Association between vitamin D receptor gene polymorphism and ankylosing spondylitis in Han Chinese

Objectives: To investigate whether vitamin D receptor (VDR) gene polymorphisms confer susceptibility to aankylosing spondylitis (AS) and study its polymorphisms in Han Chinese. Methods: We screened single nucleotide polymorphisms (SNPs) in the VDR region through genome-wide genotyping chips in AS cases and healthy controls, then used the exome sequencing result to analyze all the potential AS-associated SNPs in the VDR gene. Results: Thirty-two SNPs were found in the VDR gene in the genome-wide genotyping chips and the logistic regression result showed no significant difference between AS cases and controls. A total of 46 SNPs in the VDR region were genotyped through exome sequencing, including four functional SNPs (rs731236 [TaqI], rs2228570 [FokI], rs7975232 [ApaI], rs1544410 [BsmI]) and two newly discovered SNPs (12: 48259222 and 12: 48276730). To note, rs731236 and rs2228570 locate in the exons of VDR, which cause synonymous and missense mutation. The association test showed there was no significant difference between AS cases and controls in the allele frequency distribution, but haplotype analysis of rs11168266-rs11168267 show nominal significance (P = 0.01268). Conclusion: Our preliminary study indicates the haplotypes (TG) of rs11168266-rs11168267 in the VDR gene confers susceptibility to AS, which is worth further research.