Genomics and Molecular Medicine Unit, CSIR-Institute of Genomics and Integrative Biology, New Delhi, India.
Academy of Scientific and Innovative Research, CSIR-Institute of Genomics and Integrative Biology Campus, New Delhi, India.
Mol Genet Genomics. 2020 Jul;295(4):1013-1026. doi: 10.1007/s00438-020-01678-6. Epub 2020 May 4.
Obesity, a risk factor for multiple diseases (e.g. diabetes, hypertension, cancers) originates through complex interactions between genes and prevailing environment (food habit and lifestyle) that varies across populations. Indians exhibit a unique obesity phenotype with high abdominal adiposity for a given body weight compared to matched white populations suggesting presence of population-specific genetic and environmental factors influencing obesity. However, Indian population-specific genetic contributors for obesity have not been explored yet. Therefore, to identify potential genetic contributors, we performed a two-staged genome-wide association study (GWAS) for body mass index (BMI), a common measure to evaluate obesity in 5973 Indian adults and the lead findings were further replicated in 1286 Indian adolescents. Our study revealed novel association of variants-rs6913677 in BAI3 gene (p = 1.08 × 10) and rs2078267 in SLC22A11 gene (p = 4.62 × 10) at GWAS significance, and of rs8100011 in ZNF45 gene (p = 1.04 × 10) with near GWAS significance. As genetic loci may dictate the phenotype through modulation of epigenetic processes, we overlapped genetic data of identified signals with their DNA methylation patterns in 236 Indian individuals and performed methylation quantitative trait loci (meth-QTL) analysis. Further, functional roles of discovered variants and underlying genes were speculated using publicly available gene regulatory databases (ENCODE, JASPAR, GeneHancer, GTEx). The identified variants in BAI3 and SLC22A11 genes were found to dictate methylation patterns at unique CpGs harboring critical cis-regulatory elements. Further, BAI3, SLC22A11 and ZNF45 variants were located in repressive chromatin, active enhancer, and active chromatin regions, respectively, in human subcutaneous adipose tissue in ENCODE database. Additionally, these genomic regions represented potential binding sites for key transcription factors implicated in obesity and/or metabolic disorders. Interestingly, GTEx portal identify rs8100011 as a robust cis-expression quantitative trait locus (cis-eQTL) in subcutaneous adipose tissue (p = 1.6 × 10), and ZNF45 gene expression in skeletal muscle of Indian subjects showed an inverse correlation with BMI indicating its possible role in obesity. In conclusion, our study discovered 3 novel population-specific functional genetic variants (rs6913677, rs2078267, rs8100011) in 2 novel (SLC22A11 and ZNF45) and 1 earlier reported gene (BAI3) for BMI in Indians. Our study decodes key genomic loci underlying obesity phenotype in Indians that may serve as prospective drug targets in future.
肥胖是多种疾病的危险因素(如糖尿病、高血压、癌症),它起源于基因与流行环境(饮食习惯和生活方式)之间的复杂相互作用,而这种相互作用在不同人群中是不同的。与匹配的白种人群相比,印度人表现出独特的肥胖表型,即相同体重下腹部脂肪堆积更多,这表明存在影响肥胖的特定于人群的遗传和环境因素。然而,印度人群特有的肥胖遗传因素尚未被探索。因此,为了确定潜在的遗传因素,我们对 5973 名印度成年人的体重指数(BMI)进行了两阶段全基因组关联研究(GWAS),这是一种评估肥胖的常用方法,主要发现结果在 1286 名印度青少年中进一步得到了验证。我们的研究揭示了 BAI3 基因中的 rs6913677 变异(p=1.08×10)和 SLC22A11 基因中的 rs2078267 变异(p=4.62×10)在 GWAS 中有显著意义,ZNF45 基因中的 rs8100011 变异在接近 GWAS 时有显著意义。由于遗传位点可能通过调节表观遗传过程来决定表型,我们将鉴定信号的遗传数据与 236 名印度个体的 DNA 甲基化模式进行了重叠,并进行了甲基化定量性状基因座(meth-QTL)分析。此外,我们使用公开的基因调控数据库(ENCODE、JASPAR、GeneHancer、GTEx)对发现的变异和潜在基因进行了功能推测。在 BAI3 和 SLC22A11 基因中发现的变异可决定独特的 CpG 上的甲基化模式,这些 CpG 含有关键的顺式调控元件。此外,在 ENCODE 数据库中,BAI3、SLC22A11 和 ZNF45 变异分别位于人皮下脂肪组织的抑制性染色质、活性增强子和活性染色质区域。此外,这些基因组区域代表了肥胖和/或代谢紊乱相关关键转录因子的潜在结合位点。有趣的是,GTEx 门户将 rs8100011 鉴定为皮下脂肪组织中稳健的顺式表达数量性状基因座(cis-eQTL)(p=1.6×10),印度受试者的骨骼肌中 ZNF45 基因表达与 BMI 呈负相关,表明其在肥胖中的可能作用。总之,我们的研究在 2 个新基因(SLC22A11 和 ZNF45)和 1 个先前报道的基因(BAI3)中发现了 3 个新的与 BMI 相关的特定于人群的功能遗传变异(rs6913677、rs2078267、rs8100011)。我们的研究揭示了印度人肥胖表型的关键基因组位点,这些位点可能成为未来的潜在药物靶点。