Vitamin D receptor gene polymorphism: association with Crohn's disease susceptibility

Abstract

BACKGROUND: The vitamin D receptor (VDR) gene represents a strong positional candidate susceptibility gene for inflammatory bowel disease (IBD). The VDR gene maps to a region on chromosome 12 that has been shown to be linked to IBD by genome screening techniques. It is the cellular receptor for 1,25(OH)2 vitamin D 3 (calcitriol) which has a wide range of different regulatory effects on the immune system. IBD is characterised by activation of the mucosal immune system. AIM: To determine if polymorphisms in the VDR gene are associated with susceptibility to IBD SUBJECTS: European Caucasoids: 158 patients with ulcerative colitis, 245 with Crohn's disease, and 164 cadaveric renal allograft donor controls. METHOD: Single nucleotide polymorphisms (Taq I,Apa I, and Fok I) in VDR were typed in patients with Crohn's disease, ulcerative colitis, and controls by polymerase chain reaction with sequence specific primers. RESULTS: There were significantly more homozygotes for the Taq I polymorphism at codon 352 of exon 8 (genotype “tt”) among patients with Crohn's disease (frequency 0.22) than patients with ulcerative colitis (0.12) or controls (0.12) (odds ratio 1.99; 95% confidence interval 1.14–3.47; p=0.017). CONCLUSION: This study provides preliminary evidence for a genetic association between Crohn's disease susceptibility and a gene that lies within one of the candidate regions determined by linkage analysis.