Genetic Studies of Inflammatory Bowel Disease

Using epidemiological, statistical, and molecular genetic techniques, this proposal is designed to investigate the existence of genetic regions that are believed to confer a risk for inflammatory bowel disease (IBD), which consists of two subtypes, Crohn's disease (CD) and ulcerative colitis (UC). The project will derive its study population, consisting of IBD physician confirmed affected probands with their family members, from the Johns Hopkins University, the University of Chicago, and the University of Pittsburgh. The project will consist of multiple parts. The first part is a reanalysis of existing genome wide linkage data from IBD families with 377 genotyped microsatellite marker data that incorporates covariate data into the analysis, with the goal of identifying new and refining previously identified regions of linkage. Eventually this may be extended to include new families typed for genome wide scan markers. The second part of the project consists of the fine mapping of the IBD3 locus (HLA region on chromosome 6p), which has been shown to have evidence of linkage in UC patients. Fifty-two microsatellite markers spanning the affected child trios in an effort to identify potential marker alleles that may be associated with UC, using the IBD3 locus will be genotyped in a study population consisting of 240 UC father-mother-affected child trios in an effort to identify potential marker alleles that may be associated with UC, using the transmission disequilibrium test, and to identify potential haplotypes that may confer an increased risk of developing UC, using a likelihood-based approach where a moving window of adjacent markers will be tested for excessive transmission. Additional candidate genes within IBD3 will be examined, and polymorphisms will also be tested for potential significant associations. Eventually this second part may be extended to fine mapping and association analysis of other candidate genes and/or candidate regions.