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Distinct and overlapping genetic loci in Crohn's disease and ulcerative colitis: correlations with pathogenesis.

ABSTRACT: A common genotypic basis for ulcerative colitis (UC) and Crohn's disease (CD) is implied by overlapping clinical characteristics, epidemiological studies, and association of genes with both UC and CD. We evaluated the overlap between CD and UC genetic loci stratified by pathogenetic pathways and by disease location.The allele frequencies of six UC-associated and 34 CD-associated single nucleotide polymorphisms (SNPs) were determined in a Canadian IBD cohort (n = 2374). Differences between CD, UC, colon-only CD, ileal CD, and controls were analyzed controlling for ethnicity, age of diagnosis, and gender.In all, 21 of 34 CD-associated SNPs had similar allele frequencies in UC (n = 1230) and CD (n = 1144). Three of six UC-associated SNPs had significantly different frequencies in CD (n = 1144). Most of the divergence in allele frequency among CD and UC was noted in NOD2/autophagy pathway SNPs, while most SNPs with similar frequencies were in IL-22/23 Th17, adaptive immunity, and barrier pathways. Colon-only CD (n = 228) was compared with healthy controls: three of six UC SNPs (in MST1, HLA-DRA, and IL-23R) and 11 of 34 CD SNPs: in IRGM, NOD2 (rs2066845), CCNY, MST1, IL23R, PTPN22, C11orf30, ZNF365, PTPN2, PSMG1, and rs1456893 were significantly associated. In all, 29 of 34 CD SNPs had similar allele frequencies in colonic CD compared with ileal CD (n = 366). All UC SNPs had similar frequencies in UC and colonic CD.Our results suggest that CD and UC share common genetic associations related to impaired adaptive immunity and diverge in pathways of foreign antigen processing. Colon-only CD overlaps extensively with UC and considerably with ileal CD.

SUBMITTER: Waterman M

PROVIDER: S-EPMC3164287 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Distinct and overlapping genetic loci in Crohn's disease and ulcerative colitis: correlations with pathogenesis.

Waterman Matti M Xu Wei W Stempak Joanne M JM Milgrom Raquel R Bernstein Charles N CN Griffiths Anne M AM Greenberg Gordon R GR Steinhart A Hillary AH Silverberg Mark S MS

Inflammatory bowel diseases 20101210 9

<h4>Background</h4>A common genotypic basis for ulcerative colitis (UC) and Crohn's disease (CD) is implied by overlapping clinical characteristics, epidemiological studies, and association of genes with both UC and CD. We evaluated the overlap between CD and UC genetic loci stratified by pathogenetic pathways and by disease location.<h4>Methods</h4>The allele frequencies of six UC-associated and 34 CD-associated single nucleotide polymorphisms (SNPs) were determined in a Canadian IBD cohort (n ...[more]

PMID: 21830272

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Project description:BackgroundCrohn's disease and ulcerative colitis are the two major forms of inflammatory bowel disease; treatment strategies have historically been determined by this binary categorisation. Genetic studies have identified 163 susceptibility loci for inflammatory bowel disease, mostly shared between Crohn's disease and ulcerative colitis. We undertook the largest genotype association study, to date, in widely used clinical subphenotypes of inflammatory bowel disease with the goal of further understanding the biological relations between diseases.MethodsThis study included patients from 49 centres in 16 countries in Europe, North America, and Australasia. We applied the Montreal classification system of inflammatory bowel disease subphenotypes to 34,819 patients (19,713 with Crohn's disease, 14,683 with ulcerative colitis) genotyped on the Immunochip array. We tested for genotype-phenotype associations across 156,154 genetic variants. We generated genetic risk scores by combining information from all known inflammatory bowel disease associations to summarise the total load of genetic risk for a particular phenotype. We used these risk scores to test the hypothesis that colonic Crohn's disease, ileal Crohn's disease, and ulcerative colitis are all genetically distinct from each other, and to attempt to identify patients with a mismatch between clinical diagnosis and genetic risk profile.FindingsAfter quality control, the primary analysis included 29,838 patients (16,902 with Crohn's disease, 12,597 with ulcerative colitis). Three loci (NOD2, MHC, and MST1 3p21) were associated with subphenotypes of inflammatory bowel disease, mainly disease location (essentially fixed over time; median follow-up of 10·5 years). Little or no genetic association with disease behaviour (which changed dramatically over time) remained after conditioning on disease location and age at onset. The genetic risk score representing all known risk alleles for inflammatory bowel disease showed strong association with disease subphenotype (p=1·65 × 10(-78)), even after exclusion of NOD2, MHC, and 3p21 (p=9·23 × 10(-18)). Predictive models based on the genetic risk score strongly distinguished colonic from ileal Crohn's disease. Our genetic risk score could also identify a small number of patients with discrepant genetic risk profiles who were significantly more likely to have a revised diagnosis after follow-up (p=6·8 × 10(-4)).InterpretationOur data support a continuum of disorders within inflammatory bowel disease, much better explained by three groups (ileal Crohn's disease, colonic Crohn's disease, and ulcerative colitis) than by Crohn's disease and ulcerative colitis as currently defined. Disease location is an intrinsic aspect of a patient's disease, in part genetically determined, and the major driver to changes in disease behaviour over time.FundingInternational Inflammatory Bowel Disease Genetics Consortium members funding sources (see Acknowledgments for full list).

Dataset Information

Distinct and overlapping genetic loci in Crohn's disease and ulcerative colitis: correlations with pathogenesis.

Publications

Distinct and overlapping genetic loci in Crohn's disease and ulcerative colitis: correlations with pathogenesis.

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