ABSTRACT
The first gene associated with Crohn disease (CD) has been identified as CARD15 (16q12). Three variants, R702W, G908R and 1007fsinsC are strongly and independently associated with the disease. A second gene, conveying a smaller risk for inflammatory bowel disease (IBD), has been identified as DLG5 (10q23). We assess the frequency of the CARD15 SNPs and of the R30Q mutation in DLG5 and their contribution to the development of CD in a cohort of unrelated IBD patients (151 CD, 325 ulcerative colitis (UC)) and healthy controls (236) from South-east Norway (IBSEN cohort). Genotype-based tests of population differentiation using 23 SNPs across CARD15, together with estimates of F(ST), indicated that the German and Norwegian background populations could be differentiated at the CARD15 locus. The Norwegian and German CD samples exhibited particularly strong differentiation at the three predisposing loci and those marking their background haplotype. There were significantly lower frequencies of the CARD15 SNPs and no significant association with CD in the Norwegian samples. Only a marginal association was observed for the subphenotypes ileitis and ileocolitis vs colitis (P=0.048). The population attributable risk percentage (PAR%) for CARD15 variants in the Norwegian cohort is the lowest reported for a European population (1.88%), except Iceland. Similarly, the DLG5 variant showed no association with CD or IBD, however, there was a negative correlation with stricture (P=0.035). The present results are consistent with an emerging pattern of a low frequency of the CARD15 variants in Northern countries where the prevalence of IBD is greatest.
Subject(s)
Crohn Disease/genetics , Genetic Heterogeneity , Membrane Proteins/genetics , Nod2 Signaling Adaptor Protein/genetics , Tumor Suppressor Proteins/genetics , Adult , Case-Control Studies , Female , Genetic Predisposition to Disease , Germany , Humans , Male , Mutation , Norway , Polymorphism, Single Nucleotide/geneticsABSTRACT
BACKGROUND: Crohn's disease is a heterogeneous disorder for which NOD2 (CARD 15) has been identified as a susceptibility gene. We investigate the relation between NOD2 genotype and phenotypic characteristics of patients with Crohn's disease. METHODS: Hypotheses about the relation between NOD2 genotype and Crohn's disease phenotype were generated retrospectively from a group of 446 German patients with this disorder. Positive findings (p<0.10) were verified in prospectively established cohorts of 106 German and 55 Norwegian patients with Crohn's disease. All patients were genotyped for the main coding mutations in NOD2, denoted SNP8, SNP12, and SNP13, with Taqman technology. FINDINGS: In the retrospective cohort, six clinical characteristics showed noteworthy haplotype association: fistulising, ileal, left colonic and right colonic disease, stenosis, and resection. In the German prospective cohort, these haplotype associations could be replicated for ileal (p=0.006) and right colonic disease (p < or =0.001). A similar trend was noted in the Norwegian patients. INTERPRETATION: We recorded a distinct relation between NOD2 genotype and phenotype of Crohn's disease. Test strategies with NOD2 variations to predict the clinical course of Crohn's disease could lead to the development of new therapeutic paradigms.