Objectives: To analyze the IBD5 locus in a homogenous cohort of Ashkenazi Jewish (AJ) children with Crohn disease (CD).
Patients and methods: A total of 83 AJ children with CD and 73 AJ healthy controls were studied. Genotyping for single nucleotide polymorphisms (SNPs) including OCTN1 (SLC22A4; 1672C-->T), OCTN2 (SLC22A5; 207G-->C), IGR2096, IGR2198, and IGR2230 genes was performed using the TaqMan system. NOD2/CARD15 variants also were typed using established methods.
Results: All IBD5 SNPs tested were in linkage disequilibrium (D'>0.8), and showed significant association with CD in our cohort of AJ children. The IGR2096 SNP, which is not located within the same linkage disequilibrium block as the OCTN1 and 2 SNPs, showed an even stronger association with CD (P = 0.017; odds ratio = 1.7). Patients with CD who had the OCTN1 susceptibility allele were more likely to carry 1 of the 3 NOD2/CARD15 SNPs tested (P = 0.01; odds ratio = 4.8).
Conclusions: We have demonstrated a significant association between the IBD5 locus and CD in a homogenous cohort of pediatric AJ patients. Due to the tight linkage disequilibrium in the region, it is not possible to identify the causative IBD5 variant. Future functional studies will ultimately reveal the causative gene variant at this locus.