DIAGNOSTIC MICROARRAY FOR INFLAMMATORY BOWEL DISEASE, CROHN'S DISEASE AND ULCERATIVE COLITIS
Elizabeth E. Mannick, Zhiyun Liu, and Maria-stella Serrano
Express Mail No. EF199471513 File No. 00M31.2-PCT Mannick
The benefit of the filing dates of provisional applications 60/286,602 filed April 26, 2001, 60/264,909 filed January 29, 2001, and 60/250,303 filed November 30, 2000 are claimed under 35 U.S.C. § 119(e) in the United States, and are claimed under applicable treaties and conventions in all countries.
TECHNICAL FIELD This invention pertains to a method that uses DNA microarray hybridization to identify patients with inflammatory bowel disease, and to distinguish Crohn's disease from ulcerative colitis.
BACKGROUND ART Despite greater than fifty years of clinical experience with Crohn's disease and ulcerative colitis, collectively known as inflammatory bowel disease (TBD), the precise etiology of these diseases remains unknown and the morbidity they engender high. Further, between 10-15% of patients cannot be accurately diagnosed as having either Crohn's disease or ulcerative colitis and are classified as indeterminate colitis, making treatment decisions and evaluation of long-term prognosis difficult.
IBD susceptibility loci have recently been mapped to chromosomes 1, 3, 4, 6, 10, 12, 16, X and 22. See J.P. Hugot et al., "Genome-wide scanning in inflammatory bowel diseases," Dig. Dis., vol. 16, pp. 364-369 (1998); J. Hampe et al., "A genomewide analysis provides evidence for novel linkages in inflammatory bowel disease in a large European cohort," Am. J. Hum. Genet., vol. 64, pp. 808-816 (1999); and K.G. Becker et al., "Clustering of non-major histocompatibility complex susceptibility candidate loci in human autoimmune
diseases," Proc. Natl. Acad. Sci. USA, vol. 95, pp. 9979-9984 (1998). Due to the painstaking nature of linkage analysis and positional cloning techniques, no IBD candidate gene has as yet been identified.
The current revolution in molecular genetics offers new hope of identifying genes that may play a role in disease susceptibility, etiology, and diagnosis. Microarray gene analysis has recently been added to the arsenal of molecular genetic techniques. See M. Schena et al., "Qualitative monitoring of gene expression patterns with a complementary DNA microarray," Science, vol. 270, pp. 467-470 (1995). Microarray analysis allows an investigator to screen for thousands of genes in a relatively small patient sample such as a single endoscopic biopsy or a small amount of blood (< 2 cc). A microarray is a glass slide, microchip, or membrane with cDNA of thousands of known sequences spotted on it. These microarrays then serve as sequence targets for hybridization to cDNA probes prepared from RNA samples from cells or tissues. A two-color fluorescence labeling technique is generally used in the preparation of the cDNA probes such that a simultaneous hybridization, but separate detection of signals, provides a comparative analysis and a determination of the relative abundance of specific genes expressed. Microarrays can be constructed from specific cDNA clones of interest, a cDNA library, or a select number of open-reading frames from a genome sequencing database to allow a large-scale functional analysis of expressed sequences. See R.A. Heller et al., "Discovery and analysis of inflammatory disease-related genes using cDNA microarrays," Proc.Natl.Acad.Sci.USA, vol. 94, pp. 2150-2155 (1997); and M. Schena et al, "Quantitative Monitoring of Gene Expression Patterns with a Complementary DNA Microarray," Science, vol. 270, pp. 467-470 (1995). An advantage of microarray technology is that more than one oligonucleotide sequence per gene may be included on the array, potentially providing greater specificity. Microarray analysis offers a complementary approach to gene mapping strategies.
However, the diagnostic genes identified by microarray analysis may be different from the genes found by positional cloning, because the occurrence of RNA in the sample used for the microarray analysis may be influenced by environmental factors, including medical treatments, that induce or suppress genetic expression. Microarray analysis using selected human sequences of probable significance in inflammation, as well as with sequences expressed in peripheral human blood cells, has been used to compare gene expression in tissue samples of rheumatoid arthritis (late stage
rheumatoid synovial tissue) and inflammatory bowel disease (inflamed lower intestinal mucosa of patients with Crohn's disease). See Heller et al., 1997.
Samples from the mucosal intestinal wall of ulcerative colitis and Crohn's disease patients with inflamed and noninflamed controls have been used in a microarray analysis of approximately 6000 sequences (Affymetrix GeneChip). See B.K. Dieckgraefe et al., "Analysis of mucosal gene expression in inflammatory bowel disease by parallel oligonucleotide arrays," Physiol. Genomics, vol. 4, pp. 1-11 (2000); I. Lawrence, C. Fiocchi, S. Chakravarti, "Ulcerative colitis and Crohn's disease: distinctive gene expression profiles and novel susceptibility candidate genes." Hum Mol Genet 2001;10:445-56; and International Application No. WO 01/29269 A2.
DISCLOSURE OF INVENTION
We have discovered, using RNA samples from mononuclear blood cells, gene sequences that can be used to identify patients with IBD, Crohn's disease, and ulcerative colitis. Sequences were identified whose over- or underexpression was distinct to patients with IBD, Crohn's disease, or ulcerative colitis when compared to patients with non-IBD intestinal disorders. Additionally, cluster analysis was used to identify twenty-five sequences that are IBD-related, and whose transcription pattern can be used in a microarray analysis to identify patients with IBD with a sensitivity of 84% and a specificity of 100%. Cluster analysis also identified thirty-six genes that could be used to distinguish patients with Crohn's disease from those with ulcerative colitis with a sensitivity of 80% and a specificity of 89%.
MODES FOR CARRYING OUT THE INVENTION
The microarray information on over- and under-expression of gene sequences can be used to develop diagnostic tests for Crohn's disease, ulcerative colitis and inflammatory bowel disease. It can be used to identify subcategories of patients in order to predict disease prognosis. For example, Crohn's disease is subclassifed into fibrostenosing and inflammatory subtypes, which may correspond to genotypic as well as phenotypic differences. It can also be used to monitor the results of drug therapy for inflammatory bowel disease, ulcerative colitis and Crohn's disease. Finally, it has the potential to be used to identify drug targets in order to develop new therapies for the treatment of inflammatory bowel disease. For example, an overexpressed gene that is secreted and/or membrane-bound, if overexpressed at the protein level, could be targeted with a monoclonal antibody. Two genes
identified here that are overexpressed in patients with inflammatory bowel disease, antigen CD36 (clone 13), and APRIL protein, might serve as targets for monoclonal antibody therapy. Alternatively, underexpressed genes, such as G protein-gamma 4, ARC34, SHPS-1 or carbonic anhydrase π, which, based on their biological function, could play a role in IBD pathogenesis, could be targets for replacement with gene therapy. For a review of the use of microarray data for prognostic, pharmacotherapy monitoring and drug discovery uses, see S. Braxton et al., "The integration of microarray information in the drug development process," Curr. Opin. BiotechnoL, vol. 9, pp. 643-649 (1988); and G. I. Adam et al, "Pharmacogenomics to predict drug response," Pharmacogenomics, vol. 1, pp. 5-14 (2000); and S.F. Grant, "Pharmacogenetics and pharmacogenomics: tailored drug therapy for the 21st century," Trends Pharmacol. Sci., vol. 22, pp. 3-4 ( 2001).
Example 1
Identification of Overexpressed and Underexpressed Genes in Patients with Crohn 's Disease
A genetic study was completed using microarray analysis to compare the expression of 2400 sequences in peripheral blood mononuclear cells ("PBMC") from 14 patients with Crohn's disease as compared to 10 healthy, age-matched controls. A MICROMAX™ Human cDNA Microarray System was obtained from NEN Life Sciences, Inc. (Boston, Massachusetts). The MICROMAX™ system comes with 2400 human sequences spotted on a glass slide. Except for a small number of plant control sequences, all sequences are from over 50 human cDNA libraries representing more than 10 tissue sources created by Alphagene, Incorporated (Woburn, Massachusetts). The list of sequences included on the microarray slide is available on the website for NEN Life Sciences, Inc., http://www.nen.com/products/gene-list5.txt. This system allows direct, quantitative comparison of gene expression between a test (e.g., patient) sample labeled with, for example, a red fluorescent dye and a control sample labeled with, for example, a green fluorescent dye, both hybridized on the same microarray slide. The ratio of red-to-green fluorescent intensity at each site represents the ratio of differential gene expression (after normalization for housekeeping genes and subtraction of background). Advantages of this system are the ability to hybridize samples from two groups under the same conditions, as well as the easy visualization ofthe results ofthe analysis.
Peripheral blood mononuclear cells (PBMC) were extracted from blood drawn from each patient and controls using Ficoll (Sigma, St. Louis, MO). Although ideally PBMC should be sorted by cell type (T cells, B cells, monocytes, dendritic cells, etc.), the amount of total extracted RNA was already at the lower limit for reliable detection. Follow-up flow cytometry experiments, will be conducted for genes of particular interest to identify the exact cellular sources ofthe over- or under-expressed genes.
RNA was extracted from PBMC using the Trisol method. Extracted RNA was purified using a phenol-chloroform extraction. See F. Ausubel et al., Short Protocols in Molecular Biology, 3rd Edition, Wiley & Company, pp. 2-3 (1995). RNA was measured by spectrophotometry, and 1.5 mg of RNA was run on a 1% agarose gel to assess RNA quality. RNA was converted to cDNA using reverse transcriptase (NEN Life Sciences, Inc.) in a thermocycler. During tins step, cDNA of the patient samples was labeled with dinitrophenol (DNP), and cDNA of the control samples with biotin. cDNA of each sample was then purified by ethanol precipitation, analyzed by dot blot using horseradish peroxidase (HRP). HRP-conjugated, anti-DNP antibody and streptavidin-HRP conjugate, and the total amount was estimated using known cDNA standards. All of the above procedures followed the detailed protocol of and used the reagents provided with the MICROMAX™ kit available from NEN Life Sciences, Inc.
Equal amounts of cDNA from a patient and from an age- and sex-matched control were combined and denatured in hybridization buffer (NEN Life Sciences, Inc.) at 90°C, and then hybridized on the glass slide microarray (NEN Life Sciences, Inc.) at 65 °C overnight. After washing in a sodium citrate-sodium chloride buffer (3M sodium chloride, 0.3m sodium citrate, ph 7.0) (NEN Life Sciences, Inc.) three times, the slides were blocked with normal goat serum, incubated with anti-DNP-HRP conjugate, followed by Cyanine 3 (red fluorescent) dye conjugated to tyramide for signal amplification. After rinsing and HRP inactivation, the slides were incubated with streptavidin-HRP conjugate, followed by Cyanine 5 (green fluorescent) dye conjugated to tyramide and rinsed. All of the above reagents were provided in the MICROMAX™ kit. After drying, slides were sent to NEN Life Sciences for laser scanning. A ratio of red-to-green (patient-to-control) fluorescent intensities was calculated after subtracting background intensity from the signal and normalizing for housekeeping sequences in the array.
The 14 patients ranged in age from 10 to 55; 6 had been treated for Crohn's disease and 8 were untreated, 10 were males and 4 female, 11 had active disease and 3 were in
remission. Table 1 is a list of the 25 sequences of the 2400 sequences assayed that were the most overexpressed and of the 25 sequences that were the most underexpressed in the fourteen Crohn's patients. The sequences are sorted by the median ratio after normalization of data by median centering each array. A median ratio of greater than 2 or less than 0.50 is often used to identify sequences of potential biological significance; i.e., genes that are overexpressed or underexpressed, respectively.
Table 1
Gene Expression in Fourteen Patients with Crohn's Disease
Example 2
Identification of Overexpressed and Underexpressed Genes in Patients with Ulcerative Colitis
A second genetic study was completed using microarray analysis to compare the expression of 2400 sequences in peripheral blood mononuclear cells ("PBMC") from 11 patients with ulcerative colitis as compared to 10 healthy, age-matched controls. Of the 11 patients with ulcerative colitis, 5 had active disease and 6 were inactive. Six were untreated, and five were being treated with some combination of steroids, immunosuppressive agents, and 5-ASA compounds. The procedure was as described in Example 1, using the MICROMAX™ Human cDNA Microarray System obtained from NEN Life Sciences, Inc. (Boston, Massachusetts). Table 2 is a list ofthe 25 sequences ofthe 2400 sequences assayed that were the most overexpressed and of the 25 sequences that were the most underexpressed
in the eleven UC patients. The sequences are sorted by the median ratio after normalization of data by median centering each array. A median ratio of greater than 2 or less than 0.50 is often used to identify genes of potential biological significance.
Table 2
Gene Expression in Ulcerative Colitis Patients
Example 3
Identification of Genes Whose Expression Indicates IBD, Crohn's Disease, or Ulcerative Colitis
Another microarray study was performed to compare gene expression in peripheral blood mononuclear cells from 14 patients with Crohn's, 11 patients with ulcerative colitis, and 10 patients with chronic intestinal inflammation unrelated to inflammatory bowel disease (Clostridium difficile colitis, celiac disease, Helicobacter pylori gastritis, food poisoning, disseminated Mycobacterial infection with gastrointestinal involvement, disseminated Histoplasmosis with gastrointestinal involvement, sarcoidosis with gastrointestinal involvement, colonic adenomatosis with diverticulosis, eosinophilic gastroenteritis/colitis, irritable bowel syndrome) ("non-IBD disease patients"), and 35 age- and sex-matched unaffected controls. This study used the same IBD patients as in Examples 1 and 2. This study was designed to identify specific genes whose expression pattern might be used to
diagnose patients with inflammatory bowel disease ("IBD"), and also to distinguish patients with Crohn's disease from those with ulcerative colitis. The RNA extraction and the microarray analysis were performed as described above in Example 1 using the MICROMAX™ Human cDNA Microarray System from NEN Life Sciences, Inc. (Boston, Massachusetts).
In order to identify IBD-specific genes, the following criteria were applied to the results obtained from scanning the microarray slides. Sequences were identified as IBD- related genes if the gene was overexpressed or underexpressed by a factor of two or more in at least 25% of the patients with either ulcerative colitis or Crohn's disease as compared to patients with chronic intestinal inflammation unrelated to IBD after normalization by median centering arrays. The genes listed in Table 3 met this criteria.
Table 3 also lists sequences specific for Crohn's disease and for ulcerative colitis (UC). Sequences were identified as Crohn' s-specific genes if the gene was overexpressed or underexpressed by a factor of 2 or more in at least 25% of patients with Crohn's disease as compared to patients with chronic intestinal inflammation unrelated to IBD.
Sequences were identified as UC-specific genes if the gene was overexpressed or underexpressed by a factor of 2 or more in at least 25% of patients with ulcerative colitis as compared to patients with other inflammatory gastrointestinal disorders.
Table 3:
IBD-Related Genes and Percent of Patients Over/Underexpressing
Additional sequences that were over- and underexpressed in patients with Crohn's disease were identified using significance analysis of the microarray data. These additional genes are listed in Table 4.
Table 4
Additional Under- and Over-Expressed Sequences in PBMC's from patients with Crohn's Disease
Additional sequences that were over- and underexpressed in patients with ulcerative colitis e were identified using significance analysis of the microarray data. These additional genes are listed in Table 5
Table 5
Additional Under- and Over-Expressed Sequences in PBMC's from patients with Ulcerative Colitis
Example 4 Diagnostic Array for Patients with IBD, Crohn 's Disease and Ulcerative Colitis Using the microarray data generated in Example 3, cluster analysis was performed to identify clusters of related genes that may be involved in disease processes using the Cluster Analysis software kindly provided by Michael Eisen on the internet (http://rana.stanford.edu/software) See M.B. Eisen et al., "Cluster analysis and display of genome-wise expression patterns," Proc. Natl. Acad. Sci. USA, vol. 95, pp. 14863-14868 (1998)
Cluster analysis indicated that by using 24 genes, IBD could be identified in our patient sample with a sensitivity of 84% and a specificity of 100%. By using 25 genes (the 24 genes plus one additional gene), IBD could be identified with a sensitivity of 88% and a specificity of 90%. The genes identified are the following: Acidic calponin (Acc# S80562), Beta-sarcoglycan A3b (Acc# U31116), CL100 mRNA for protein tyrosine phosphatase (Acc# X68277), ZIP-kinase (Acc# AB007144), G protein gamma-4 subunit (Acc# U31382), Fibroblast muscle-type tropomyosin (Acc# M12125), Alkali myosin light chain 1 (Acc# M20642), Achaete scute homologous protein (Acc# L08424), Sorting nexin 2 (SNX2) (Acc# AF043453), Tristetraproline (TTP) (Acc# M63625), serine/threonine protein kinase (#D86550) (Acc# U59305), KIAA0210 (Acc# D86965), Methionine aminopeptidase (Acc# U29607), (p23) (Acc# L24804), Placenta (Diff48) (Acc# U49187), Rac3 (RAC3) (Acc# AF008591), Jun-B (Acc# X51345), Tyrosine phosphatase (Acc# Z68092), Complement component C3 mRNA, alpha and beta subunits (Acc# K02765), PKC alpha (Acc# X52479), SHPS-1 (Acc# D86043), Hbrm (Acc# X72889), Maleylacetoacetate isomerase(Acc# AJ001838), mRNA encoding GPI-anchored protein pl37 (Acc# Z48042). The second cluster is composed of these 24 genes plus one additional gene, Homolog of Drosophila enhancer of split m9/mlO(Acc# U04241).
Additionally, cluster analysis indicated that by using thirty-six genes, patients with Crohn's disease could be distinguished from patients with ulcerative colitis with a sensitivity
of 89% and a specificity of 80% for Crohn's disease, and a sensitivity of 89% and specificity of 80% for ulcerative colitis. These thirty-six genes were identified as the following: ()) (Acc# L24804), (Acc# D21267); 14-3-3 protein epsilon isoform (Acc# U43399); 47 kD autosomal chronic granulomatous disease protein (Acc# M55067); Adaptor protein XII beta (Acc# AF047348); Adenylate kinase 2 (adk2) (Acc# U39945); Adenylyl cyclase-associated protein (CAP) (Acc# L12168); alpha-CPl (Acc# U24223); Apoptotic protease activating factor 1 (Apaf-1) (Acc# AF013263); cAMP-dependent protein kinase subunit RTI-beta (Acc# M31158); COX Nile gene for subunit Nile of cytochrome c oxidase (EC 1.9.3.1) (Acc# U53328); Arp2/3 protein complex subunit p34-Arc (ARC34) (Acc# AF006085); D53 (hD53) (Acc# M77830); Desmin (Acc# AF006012); Dynamin (DΝM) (Acc# S72422); H5; and platelet glycoprotein lb beta chain (Acc# U59632); Keratin, keratin 16 homolog (Acc# S72493); Lymph node homing receptor (Acc# M25280); Lysosomal-associated multitransmembrane protein (LAPTm5) (Acc# U51240); MHC protein homologous to chicken B complex protein (Acc# M24194); mRΝA for Clock (Acc# AB005535); mRΝA for lymphocte activation marker Blast- 1 (Acc# X06341); mRΝA for ORF (Acc# X80822); mRΝA for ZTP-kinase (Acc# AB007144); Myosin alkali light chain (ventricular) (Acc# M24122); Myosin light chain 3 non-muscle (MLC3nm) (Acc# M31212); Ν- acetylglucosaminyltransferase I (GlcΝAc-TI) (Acc# M55621); Νicotinic acetylcholine receptor alpha3 subunit precursor, (Acc# U62432); pl67 (Acc# U58046); P2xl receptor (Acc# U45448); Partial CI mRΝA (Acc# X78817); Protein-tyrosine kinase (JAKl) (Acc# M64174); rab2 mRΝA, YPTl-related and member of ras family (Acc# X12953); Retinoid X receptor beta (RXR-beta) (Acc# M84820); Sorbitol dehydrogenase gene (Acc# U07361); Wilm's tumor-related protein (QM) (Acc# M64241).
Using the above information, a microarray could be custom-made using cDΝAs ofthe above sequences, along with housekeeping sequences and plant or other control sequences. Such a custom-made microarray with cDΝA from fewer sequences than the original 2400 sequences would decrease the cost of using a microarray as a diagnostic tool for IBD. The microarray could include all genes identified for IBD, Crohn's, and UC as listed in Table 2. The better method would be a microarray that would contain the twenty-five sequences that can identify IBD, and the thirty-six sequences that could then distinguish Crohn's from ulcerative colitis. Such a microarray would contain the following sixty genes (because one sequence overlaps in the two lists): Acidic calponin (Acc# S80562), Beta-sarcoglycan A3b (Acc# U31116), CL100 mRΝA for protein tyrosine phosphatase (Acc# X68277), ZTP-kinase
(Acc# AB007144), G protein gamma-4 subunit (Acc# U31382), Fibroblast muscle-type tropomyosin (Acc# M12125), Alkali myosin light chain 1 (Acc# M20642), Achaete scute homologous protein (Acc# L08424), Sorting nexin 2 (SNX2) (Acc# AF043453), Tristetraproline (TTP) (Acc# M63625), serine/threonine protein kinase (#D86550) (Acc# U59305), KIAA0210 (Acc# D86965), Methionine aminopeptidase (Acc# U29607), (p23) (Acc# L24804), Placenta (Diff48) (Acc# U49187), Rac3 (RAC3) (Acc# AF008591), jun-B (Acc# X51345), tyrosine phosphatase (Acc# Z68092), Complement component C3 mRNA, alpha and beta subunits (Acc# K02765), PKC alpha (Acc# X52479), SHPS-1 (Acc# D86043), Hbrm (Acc# X72889), maleylacetoacetate isomerase(Acc# AJ001838), mRNA encoding GPI-anchored protein pi 37 (Acc# Z48042), Homolog of Drosophila enhancer of split m9/ml0 (Acc# U04241), (p23) (Acc# L24804), (Acc# D21267), 14-3-3 protein epsilon isoform (Acc# U43399); 47 kD autosomal chronic granulomatous disease protein (Acc# M55067); Adaptor protein XH beta (Acc# AF047348); Adenylate kinase 2 (adk2) (Acc# U39945); Adenylyl cyclase-associated protein (CAP) (Acc# L12168); alpha-CPl (Acc# U24223); Apoptotic protease activating factor 1 (Aρaf-1) (Acc# AF013263); cAMP- dependent protein kinase subunit RTJ-beta (Acc# M31158); COX NTJc gene for subunit Nile of cytochrome c oxidase (EC 1.9.3.1); (Acc# U53328); Arp2/3 protein complex subunit p34- Arc (ARC34) (Acc# AF006085); D53 (hD53) (Acc# M77830); Desmin (Acc# AP006012) Dynamin (DΝM) (Acc# S72422); H5; and platelet glycoprotein lb beta chain (Acc# U59632) Keratin, keratin 16 homolog (Acc# S72493); Lymph node homing receptor (Acc# M25280) Lysosomal-associated multitransmembrane protein (LAPTm5) (Acc# U51240); MHC protein homologous to chicken B complex protein (Acc# M24194); mRNA for Clock (Acc# AB005535); mRΝA for lymphocte activation marker Blast-1 (Acc# X06341); mRΝA for ORF (Acc# X80822); Myosin alkali light chain (ventricular) (Acc# M24122); Myosin light chain 3 non-muscle (MLC3nm) (Acc# M31212); Ν-acetylglucosaminyltransferase I (GlcΝAc-TI) (Acc# M55621); Νicotinic acetylcholine receptor alpha3 subunit precursor, (Acc# U62432); pl67 (Acc# U58046); P2xl receptor (Acc# U45448); Partial CI mRΝA (Acc# X78817); Protein-tyrosine kinase (JAKl) (Acc# M64174); rab2 mRΝA, YPTl-related and member of ras family (Acc# X12953); Retinoid X receptor beta (RXR-beta) (Acc# M84820); Sorbitol dehydrogenase gene (Acc# U07361); Wihn's tumor-related protein (QM) (Acc# M64241).
The following additional genes were identified as significant diagnostic genes for inflammatory bowel disease, Crohn's Disease, and ulcerative colitis: 2',3'-cyclic nucleotide3'- phosphodiesterase (Acc# Ml 9650), D53(hD53) (Acc# U44427), DΝA fragmentation factor-
45 (Acc# U91985), Drgl (Acc# X92845), Epidermal growth factor receptor substrate (epsl5) (Acc# U07707),Myosin heavy chain (Acc# M35230), ARL1 (Acc# L28997), Clone 22 mRNA, alternative splice variant beta-2 (AF009424), Glutathione-S-transferase homolog (Acc# U90313), Leukemia virus receptor 2 (Acc# L20852), Muscle specific enolase (Acc# X51957), Type 3 inositol 1,4,5-triphosphate receptor (D26351), Hrs (Acc# D84064).
Example 5 Confirmation of Gene Expression
Studies to confirm the expression of 10 disease-related genes identified above will be performed. Preliminary analysis or 7 disease-related genes have been confirmed. These studies used SYBR green real-time PCR on RNA stored from the initial PBMC extraction. SYBR green real-time PCR involves the introduction of a SYBR green dye that fluoresces when bound to double-stranded (ds) DNA. During amplification, fluorescent measurements were taken and a threshold cycle (C() value for each sample was calculated to determine the cycle time at which the fluorescent intensity exceeded a threshold (10 times the standard deviation from baseline emissions). Threshold cycle, or sample positivity, was directly proportional to the amount of target material allowing quantization of gene expression. Primers designed for the genes of interest was designed and tested for primer stability using ABI Primer Express software (Applied Biosystems, Foster City, CA) and synthesized by Integrated DNA technologies (Coral Nille, Iowa). Briefly, reverse transcription of lOOng of RΝA was performed using Rnase H-deficient reverse transcriptase (Superscript TJ, Life Technologies, Rockville, Maryland) and Random Hexamer primers. The PCR reaction was performed using the Taq-Man Core PCR kit (PE Applied Biosystems) in 96-well trays with optical caps containing triplicates of each sample. The reaction mixture was generally preheated for 10 minutes at 95°C, then 35 cycles of 15 seconds at 95°C and one minute at 60°C, followed by one cycle of heating from 60°C to 95°C over 20 minutes to obtain a melting curve ofthe PCR products and carried out by a 7700 Sequence Detector (PE Applied Biosystems). PCR conditions for each of the overexpressed and underexpressed genes was optimized including primer concentration and magnesium concentration. The relative gene expression is determined based on the normalized threshold cycle ofthe gene of interest to a pool of unaffected control samples to control for transcription efficiency. The normalized Ct value obtained for each gene for IBD samples was compared with the value obtained for each gene for unaffected control samples. Ratios of relative gene expression are then compared
with microarray results. Preliminary results confirmed relative expression for the following seven genes: Acidic Calponin (Accession #S80562), Arp 2/3 protein complex subunit 34-Arc (ARC34) (Accession #AF006085), Human antigen CD36 (clone 13) mRNA (Accession #M98398), Human epidermal growth factor receptor substrate (epsl5) (Accession #U07707), mRNA for Hrs (Accession #D84064), Serine threonine kinase 11 (STKll) (Accession #AF035625), and mRNA for SHPS-1 (Acc# D86043).
The complete disclosures of all references cited in this specification are hereby incorporated by reference. Also incorporated by reference is the full disclosure of the following poster: M.-S. Serrano et al., "Application of microarray analysis to Crohn's disease," World Congress of Pediatric Gastroenterology and Nutrition, Boston, Massachusetts, August 7, 2000. In the event of an otherwise irreconcilable conflict, however, the present specification shall control.