染色体7q36.3区域遗传变异与成人肥胖表型的关联研究

According to published studies, about 40-70% of the individual variation in obesity can be attributable to genetic factors suggesting the importance in the search for obesity susceptibility loci aimed at elucidating the molecular mechanisms in obesity. Supported by the 2008 National Natural Science Foundation, our genome-wide linkage scan for BMI identified chromosome 7q36.3 as the region showing the highest linkage, a discovery strongly supported by linkage result from a large European consortium. Encouraged by our result, this project aims at performing an association-based fine mapping of genes in the 7q36.3 region that are potentially susceptible to obesity phenotype. The discovery stage will include 1500 participants from Qingdao Diabetes Prevention Project Cohort. Genotyping of selected tagSNPs will be done using customized gene chips. Data analysis will be done on single SNPs, haplotypes as well as functional genes in the 7q36.6 region by using bioinformatics tools such as Plink, i-Gsea4Gwas. Statistically significant SNPs found in the discovery stage will be selected for further confirmation in the replication stage with 3000 individuals from above mentioned cohort. Sequenom MassARRAY system will be used for genotyping in replication stage. Gene by environment interactions will also be included in the analysis together with the main effects by genetic and environmental factors in both stages. The study is expected to deepen our understanding of obesity etiology and to help with development of more efficient prevention and treatment strategies.

研究表明，肥胖的遗传度为0.4～0.7，找寻肥胖的易感基因对揭示其生物学机制有着重要意义。课题组2008年国家自然科学基金的研究结果显示，体质指数(BMI)与染色体7q36.3区域高度连锁。因此，课题组拟从《青岛糖尿病预防》队列中选择研究对象，继续开展关联研究。本研究分为两个阶段：发现阶段，选取1500人，用定制基因芯片对7q36.3染色体区域内所选tagSNPs进行分型，利用Plink、I-Gsea4Gwas等软件探索与体质指数、腰臀比、体脂率等肥胖表型相关的SNP、单体型、功能基因，及其与环境因素的交互作用。验证阶段，在同一队列中另选取 3000人，采用MassArray时间飞行质谱系统对发现阶段有统计学意义的SNP进行基因分型，验证染色体7q36.3区域遗传变异及其与环境因素的交互作用对肥胖表型的影响。研究结果可为肥胖的病因、预防干预以及治疗等研究提供新的依据。

前次国家自然科学基金项目发现体质指数（BMI）与染色体7q36.3和8q21.13区域高度连锁。本次采用两阶段病例对照设计，开展中国北方汉族人群的肥胖易感基因关联研究。发现阶段，从《青岛市糖尿病队列》中选择肥胖者16名（BMI≥30 kg/m2），利用目标捕获联合第二代测序技术，对其7q36.3和8q21.13染色体区域开展测序，共读出16个样本的12,131个遗传变异，以千人基因组计划中504名东亚人为对照，确切概率法经多重校正计算q值，发现65个有统计学意义的差异SNP，位于25个邻近基因上（INSIG1, FABP5, PTPRN2, VIPR2, WDR60, SHH, UBE3C, LMBR1, PAG1, IMPA1, CHMP4, SNX16, BLACE, EN2, CNPY1, LOC100506302, RBM33, LOC389602, LOC285889, LINC01006, NOM1, DNAJB6, LOC101927914, ESYT2, LINC00689），使用Haploview 4.2对位于相近染色体区域的有意义SNPs开展连锁不平衡单体型分析发现10对强连锁不平衡位点。将有意义差异基因列表提交至网站，开展基因富集分析，发现了2个主要的相关基因集(LIPID_RAFT, LIPID_METABOLIC_PROCESS）。验证阶段，从同一队列中，按年龄、性别匹配的原则，另选取肥胖与正常对照384对，采用Sequenom时间飞行质谱系统对发现阶段有统计学意义的56个SNP进行基因分型，并比较，结果显示两组间rs6988941、rs1182422、rs2788478基因型差别有统计学意义。本研究为进一步验证肥胖易感基因提供了理论依据。