Characterization of genetic loci that affect susceptibility to inflammatory bowel diseases in African Americans.
Huang C, Haritunians T, Okou DT, Cutler DJ, Zwick ME, Taylor KD, Datta LW, Maranville JC, Liu Z, Ellis S, Chopra P, Alexander JS, Baldassano RN, Cross RK, Dassopoulos T, Dhere TA, Duerr RH, Hanson JS, Hou JK, Hussain SZ, Isaacs KL, Kachelries KE, Kader H, Kappelman MD, Katz J, Kellermayer R, Kirschner BS, Kuemmerle JF, Kumar A, Kwon JH, Lazarev M, Mannon P, Moulton DE, Osuntokun BO, Patel A, Rioux JD, Rotter JI, Saeed S, Scherl EJ, Silverberg MS, Silverman A, Targan SR, Valentine J, Wang MH, Simpson CL, Bridges SL, Kimberly RP, Rich SS, Cho JH, Di Rienzo A, Kao LW, McGovern DP, Brant SR, and Kugathasan S. Characterization of genetic loci that affect susceptibility to inflammatory bowel diseases in African Americans. Gastroenterology 2015; 149(6):1575-1586.
BACKGROUND & AIMS: Inflammatory bowel disease (IBD) has familial aggregation in African Americans (AAs), but little is known about the molecular genetic susceptibility. Mapping studies using the Immunochip genotyping array expand the number of susceptibility loci for IBD in Caucasians to 163, but the contribution of the 163 loci and European admixture to IBD risk in AAs is unclear. We performed a genetic mapping study using the Immunochip to determine whether IBD susceptibility loci in Caucasians also affect risk in AAs and identify new associated loci.
METHODS: We recruited AAs with IBD and without IBD (controls) from 34 IBD centers in the United States; additional controls were collected from 4 other Immunochip studies. Association and admixture loci were mapped for 1088 patients with Crohn's disease, 361 with ulcerative colitis, 62 with IBD type unknown, and 1797 controls; 130,241 autosomal single-nucleotide polymorphisms (SNPs) were analyzed.
RESULTS: The strongest associations were observed between ulcerative colitis and HLA rs9271366 (P = 7.5 × 10(-6)), Crohn's disease and 5p13.1 rs4286721 (P = 3.5 × 10(-6)), and IBD and KAT2A rs730086 (P = 2.3 × 10(-6)). Additional suggestive associations (P < 4.2 × 10(-5)) were observed between Crohn's disease and IBD and African-specific SNPs in STAT5A and STAT3; between IBD and SNPs in IL23R, IL12B, and C2orf43; and between ulcerative colitis and SNPs near HDAC11 and near LINC00994. The latter 3 loci have not been previously associated with IBD, but require replication. Established Caucasian associations were replicated in AAs (P < 3.1 × 10(-4)) at NOD2, IL23R, 5p15.3, and IKZF3. Significant admixture (P < 3.9 × 10(-4)) was observed for 17q12-17q21.31 (IZKF3 through STAT3), 10q11.23-10q21.2, 15q22.2-15q23, and 16p12.2-16p12.1. Network analyses showed significant enrichment (false discovery rate
CONCLUSIONS: In a genetic analysis of 3308 AA IBD cases and controls, we found that many variants associated with IBD in Caucasians also showed association evidence with these diseases in AAs; we also found evidence for variants and loci not previously associated with IBD. The complex genetic factors that determine risk for or protection against IBD in different populations require further study.
Medical Subject Headings
Adult; African Americans; Aged; Colitis, Ulcerative; Crohn Disease; European Continental Ancestry Group; Female; Genetic Loci; Genetic Predisposition to Disease; Humans; Inflammatory Bowel Diseases; Male; Middle Aged; Polymorphism, Single Nucleotide; Risk Factors; United States; Young Adult