Association of IRGM Gene Mutations with Inflammatory Bowel Disease in the Indian Population

BACKGROUND Mutations in the IRGM gene have been associated with Crohn's disease in several populations but have not been explored in Indian patients with this disease. This study examined the association of IRGM mutations with ulcerative colitis and Crohn's disease in Indian patients with inflammatory bowel disease. METHODS The IRGM gene was amplified in four segments and Sanger-sequenced in 101 participants (42 Crohn's disease, 39 ulcerative colitis, and 20 healthy controls). Ten single nucleotide polymorphisms (SNP) were genotyped in 1200 participants (352 Crohn's disease, 400 ulcerative colitis, and 448 healthy controls) using Sequenom MassARRAY iPLEX. Disease associations were evaluated for each of the ten SNPs. RESULTS Thirty one mutations were identified in the IRGM gene, of which two had not hitherto been reported (150226250- ss947429272 & 150227858- ss947429273). Ten SNPs (6 from the above and 4 from the literature) were evaluated. Significant associations with Crohn's disease were noted with the T allele of rs1000113 (OR 1.46, 95% CI 1.12-1.90), T allele of rs9637876 (OR 1.25, 95% CI 1.005-1.561) and C allele of rs 13361189 (OR 1.33, 95% CI 1.07-1.669). Two SNPs--rs11747270 and rs180802994--did not exhibit Hardy-Weinberg equilibrium but were associated with both Crohn's disease and ulcerative colitis in this population. The remaining SNPs did not show significant associations with either Crohn's disease or ulcerative colitis. CONCLUSIONS Association of IRGM gene SNPs with Crohn's disease is reported for the first time in Indian patients. We also report, for the first time, an association of rs 9637876 in the IRGM gene with Crohn's disease.