach is reference agnostic up to reference bias associated with short read alignment and mapping. Embodiments of the present invention use input interval call files representing previously reported Mendelian disease associated loci and loci associated with drug response to provide targeted genotype calls, irrespective of reference base, using the GATK Unified Genotyper (for SNVs) and Haplotype Caller (for indels). Embodiments of the present invention also provide metrics for coverage of loci with known importance to human health and disease, thereby providing confidence that a disease-associated allele is indeed not present, rather than just under-sequenced or otherwise not confidently ascertained. As compared with methods that store diploid calls for all reference genomic positions, the approach to genotype interrogation facilitates downstream variant annotation while minimizing storage requirements for variant data. To facilitate updated genotype identification as new loci of relevance to human health and disease are discovered, binary alignment (BAM) files from the secondary sequence analysis are retained for future analysis.
Annotation of Genetic Variants with Respect to Functional Genetic and Clinical Phenotypes
Rich functional genomic annotation is a prerequisite to sequence interpretation pipelines that aim to provide testable biological hypotheses about the basis for described disease syndromes and for disease risk and drug response prognostication. The annovar framework was extended to provide rich gene-based, functional genomic, regulatory, allele frequency, and phenotypic annotation. This basic annotation pipeline, stanovar, provides 94 annotations for SNVs and indels in .vcf format (Table 1 attached as Appendix A) and 39 annotations for SVs in .gff format (Table 2 attached as Appendix B).
An embodiment of the present invention can also leverage gene coexpression network topology information to provide quantitative prior expectations about gene-level pathogenicity for contextualizing individual variation data. For example, output of an embodiment of the present invention can be used to identify genetic variation occurring in genes that are coexpressed with known disease genes, thereby implicating by association variants perturbing certain network topologies. In an embodiment, the default module comes pre-loaded with gene coexpression network topology representing gene expression microarray data from 75 normal, unused human donor hearts, tissue from 49 human hearts with right- or left-ventricular hypertrophy, and 436 explanted human hearts with dilated cardiomyopathy. Disease-specific topologies can be used to assess dynamic gene-gene interactions that are context specific.
Bioinformatic Prioritization of Candidate Mendelian Disease Risk Variants
While rich annotation of genetic variants and genotypes with potential clinical significance is a pre-requisite for downstream analysis, prioritization of variants for manual review, in the case of individual genome interpretation, or intersection with inheritance state information, in the case of disease gene identification projects, is arguably the most crucial part of the analytical pipeline. An embodiment of the present invention uses a prioritization heuristic that at once provides a parsimonious set of candidates for manual review and a comprehensive assessment of previously reported genetic variation.
The overall heuristic for prioritization of previously reported variants in monogenic disease genes, as well as rare and novel variants in monogenic disease genes with no previously reported phenotypic association, is described in
The information from step 408 (as well as 406 and 404) is also referenced against rare variants in ClinVar genes 412 to generate candidates for rare non-HGMD variants in high impact genes at step 416. In an embodiments, the rare non-HGMD variants in high impact genes are categorized into tiers (e.g., Tiers 1-3) in a similar manner as discussed above. For example, in an embodiment, Tier 1 represents loss of function candidates; Tier 2 represents missense/nonframeshit conserved variants, and Tier 3 represents missense/nonframeshift predicted pathogenic variants. In an embodiment, Tier 4 (not shown) represents all variants not meeting criteria for Tiers 1-3.
The results form steps 414 and 416 are then collected at step 418 as high impact disease risk candidates. A sequence validation is performed at step 420 in an embodiment of the present invention. The resulting candidates are then used in conjunction with the results of a manual literature review at step 422 to generate high impact disease risk and carrier status information at step 424.
It should be noted that embodiments of the present invention are shown and described in a pipeline fashion that is amenable to efficient pipeline computerized processing. For example, certain of the steps to be described may be independent of other steps such that they can be performed independently on different processors or processing cores. Moreover, embodiments of the present invention balance the overall methods among various coprocessors. In this way, as additional computational needs are required for certain steps, more processors or processing cores can be dedicated to such steps. Those of ordinary skill in the art will understand that there are many ways of balancing computational resources in a pipeline architecture such as described in embodiment of the present invention.
In an embodiment, a default mode first reduces all variants to a set that occurs within 2,725 genes cataloged in ClinVar (2,716 in females due to cataloged disease associations within nine genes on the Y chromosome), manually curated to exclude drug response associations and common disease susceptibility loci. Alternatively, gene sets can be provided by the user and utilized for genetic variant filtering based on the phenotypic features of the disease queried.
Previously reported variants in disease mutation catalogs include a significant number of common polymorphisms, mapping errors, legacy coordinates, and common disease susceptibility loci that are unlikely to be relevant to monogenic disease risk. Thus, an embodiment of the present invention prioritizes variants previously reported in the Human Gene Mutation Database (HGMD) first by expected pathogenicity and next by allele frequency. Previously reported variants cataloged in HGMD are separated into four tiers of potential pathogenicity:
Tier 1: Loss of function variants (splice dinucleotide disrupting, nonsense, nonstop, and frameshift indels).
Tier 2: All rare variants cataloged in HGMD, regardless of functional annotation. Rarity is defined as MAF no greater than 1% (default, can use alternative cut-offs using optional flags in command line) in any of the following population genetic surveys: ethnically-matched population in HapMap 2 and 3, the 1000 genomes phase 1 data27 from an ethnically-matched super population, and global allele frequency, the 1000 genomes pilot 1 project global allele frequency, 69 publicly available genomes released by Complete Genomics, and the NHLBI Grand Opportunity exome sequencing project global allele frequency.
Tier 3: All non-rare missense and non-frameshift indels.
Tier 4: All variants not meeting criteria for tiers 1-3.
Variants meeting criteria for tiers 1-3 are retained for downstream manual review in the case of individual genome interpretation, and for intersection with inheritance state information in the case of disease-targeted analyses. As the expected allele frequency of potentially pathogenic variants is likely to vary greatly with disease prevalence, penetrance, and mode of inheritance, allele frequency filters are not used for tiers one and three, thereby allowing for prioritization of functional alleles with previously described disease associations that would not otherwise pass strict allele frequency filters, for instance the deltaF508 allele in CFTR or the Factor V Leiden allele.
Rare and private variation, as a result of recent population expansion and purifying selection, continues to constitute a significant proportion of human genetic variation, even in large surveys of individual variation. Some of these rare and private alleles will have monogenic disease risk and carrier status relevance, and therefore an embodiment of the present invention also prioritizes select previously unreported, but potentially pathogenic, rare and novel variants in monogenic disease genes, incorporating consensus evidence for evolutionary constraint/conservation and pathogenicity prediction. These computational methods for scoring genetic variants have, in isolation, modest classification accuracy and inter-algorithm concordance. Approaches to rating the potential pathogenicity of variants based on consensus of commonly used prediction algorithms have been shown to have superior calibration and discriminative accuracy when compared with individual predictions. An embodiment of the present invention imposes a prior expectation that such alleles are more likely to occur in genes in which previously reported variants have produced Mendelian disease phenotypes, but also archives and categorizes all other variants for review and potential reclassification as genetic knowledge expands, or for intersection with inheritance state data. Rare (defined as above) and novel variants with no previously described phenotype association in monogenic disease genes are prioritized into four tiers of potential pathogenicity in an embodiment of the present invention:
Tier 1. Rare loss of function variants, defined as above.
Tier 2: Rare missense or non-frameshift indels affecting nucleotides with consensus evidence by both algorithms considered for evolutionary conservation/constraint according to the following values cataloged in the database of nonsynonymous functional predictions: GERP++score>2; PhyloPnew>0.95.
Tier 3: Rare missense or non-frameshift indels with predicted pathogenicity by three or more algorithms according to the following definitions as cataloged in the database of nonsynoymous functional predictions: SIFT, “Damaging”; LRT, “Deleterious”; PolyPhen2, “Probably damaging” or “Possibly damaging”; Mutation taster, “Disease causing automatic” or “disease causing”.
Tier 4: All rare variants not meeting criteria for tiers 1-3.
Annotation of Personal Genetic Variation Associated with Drug Response
Predicting drug response from WGS data requires generation of best-guess haplotypes from short-read sequence data for which haplotype phase is often not determined molecularly. An embodiment of the present invention produces best-guess haplotype pairs from confidently genotyped SNVs and indels identified as above. To do this embodiment first creates skeleton haplotype pairs using all confidently identified homozygous SNVs. The full set of complementary haplotypes is then generated using heterozygous variant calls. A perfect-match search is performed for each haplotype and its complement among described haplotypes defining the known “star” alleles associated with clinical drug response. If a perfect match is not found, the set of possible haplotype pairs is given but no star allele assignment is attempted. If more than one pair of possible star alleles is found matching possible haplotypes generated from WGS data, all possible star allele combinations are reported.
An embodiment of the present invention does not provide haplotype resolution beyond that suggested by the confidently called genotypes. That is, if a variant is not confidently called, haplotypes that are uniquely defined by these “tags” variants are not disambiguated from other possible star allele-defining haplotypes, and a set of possible star alleles corresponding to each reduced haplotype and its conjugate are reported. The haplotype determination is purposefully designed to only give high-confidence predictions, leaving the task of disambiguating star alleles in the setting of uncertain genotype calls or uncommon haplotypes to a human curator.
Another embodiment also annotates and reports single variant drug response associations cataloged in the PharmGKB knowledgebase at a level of evidence (for definitions, see http://www.pharmgkb.org/page/clinAnnLevels) defined by the user as shown in the embodiment of
It should be noted that embodiments of the present invention are shown and described in a pipeline fashion that is amenable to efficient pipeline computerized processing. For example, certain of the steps to be described may be independent of other steps such that they can be performed independently on different processors or processing cores. Moreover, embodiments of the present invention balance the overall methods among various coprocessors. In this way, as additional computational needs are required for certain steps, more processors or processing cores can be dedicated to such steps. Those of ordinary skill in the art will understand that there are many ways of balancing computational resources in a pipeline architecture such as described in embodiment of the present invention.
Disease Associated Variant Discovery in Father-Mother-Child Trios with Simplex Phenotypes
Genome-wide genetic interrogation in father-mother-child trios with apparently simplex phenotypes can be a powerful tool for genetic association discovery. Classically these investigations are performed using discrete filtering to identify apparent de novo, compound heterozygous, and rare homozygous mutations. De novo mutations are typically discovered via searching for Mendelian inheritance abnormalities (MIAs) that are consistent with the segregation of phenotypes within the family. Discrete filtering is encumbered by several challenges, however. First, the true per-generation de novo mutation rate is two to three orders of magnitude lower than the sequence error rate using current high throughput sequencing technology. In addition to stochastic error modes, there are systematic error modes arising from sequences in the human reference genome that are compressed relative to common repetitive sequences, low complexity and GC and homopolymer rich regions, and other regions of the human genome that are problematic to accurately sequence, align, or genotype. Roach, et al, developed an HMM-based classifier to identify these regions in family quartets and also to provide relative inheritance state information for WGS. An embodiment of the present invention utilizes a simplified HMM classifier that bins WGS or WES data into one of three categories (three hidden states): “good data”, “compression”, or “MIA-rich” regions. The latter two categories represent variant data that is highly likely to contain systematic artifact and can be excluded from downstream analysis and-or interpretation. An embodiment writes this information in the “Filter” field of standard vcf output, allowing for soft-filtering or manual inspection of these regions. An embodiment uses chromosomal distance between variant markers as a prior expectation in the HMM, thereby facilitating for the first time the use of this HMM-based approach in WES, which by virtue of sequence capture is sparse outside targeted regions and dense within targeted regions.
Second, apparently simplex disease phenotypes can arise from a variety of possible underlying genetic architectures and modes of inheritance, and pre-specifying one mode can lead to a lack of sensitivity. To address this, once HMM-based regional classification has been performed, an embodiment of the present invention will output 1) apparent de novo events, 2) all instances of compound heterozygosity in a gene in which at least one variant in the pair is rare according to user specific criteria 3) rare homozygous mutations, and 4) instances of apparent hemizygosity which are candidates for loss of function, 5) rare variants in known inherited disease genes fitting an autosomal dominant inheritance model with reduced penetrance. This output can be used for manual inspection in single trio studies or as a prior expectation for gene regions fed forward into collapsing statistics if a cohort of trios is studied. In the latter case an embodiment leverages inheritance information to reduce the number of gene regions queried and thus the number of statistical comparisons performed between case and control cohorts.
Inputs, Implementation and Parallelization
An embodiment of the present invention accepts as required input a vcf file prepared by Illumina Isaac, GATK, the Complete Genomics variant discovery pipeline, or Real Time Genomics. Optional inputs include 1) binary alignment map file, required for targeted genotype calling and annotation of known inherited disease risk alleles and pharmacogenomic annotation, 2) genome feature format file describing structural variant events, 3) local site frequency spectrum for filtering of inherited disease risk candidates. In trio mode, an embodiment requires jointly called genotypes and sample identifiers for father, mother, and child. Initial annotation of genetic variants for gene, functional genomic, and clinical phenotypes (stanovar) is performed using python/perl and parallelized using the “multiprocessing” module in python. Processing time for stanovar scales roughly as 1/n, where n is the number of processors allocated to the task. An embodiment is implemented in cython/python/shell and also parallelized using the “multiprocessing” modules in python.
Other embodiments of the present invention include but are not limited to:
Population wide sequencing is a near-term reality in medicine, and the ability to interpret genome sequences from individuals will determine the commercial viability of this technology for advancing personalized health care. With these genome interpretation methods as disclosed herein, a solution is presented for rich genome annotation, clinical genotype discovery, and identification of clinically important disease risk and drug response predictions in whole genome sequence data.
Further details about embodiments of the present invention are included in Tables 1 and 2 included in the Appendixes A and B, respectively.
It should be appreciated by those skilled in the art that the specific embodiments disclosed herein may be readily utilized as a basis for modifying or designing other algorithms or systems. It should also be appreciated by those skilled in the art that such modifications do not depart from the scope of the invention as set forth in the appended claims. For example, variations to the methods can include changes that may improve the accuracy or flexibility of the disclosed methods.
This application claims priority to U.S. Provisional Application No. 61/950,957 filed Mar. 11, 2014, which is hereby incorporated by reference in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 61950957 | Mar 2014 | US |
