Nongmaithem Suraj S, Joglekar Charudatta V, Krishnaveni Ghattu V, Sahariah Sirazul A, Ahmad Meraj, Ramachandran Swetha, Gandhi Meera, Chopra Harsha, Pandit Anand, Potdar Ramesh D, H D Fall Caroline, Yajnik Chittaranjan S, Chandak Giriraj R
Genomic Research on Complex Diseases (GRC Group), CSIR-Centre for Cellular and Molecular Biology, Hyderabad, Telangana 500 007, India.
Diabetes Unit, King Edward Memorial Hospital and Research Centre, Rasta Peth, Pune, Maharashtra 411 011, India.
Hum Mol Genet. 2017 Jul 1;26(13):2551-2564. doi: 10.1093/hmg/ddx071.
Vitamin B12 is an important cofactor in one-carbon metabolism whose dysregulation is associated with various clinical conditions. Indians have a high prevalence of B12 deficiency but little is known about the genetic determinants of circulating B12 concentrations in Indians. We performed a genome-wide association study in 1001 healthy participants in the Pune Maternal Nutrition Study (PMNS), replication studies in 3418 individuals from other Indian cohorts and by meta-analysis identified new variants, rs3760775 (P = 1.2 × 10-23) and rs78060698 (P = 8.3 × 10-17) in FUT6 to be associated with circulating B12 concentrations. Although in-silico analysis replicated both variants in Europeans, differences in the effect allele frequency, effect size and the linkage disequilibrium structure of credible set variants with the reported variants suggest population-specific characteristics in this region. We replicated previously reported variants rs602662, rs601338 in FUT2, rs3760776, rs708686 in FUT6, rs34324219 in TCN1 (all P < 5 × 10-8), rs1131603 in TCN2 (P = 3.4 × 10-5), rs12780845 in CUBN (P = 3.0 × 10-3) and rs2270655 in MMAA (P = 2.0 × 10-3). Circulating B12 concentrations in the PMNS and Parthenon study showed a significant decline with increasing age (P < 0.001), however, the genetic contribution to B12 concentrations remained constant. Luciferase reporter and electrophoretic-mobility shift assay for the FUT6 variant rs78060698 using HepG2 cell line demonstrated strong allele-specific promoter and enhancer activity and differential binding of HNF4α, a key regulator of expression of various fucosyltransferases. Hence, the rs78060698 variant, through regulation of fucosylation may control intestinal host-microbial interaction which could influence B12 concentrations. Our results suggest that in addition to established genetic variants, population-specific variants are important in determining plasma B12 concentrations.
维生素B12是一碳代谢中的一种重要辅助因子，其失调与多种临床病症相关。印度人维生素B12缺乏症的患病率很高，但对于印度人循环中维生素B12浓度的遗传决定因素却知之甚少。我们在浦那孕产妇营养研究（PMNS）的1001名健康参与者中进行了全基因组关联研究，并在来自其他印度队列的3418名个体中进行了重复研究，通过荟萃分析确定了FUT6中的新变异rs3760775（P = 1.2×10-23）和rs78060698（P = 8.3×10-17）与循环中维生素B12浓度相关。尽管在计算机模拟分析中，这两个变异在欧洲人中也得到了重复验证，但效应等位基因频率、效应大小以及可信集变异与已报道变异的连锁不平衡结构的差异表明该区域存在人群特异性特征。我们重复验证了先前报道的FUT2中的变异rs602662、rs601338，FUT6中的rs3760776、rs708686，TCN1中的rs34324219（所有P < 5×10-8），TCN2中的rs1131603（P = 3.4×10-5），CUBN中的rs12780845（P = 3.0×10-3）以及MMAA中的rs2270655（P = 2.0×10-3）。PMNS和帕台农神庙研究中循环维生素B12浓度随年龄增长显著下降（P < 0.001），然而，基因对维生素B12浓度的贡献保持不变。使用HepG2细胞系对FUT6变异rs78060698进行的荧光素酶报告基因和电泳迁移率变动分析表明，该变异具有强大的等位基因特异性启动子和增强子活性，以及各种岩藻糖基转移酶表达的关键调节因子HNF4α的差异结合。因此，rs78060698变异可能通过调节岩藻糖基化来控制肠道宿主 - 微生物相互作用，进而影响维生素B12浓度。我们的结果表明，除了已确定的基因变异外，人群特异性变异在决定血浆维生素B12浓度方面也很重要。
