Patent Application
20100021913
The present invention relates to a method for diagnosing Alzheimer's disease using PKC-elicited gene expression profiles.
Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the progressive decline of memory and cognitive functions. Dementia associated with AD is referred to as senile dementia of the Alzheimer's type (SDAT) in usage with Alzheimer's disease. AD is characterized clinically by progressive loss of memory, cognition, reasoning, judgment, and emotional stability that gradually leads to profound mental deterioration and ultimately, death. Although there are many hypotheses for the possible mechanisms of AD, one central theory is that the excessive formation and accumulation of toxic beta-amyloid (Aβ) peptides either directly or indirectly affects a variety of cellular events and leads to neuronal damage and cell death (Selkoe, Neuron. 1991; 6(4):487-98 1991; Selkoe, J Clin Invest. 2002; 110(10):1375-81).
AD is a progressive disorder with a mean duration of around 8-15 years between onset of clinical symptoms and death. AD is believed to represent the seventh most common medical cause of death and affects about 5 million people in the United States. The prevalence is expected to reach 7.7 million by 2030. About 1 in 8 people over the age of 65, 13% of this population, have AD (Alzheimer's Association 2008 Alzheimer's Disease Facts and Figures). AD currently affects about 15 million people world-wide (including all races and ethnic groups) and owing to the relative increase of elderly people in the population its prevalence is likely to increase over the next two to three decades. AD is at present incurable.
To date, there is limited opportunity for prophylactic intervention for AD because of insufficient diagnostic methods. At present, a definitive diagnosis of AD requires observing lesions in the brain tissue of patients post-mortem or, rarely, in small biopsied samples of brain tissue taken during an invasive neurosurgical procedure. Nevertheless, physicians routinely attempt to distinguish AD from other forms of dementia based on a battery of symptoms, relying on the known correlation between such symptoms and the lesions observed in biopsies. Tests currently used to diagnose AD include combinations of qualitative questionnaires such as the Mini-Mental State Examination (MMSE), the Mini-Cognitive Examination, and the AD Cooperative Study-Activities of Daily Living Scale (ADCS-ADL); physical and neurological evaluation; and structural (MRI, CT) and functional brain imaging (PET; FDG-PET). These tests are typically conducted to rule out other disease or conditions rather than to provide a definitive diagnosis of AD.
Some methods exist for detecting pathogenic biomarkers for AD, such as Aβ, Tau, and Neural thread protein/AD7C in living subjects. For example, detection of Aβ in a living subject include direct (imaging) or indirect (biochemical) detection. In vivo imaging of Aβ can be achieved using radioiodinated flavone derivatives as imaging agents (Ono et al., J Med Chem. 2005; 48(23):7253-60) and with amyloid binding dyes such as putrescein conjugated to a 40-residue radioiodinated A peptide (yielding 125I-PUT-A 1-40). This agent was shown to cross the blood-brain barrier and bind to Aβ plaques (Wengenack et al., Nature Biotechnology. 2000; 18(8): 868-72). Imaging of Aβ also was shown using stilbene [11C]SB-13 and the benzothiazole [11C]6-OH-BTA-1 (also known as [11C]PIB) (Nicholaas et al., Am J Geriatr Psychiatry. 2004; 12:584-595).
Quantitation of Aβ (1-40) in the peripheral blood also has been demonstrated using high-performance liquid chromatography coupled with tandem mass spectrometry in a linear ion trap (Du et al., J Biomol Tech. 2005; 16(4):356-63). Detection of single Aβ protein aggregates in the cerebrospinal fluid of Alzheimer's patients by fluorescence correlation spectroscopy also has been described (Pitschke et al., Nature Medicine. 1998; 4: 832-834). U.S. Pat. No. 5,593,846 describes a method for detecting soluble Aβ. Indirect detection of Aβ peptide and receptor for advanced glycation end products (RAGE) using antibodies also has been described. Lastly, biochemical detection of increased BACE-1 activity in cerebrospinal fluid using chromogenic substrates also has been postulated as diagnostic or prognostic indicator of AD (Verheijen et al., Clin Chem. 2006; 52:1168-1174). Other methods include detection of Tau, and Neural thread protein/AD7C in the cerebrospinal fluid.
In an attempt to improve treatment and diagnosis of AD, numerous gene-expression profiles have been generated to compare genes expressed in post-mortem brain tissue with those expressed normal brain tissue using various techniques including microarray laser capture microdissection (Loring et al., DNA and Cell Biology. 2001; 20(11): 683-95; Mufson et al., Neurochem. Res. 2003; 27(10): 1035-48; Dunckley et al., Neurobiol Aging. Oct. 1, 2005; Brooks et al., Brain Res. 2007; 1127(1):127-35; Liang et al., Physiological Genomics. 2008; 33:240-256; Liang et al., Proc Natl Acad Sci USA. Mar. 10, 2008); Some gene-expression profiles using peripheral tissues, such as lymphocytes or fibroblasts, also have been generated in an attempt to identify gene expression profiles associated with familial (inherited) AD or evaluate the effect of a potential treatment on differentially expressed genes (Nagasaka et al., Proc. Natl. Acad. Sci. USA . 2005; 102(41): 14854-14859).
Current diagnostic measures for AD include identification of a clinical core of early, progressive and significant episodic memory loss plus one or more abnormal biomarkers (biological indicators) characteristic of AD, including atrophy (wasting) of the temporal lobe as shown on MRI; abnormal Aβ protein concentrations in the cerebrospinal fluid; a specific pattern showing reduced glucose metabolism on PET scans of the brain; and a genetic mutation associated with within the immediate family.
Like the physical and mental examinations, the foregoing methods are not yet totally reliable or accurate for a diagnosis of Alzheimer's because the same gene patterns are found in other diseases or conditions. As a result, the costs of diagnosing AD are enormous because of the numerous tests and specialists involved and because the inability to diagnose Alzheimer's in early stages precludes patients and their families from adequately planning for the future, increasing costs for long-term care. In addition, estimates rates of misdiagnoses or no definitive diagnosis are in the range of 50-75%.
There remains a need for a simpler way to achieve more definitive diagnoses of AD that are less expensive and invasive, more accurate, and which can be used at an earlier stage for quicker intervention. Importantly, because the neurodegenerative process and substantial cell loss likely begins well before manifestation of the cognitive symptoms of AD, an effective diagnostic test that could more accurately diagnose AD, including early AD and even a pre-disposition to AD, would be invaluable.
The invention provides methods for diagnosing Alzheimer's disease (AD). These methods are based upon detecting changes in gene expression following activation of protein kinase C (PKC). Protein kinase C (PKC) is one of the largest gene families of protein kinase (Liu and Heckman, Cell Signal. 1998; 10:529-542). Several PKC isozymes are expressed in the brain, including PKC, PKCβ1, PKCβ2, PKCδ, PKCε, and PKCγ. PKC is primarily a cytosolic protein, but with stimulation it translocates to the membrane. PKC has been shown to be involved in numerous biochemical processes relevant to Alzheimer's disease. Deficits of PKC isoforms have been found in AD brain tissue and in fibroblasts from AD patients. PKC also activates TNF-alpha converting enzyme (TACE), which is an enzyme that is involved in the proteolytic conversion of membrane-bound amyloid precursor protein (APP) to its non-pathogenic soluble form, known as soluble APP-alpha or sAPPalpha (Alkon et al., Trends in Pharmacological Sciences. 2007; 28(2): 51-60; Hurtado et al., Neuropharmacology. 2001; 40(8): 1094-1102). These sAPPα-producing enzymes are referred to generically as alpha-secretases. Activation of TACE by PKC also reduces cellular levels of pathogenic Aβ, which is produced by cleavage of APP by the beta-secretase enzyme (BACE). This is likely due to the fact that the TACE cleavage site is within the Aβ domain of APP. Overexpression of PKCε has been shown to selectively increased the activity of endothelin-converting enzyme, which degrades Aβ (Choi et al., Proc. Natl. Acad. Sci. USA. 2006; 103(21): 8215-8220). Moreover, studies have demonstrated that one PKC activator, bryostatin-1, reduces the levels of soluble Aβ and enhances recent memory (Etcheberrigaray et al., Proc Natl Acad Sci USA. 2004; 101(30):11141-6; U.S. Pat. No. 6,825,229).
In addition, other studies have demonstrated that the translocated PKC can phosphorylate glutamate receptors, including NMDA receptors, as well as other proteins that are located in the postsynaptic density (Suzuki et al., Brain Res. 1993; 619:69-75). PKC has several impacts on NMDA receptors (MacDonald et al., Curr Drug Targets. 2001; 2:299-312). Specifically, PKC enhances the surface expression of NMDA receptors (Xiong et al., Mol Pharmacol. 1998; 54:1055-1063; Lan et al., Nat Neurosci. 2001; 4:382-390). Calcium flux through NMDA receptors is thought to play a critical role in synaptic plasticity, a cellular mechanism for learning and memory. One of the drugs approved to treat AD, memantine, binds to the NMDA receptor and inhibit the prolonged influx of calcium ions which forms the basis of neuronal excitotoxicity in AD.
Because the various PKC isozymes are involved in AD, the detection of Alzheimer's disease-specific differences in PKC-elicited gene expression and function in peripheral tissues provides the basis for highly practical and efficient tests for the early diagnosis of Alzheimer's disease, and provide a basis for identifying targets for therapeutic drug development.
Protein Kinase C refers to any isoforms of PKC encoded by a PKC gene. The PKC gene family consists presently of 11 genes which are divided into four subgrounds: 1) classical PKCα (alpha), β1, β2 (beta) (β1 and β2 are alternatively spliced forms of the same gene) and γ (gamma), 2) novel PKCδ (delta), ε (epsilon), η (eta) and 0 (theta), 3) atypical PKCξ (zeta), λ (lambda), η (eta) and ι (iota) and 4) PKCμ (mu). The α, β1, β2, and γ isoforms are calcium ion dependent, phospholipid and diacylglycerol-dependent and represent the classical isoforms of PKC, whereas the other isoforms are activated by phospholipid and diacylglycerol but are not dependent on calcium. All isoforms encompass 5 variable (V1-V5) regions, and the α, β1, β2, and γ isoforms contain four (C1-C4) structural domains which are highly conserved. All isoforms except PKC α, β1, β2, and γ lack the C2 domain, and the λ, η isoforms also lack nine of two cysteine-rich zinc finger domains in C1 to which diacylglycerol binds. The C1 domain also contains the pseudosubstrate sequence which is highly conserved among all isoforms, and which serves an autoregulatory function by blocking the substrate-binding site to produce an inactive conformation of the enzyme (House et al., Science. 1997; 238:1726-1728).
The term “Alzheimer's Disease” or “AD” refers to any condition where Aβ and/or neurofibrillary tangles eventually accumulates in the cells of the central nervous system, which accumulation that cannot be attributed to other disease or conditions such as CAA. AD may be heritable in a Familial manifestation, or may be sporadic. As used herein, AD includes Familial, Sporadic, as well as intermediates and subgroups thereof based on phenotypic manifestations. In addition, this term includes the development of Aβ in subjects having Down's Syndrome.
The term “Sporadic AD” refers to AD that develops later in life, usually after the age of about 65, and is not associated with a family history of AD or a mutation in a gene identified as being a risk factor for AD.
The term young-onset refers to AD that occurs in a person under age about 65. Young-onset includes but is not limited to Familial AD.
Familial AD refers to AD associated with inherited mutations in the presenilin-1 gene (PSEN-1), presenilin-2 gene (PSEN-2); the gene encoding Amyloid beta precursor protein (APP), and/or the gene encoding apolipoprotein E (APOE).
Early-stage AD refers to the stage of AD associated with moderate symptoms of cognitive decline such as memory loss or confusion. Memory loss or other cognitive deficits are noticeable, yet the person can compensate for them and continue to function independently. This stage correlates with Stage 4 of the Functional Assessment Staging (FAST) scale or mild AD according to the criteria defined in the Diagnostic and Statistical Manual of Mental disorders, 4th Edition (DSM-IV-TR) (published by the American Psychiatric Association), NINCDS-ADRDA, or MMSE.
Mild Cognitive Impairment (MCI) refers to a transition stage between the cognitive changes of normal aging and AD. A subject with MCI has cognitive impairments beyond that expected for their age and education, but that do not interfere significantly with their daily activities. A person with MCI may have impairments with memory, language, or another mental function. Not all subjects with MCI develop AD. As used herein, a subject with MCI is considered at risk for developing AD.
Other risk factors for AD are advancing age, mutations in PSEN-1, PSEN-2, APP and APOE, and
As used herein, the term “subject” means a mammal. In one embodiment, the subject is a human.
The term “normal subject,” as used herein, is relative to AD. That is, the subject does not exhibit AD, is not diagnosed with the specified disease, and is not at risk for developing the disease.
“Peripheral tissue” refers to a tissue that is not derived from neuroectoderm, and specifically includes olfactory epithelium, tongue, skin (including dermis and/or epidermis), and mucosal layers of the body.
The term “differentially expressed” or “differential expression” as used herein refers to a measurement of a cellular constituent varies in two samples, a control sample and a test sample. The cellular constituent can be either upregulated in the experiment relative to the control or downregulated in the experiment relative to the control sample.
As used herein, the phrase “detecting the level of expression” includes methods that quantitate expression levels as well as methods that determine whether a gene of interest is expressed at all. The detection can be qualitative or quantitative. In one specific embodiment, the differential expression is statistically significant
As used herein, “upregulating” or “upregulation” means detecting an increased the amount or activity of a gene or gene product relative to a baseline or control state, through any mechanism including, but not limited to increased transcription, translation and/or increased stability of the transcript or protein product. Increased expression in a test cell includes a situation where the corresponding gene in a control cell is either unchanged by PKC activation or is downregulated in response to PKC activation.
As used herein, “down regulating” or “downregulation” refers to detecting a decrease in the amount or activity of a gene or gene product relative to a baseline or control state, through any mechanism including, but not limited to decreased transcription, translation and/or decreased stability of the transcript or protein product. Decreased expression in a test cell includes a situation where the corresponding gene in a control cell is either unchanged by PKC activation or is upregulated in response to PKC activation.
A “change in gene expression” refers to detection of upregulation or downregulation.
The term “microarray” or “nucleic acid microarray” refers to a substrate-bound collection of plural nucleic acids, hybridization to each of the plurality of bound nucleic acids being separately detectable. The substrate can be solid or porous, planar or non-planar, unitary or distributed. Microarrays or nucleic acid microarrays include all the devices so called in Schena (ed.), DNA Microarrays: A Practical Approach (Practical Approach Series), Oxford University Press (1999); Nature Genet. 21(1)(suppl.)1-60 (1999); Schena (ed.), Microarray Biochip: Tools and Technology, Eaton Publishing Company/BioTechniques Books Division (2000). These microarrays include substrate-bound collections of plural nucleic acids in which the plurality of nucleic acids are disposed on a plurality of beads, rather than on a unitary planar substrate, as is described, inter alia, in Brenner et al., Proc. Natl. Acad. Sci. USA 2000; 97(4):1665-1670.
The terms “about” and “approximately” shall generally mean an acceptable degree of error for the quantity measured given the nature or precision of the measurements. Typical, exemplary degrees of error are within 20 percent (%), preferably within 10%, and more preferably within 5% of a given value or range of values. Alternatively, and particularly in biological systems, the terms “about” and “approximately” may mean values that are within an order of magnitude, preferably within 5-fold and more preferably within 2-fold of a given value. Numerical quantities given herein are approximate unless stated otherwise, meaning that the term “about” or “approximately” can be inferred when not expressly stated.
In one embodiment, the invention provides a method of diagnosing AD by detecting differences in the expression levels of genes in cells from a subject suspected of developing or having AD, in response to stimulation with a PKC activator (“test cells”), compared to expression of the same genes in normal control cells (“control cells”) following stimulation with a PKC activator. In a specific embodiment, the control cells are derived age-matched control subjects and are stimulated with the same PKC activator as the test cells.
In another embodiment of the invention, increased gene expression in PKC-stimulated test cells compared to PKC-stimulated control cells (upregulation) indicates the presence of AD. In another aspect, decreased gene expression in stimulated test cells compared to PKC-stimulated control cells (downregulation) indicates the presence of AD. In a third aspect, absence of increased gene expression in stimulated test cells compared to PKC-stimulated control cells indicates the presence of AD. In a fourth aspect, absence of decreased expression in stimulated test cells compared to PKC-stimulated control cells indicates the presence of AD.
In another specific embodiment, the present invention provides a method for diagnosing early-stage AD by detecting the differential changes in gene expression. In specific embodiments, the method of the invention can be used to distinguish Alzheimer's pathology or dementia from that associated with other forms of dementia, such as frontotemporal degenerative dementias (e.g., Pick's disease, corticobasal ganglionic degenerations, and frontotemporal dementia), Huntington's disease, Creutzfeldt Jakob disease, Parkinson's disease, cerebrovascular disease, head trauma, and substance abuse.
In a further embodiment, the invention provides a method of evaluating disease progression by applying the methods to two or more samples from the same patient taken on separate occasions. This embodiment can also be used to evaluate the effect of any AD treatment administered after the first sample is taken but before the send sample is taken. Exemplary AD treatments that can be evaluated include Namenda® (memantine), Aricept® (donapazil) and Razadyne® (galantamine), an Exelon® (rivastigmine).
The present invention further provides a method of screening therapeutic substances for the treatment or prevention of AD by evaluating the effects of a test agent on the differential expression of genes according to the methods described herein.
In another embodiment, the present invention provides kits to carry out the diagnostic method of the present invention.
Table 1 provides the GenBank accession number for the genes identified to be down-regulated in the AD cells compared with the control cells. Table 2 provides the GenBank accession number for the genes identified to be upregulated in the AD cells compared with the control cells. Table 3 provides the specific genes and their relationship(s), and molecular biological and cellular functions.
In specific embodiments, the diagnostic method of the present invention comprises detecting differential expression in the control sample and the test sample of at least two genes listed in Table 1 or Table 2 in Example 1, below. In another specific embodiment, the diagnostic method of the present invention comprises detecting differential expression in the control sample and the test sample of at least five genes listed in Table 1 or Table 2. In a further specific embodiment, the diagnostic method of the present invention comprises detecting differential expression in the control sample and the test sample of at least ten genes listed in Table 1 or Table 2. In yet a further specific embodiment, the diagnostic method of the present invention comprises detecting differential expression in the control sample and the test sample of at least fifteen genes listed in Table 1 or Table 2. The specific genes and their relationship(s), molecular biological and cellular functions are described in Table 3.
The present invention provides methods for the diagnosis of Alzheimer's disease using cells from subjects suspected of being at risk for developing AD or suspected of having AD. In the methods of the invention, the cells that are taken from the subject include any viable cells. In one embodiment, the cells are from peripheral tissues, i.e., non-neural tissue. In further specific embodiments, the tissue is skin, blood, mucosa, or cerebrospinal fluid.
In another specific embodiment, the cells are fibroblasts, epithethial cells, endothelial cells, or hematopoietic cells including lymphocytes. In a further specific embodiment, the cells are skin epithelial cells, skin fibroblast cells, blood cells or buccal mucosa cells. The cells may be fresh, cultured, or frozen prior to analysis. In a specific embodiment, a punch skin biopsy can be used to obtain skin fibroblasts from a subject. These fibroblasts are analyzed directly or introduced into cell culture conditions. In another specific embodiment, the cells are isolated from excised using laser capture microdissection to obtain a homogenous population of cells of the same type.
The method of the present invention contemplates using any compound known to have the ability to activate PKC. PKC activators are known in the art and include bradykinin, phorbol esters such as phorbol 12-myristate 13-acetate (PMA), phorbol 12,13-dibutyrate (PDBu), phorbol 12,13-didecanoate (PDD), bombesin, cholecystokinin, thrombin, prostaglandin F2α and vasopressin. Other PKC activators include natural and unnatural diacylglycerols (DAG), including diacylglycerols with various fatty acids in the 1,2-sn configuration are active. In a specific embodiment, the DAG contains an unsaturated fatty acid. In one embodiment, the PKC activator is a macrocyclic lactone, including but not limited to those in bryostatin compound class and neristatin compound class. In another embodiment, the PKC activator is a benzolactam. In a further embodiment, the PKC activator is a pyrrolidinone. In a specific embodiment, the macrocyclic lactone is bryostatin. In a more specific embodiment, the bryostatin is bryostatin-1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16, -17, or- 18.
The present invention also contemplates diagnoses of AD by detecting changes in gene expression in cells contacted with PKC activators selective for a specific isoform or isoforms of PKC. For example, benzolactam activates PKC α, β and γ. Bryostatin-1 selectively activates PKCα. Bradykinin activates PKCα, -δ, and -ζ. PKCε and η have been showed to be activated upon the administration of nitric oxide donors such as diethylenetriamine/NO (DETA/NO) and S-nitroso-N-acetylpenicillamine (SNAP) diethylenetriamine/NO (DETA/NO) and S-nitroso-N acetylpenicillamine (SNAP) (Balafanova et al., J. Biol. Chem. 2002; 277(17): 15021-15027). More recently, polyunsaturated fatty acid derivatives have been shown to selectively activate PKCε.
Exemplary concentrations of PKC activators that can be used to stimulate cells according to the methods of the present invention at a range of about 0.01 nM to 100 μM, preferably, 0.5 nM to 10 μM, more preferably 1 nM to 1 μM, and most preferably 10 nM to 500 nM.
Methods of evaluating changes in gene expression are well known in the art. The present invention contemplates both low-throughput methods such as Northern Blotting, in situ hybridization, and reverse transcription quantitative polymerase chain reaction (RVQ-PCR), and high-throughput methods such as microarrays and SAGE to detect differential gene expression. Preferably, detection is conducted using automatic, computerized equipment in a high-throughput setting, such as microarray technology. Such high-throughput equipment are commercially available, and techniques are well-known in the art.
In one specific embodiment, the method of the present invention provides detecting the gene transcript such as mRNA, including microRNA, cDNA or cRNA. The transcript can be from both coding and non-coding regions of the gene. The transcript can be detected in situ in the cell or in purified form extracted from the cell. In a specific embodiment, the nucleic acid is isolated and purified from the cell and then used in the gene expression assay.
In another embodiment, the method of the present invention provides detecting the protein product, or portion thereof, expressed from a gene transcript. Protein-based assays are also well-known in the art and include low-throughput methods such as Western blotting and ELISA, and high throughput protein microarrays.
In a further embodiment, the method of the present invention further comprises detecting the activity or activation state of the detected protein product, such as the phosphorylation of given protein.
In a specific embodiment of the invention, gene transcripts (e.g., cDNAs) from two different cells are hybridized to the binding sites of known gene transcripts on a microarray, one which is the test cell that has been stimulated with PKC activator and another the control cell, preferably of the same cell type, which has been stimulated with a PKC activator, preferably the same PKC activator. The nucleic acid derived from each of the two cell types are differently labeled so that they can be distinguished. Use of microarrays to evaluate differentially expressed transcripts are well known. See, e.g., U.S. Pat. No. 6,973,388. This technique typically involves preparing or purchasing microarrays containing known cDNA transcripts, extracting and labeling RNA from test cells, hybridizing the test RNA to the array, detecting and visualizing signal, performing statistical analysis on the results, and, optionally, validating the microarray results using low-throughput techniques.
Pre-made cDNA microarrays are commercially available from e.g., Affymetrix® (Santa Clara, Calif.), Agilent Technologies® (Santa Clara, Calif.) and AlphaGene® (Woburn, Mass.). These include whole genome arrays and targeted subsets of known genes.
In another specific embodiment, differential expression of genes is detected using serial analysis of gene expression (SAGE). SAGE quantitatively determines the amount of times a small portion of a specific mRNA transcript is expressed (a tag). The output of SAGE is a list of short sequence tags and the number of times it is observed. The major difference between microarray hybridization and serial analysis of gene expression (SAGE) techniques is that the latter does not require prior knowledge of the sequences to be analyzed; SAGE is a sequencing-based gene expression profiling technique.
In one embodiment of the invention, the test cells will demonstrate an observable difference in the level of expression of one or more genes compared with the level of expression of the same gene or genes in the control cells. In a specific embodiment, the differential expression is quantitative. In a further embodiment, the level gene expression detected in the test cells is about 1-fold, 2-fold, 5-fold, 10-fold and 100-fold upregulated or downregulated compared to the control cells.
In yet a further aspect, this invention relates to methods of screening therapeutic substances for the treatment or prevention of AD using the diagnostic tests described herein. According to this embodiment, compounds which reverse or improve the observed differences in gene expression described herein (i.e. back to or toward levels found in PKC-activated control cells) would be identified and selected as a substance potentially useful for the treatment or prevention of AD.
In one embodiment, the screening method comprises the steps of contacting cells from a subject that has been diagnosed with AD with a test compound for a period of time, followed by contacting the cells with an agent that is a PKC activator, and determining whether the test compound alters the differential expression of the genes identified according to the methods of the present invention towards levels observed in control cells from normal subjects.
In a specific embodiment, the cells contacted with the test compound are derived from a subject diagnosed with AD according to the methods of the present invention.
This invention also relates to kits comprising products useful for carrying out the diagnostic methods of the invention. The kits may also include instruments, buffers and storage containers necessary to perform one or more biopsies, such as punch skin biopsies. The kits can include high-density oligonucleotide arrays, reagents for use with the arrays, signal detection and array-processing instruments, gene expression databases and analysis and database management software. The kits may also contain instructions relating to the identification of differentially expressed genes used for the AD diagnosis.
As stated previously, the kits may contain a single diagnostic test or any combination of the tests described herein. All of the differences disclosed herein between control and AD cells form the basis for the clinical tests and diagnostic kits for AD disease diagnosis, as well as the methods of screening compounds for treatment or prevention of AD disclosed herein.
It is contemplated that the diagnostic methods of the present invention may be used in combination with any other diagnostic methods. Exemplary methods include physical and neurological evaluation; biomarker detection; and structural (MRI, CT) and functional brain imaging (PET; FDG-PET).
As one example, the methods of the present invention can be used in combination with evaluating mutations in the genes known to be involved in Familial AD. Additional methods of diagnosing AD are described in U.S. Pat. Nos. 6,080,582 and 6,300,085 to Alkon et al., which methods detect the absence of potassium ion channels in the cells of an AD patient, differences in intracellular calcium ion concentration in AD and non-AD cells in response to potassium channel blockers specific for the potassium ion channel that is absent in the cells of an AD patient, and differences between AD and non-AD cells in response to activators of intracellular calcium release such as activators of inositol-1,4,5-trisphosphate (IP3). Additional diagnostic methods are described in application publication number WO2007/047029 to Alkon et al. directed to diagnosing AD in a subject by detecting alterations in the ratio of specific phosphorylated MAP kinase proteins (Erk1/Erk 2) in cells after stimulation with a PKC activator. See also, Zhao et al., Neurobiol Dis. October 2002; 11(1):166-83.
This example describes the identification of differentially-expressed genes in AD cells according to the method of the present invention.
Bradykinin (BK; molecular weight, 1,060.2) was purchased from Calbiochem (San Diego, Calif.).
Skin Fibroblast Cell Culture. Human skin fibroblast cell culture systems were used for these studies. Banked skin fibroblasts cells with the diagnoses AD and age-matched control from the Coriell Institute of Medical Research were cultured (supplemented with 10% serum and penicillin/streptomycin) at 37° C. with 5% CO2 to the 90-100% confluence stage in 25-ml cell culture flasks. Cells were “starved” in serum-free medium (DMEM) for 24 h. A solution of 10 nM BK (in DMSO) was prepared in DMEM with 10% serum. Seven milliliters of the 10 nM BK solution was added to the culture flasks and incubated at 37° C. for 10 min. For the controls, the same amount of DMSO was added in DMEM with 10% serum. Seven milliliters of this medium with DMSO (<0.01%) was added to the culture flasks and incubated at 37° C. for 10 min. After washing four times with cold (4° C.) 1×PBS, flasks were kept in a dry ice/ethanol mixture for 15 min. Flasks were then removed from the dry ice/ethanol mixture, and the cells were treated with trypsin-EDTA (Invitrogen), centrifuged 400×g for 5 min, and the pellets were washed twice in PBS. The pellets were then quickly frozen in ethanol-CO2 ice and transferred to −70° C.
Total RNA was then isolated from the cultured fibroblast pellets using an RNeasy mini kit (Qiagen, Hilden, Germany) according to the manufacturer's protocol, which typically a yield of 5-10 μg of RNA per 106 cells. Nucleic acid was extracted from the cells according to standard procedures.
Microarray Analysis. For microarray probing, reverse transcription, second-strand synthesis, and probe generation were performed according to the GeneChip Expression Analysis Technical Manual (Affymetrix, Santa Clara, Calif.). The generated probe was subjected to hybridization to oligonucleotide DNA chips, Human Genome U133A (Affymetrix). The arrays were scanned with a GeneArray Scanner (Hewlett-Packard). Image Analysis and Data Quality Control. Scanner output image files were normalized and filtered by using MICROARRAY SUITE 5.0 software (Affymetrix). Normalization was performed by global scaling, with the arrays scaled to an arbitrary signal intensity value of 100. The detection metric (Presence or Absence calls) and decision of significant gene expression for a particular gene (probe set) was determined by using default parameters in the MICROARRAY SUITE 5.0 software.
Table 1 shows the genes down-regulated in AD cell lines following bradykinin stimulation but either activated or unchanged following bradykinin stimulation in age matched controls. Table 2 shows the genes up-regulated in AD cell lines following bradykinin stimulation but either down-regulated or unchanged following bradykinin stimulation in age matched controls. Table 3 provides the specific genes and their relationship(s), and molecular biological and cellular functions.
Homo sapiens adaptor protein with pleckstrin homology and src
Homo sapiens , KIAA1080 protein; Golgi-associated, gamma-adaptin
Homo sapiens sodium channel, voltage-gated, type I, beta polypeptide
Homo sapiens phosphoserine phosphatase-like (PSPHL), mRNA.
Homo sapiens hypothetical protein FLJ12455 (FLJ12455), mRNA.
Homo sapiens protein kinase, AMP-activated, beta 2 non-catalytic
Homo sapiens similar to CG9578 gene product (MGC3794), mRNA
Homo sapiens paired mesoderm homeo box 1 (PMX1), transcript
Homo sapiens ATPase, Ca++ transporting, plasma membrane 4
Homo sapiens full length insert cDNA clone
Homo sapiens forkhead box F2 (FOXF2), mRNA.
Homo sapiens clone FBD3 Cri-du-chat critical region mRNA
Homo sapiens nuclear autoantigen (GS2NA), mRNA. /
Homo sapiens Ste-20 related kinase (SPAK), mRNA.
Homo sapiens eukaryotic translation initiation factor 4 gamma, 3
Homo sapiens chromosome condensation protein G (HCAP-G),
Homo sapiens RBP1-like protein (BCAA), mRNA.
Homo sapiens , Similar to RIKEN cDNA 1700073K01 gene, clone
Homo sapiens mRNA for TGF-betaIIR alpha, complete cds.
Homo sapiens cDNA FLJ33255 fis, clone ASTRO2005553.
Homo sapiens ubiquitin specific protease 8 (USP8), mRNA.
Homo sapiens hypothetical protein FLJ10461 (FLJ10461), mRNA.
norvegicus]
The foregoing demonstrates that PKC-activation elicits different genomic profiles in AD cells, as compared with control cells, which can be used to diagnose AD and individuals at risk for developing AD.
Patents, patent applications, publications, product descriptions, and protocols are cited throughout this application, the disclosures of which are incorporated herein by reference in their entireties for all purposes.
This application claims the benefit of U.S. provisional application Ser. No. 61/084,154, filed on Jul. 28, 2008, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61084154 | Jul 2008 | US |
