Enrichment of Vitamin D response elements in RA associated loci supports a role for vitamin D in the pathogenesis of RA

The aim of this study was to explore the role of vitamin-D in rheumatoid arthritis (RA) pathogenesis by investigating enrichment of vitamin-D response elements (VDREs) in confirmed RA susceptibility loci and testing variants associated with vitamin-D levels for association with RA. Bioinformatically, VDRE genomic positions were overlaid with non HLA confirmed RA susceptibility regions. The number of VDREs at RA loci was compared to a randomly selected set of genomic loci to calculate an average relative risk (RR). SNPs in the DHCR7/NADSYN1 and CYP2R1 loci, previously associated with circulating vitamin-D levels, were tested in UK RA cases (n = 3870) and controls (n = 8430). Significant enrichment of VDREs was seen at RA loci (p=9.23×10(−8)) when regions were defined either by gene (RR 5.50) or position (RR 5.86). SNPs in the DHCR7/NADSYN1 locus showed evidence of positive association with RA, rs4944076 (p=0.008, OR 1.14 95% CI 1.03-1.24). The significant enrichment of VDREs at RA associated loci and the modest association of variants in loci controlling levels of circulating vitamin-D, supports the hypothesis that vitamin-D plays a role in the development of RA.