FOXA1先锋转录因子靶基因结合区遗传变异与乳腺癌易感性的关系及机制研究

The molecular mechanisms underlying the transcriptional regulation are especially emphasized in the Encyclopedia of DNA Elements (ENCODE) project. It is of vital importance in understanding the mechanism of transcriptional regulation to explore transcription factor and the corresponding binding sites on genome-wide levels. Genetic variants in FOXA1 pioneer factors binding sites may influence the binding of other transcription factors by modulating the affinity of chromatin for FOXA1, thereby regulate target gene expression levels, and eventually contribute to breast cancer susceptibility. This study will employ the key strategy of post-genome-wide association study, and comprehensively apply bioinformatic approaches to prioritize single nucleotide polymorphisms (SNP) based on their potential functionality on modulating FOXA1 binding affinity. Subsequently, a case-control study with large sample size will be conducted in two dependent populations to identify the breast cancer risk-associated SNPs. The biological mechanisms of the identified risk-associated SNPs will be further assessed by biology functional analyses. This study will make a deep description about the biological effects of transcriptional regulation on the development of breast cancer and advance in our understanding of the causative variants predisposing to breast cancer.

基因的转录调控机制是“DNA元件百科全书”计划描绘的重要内容，深入分析全基因组转录因子及其结合位点对于理解基因的转录调控机制具有特别重要的意义。叉头框蛋白FOXA1先锋转录因子靶基因结合区遗传变异很可能通过改变FOXA1的结合力来影响其他转录因子与靶基因的结合，从而调控靶基因的转录水平，最终导致个体对乳腺癌的遗传易感。本研究紧密结合后GWAS的核心内容，综合应用生物信息学方法在全基因组范畴筛选FOXA1靶基因结合区内影响FOXA1结合力的潜在功能性遗传变异，通过大样本量病例-对照研究，揭示乳腺癌易感相关性遗传变异，最终采用生物学功能实验证实乳腺癌相关遗传变异的功能。本研究不仅深化对FOXA1转录调控机制在乳腺癌易感性中作用的认识，也为识别影响乳腺癌易感性的功能性遗传变异提供了新思路和新方法。所识别的遗传变异可能为乳腺癌风险预测和高危人群筛检等个体化防治提供线索和依据。

本研究整合生物信息学、分子流行病学和分子生物学，较系统地分析了FOXA1靶基因结合区内影响FOXA1结合力的潜在功能性遗传变异在乳腺癌易感性中的作用。首先通过整合各种数据库资源和生物信息学分析，筛选出了4个具有潜在功能的候选遗传变异；随后在两阶段的病例对照研究中发现，与rs6506689 GG基因型携带者相比，TT或TG基因型携带者乳腺癌发病风险显著增加，OR =1.23 (95% CI = 1.07-1.40，P=0.003)。最后通过一系列的功能实验，包括FOXA1敲降前后的报告基因实验，凝胶电泳迁移率实验(Electrophoretic mobility shift assay, EMSA)和表达数量性状位点(expression quantitative trait loci, eQTL)分析，表明FOXA1靶基因结合区遗传变异rs6506689 G>T的T等位基因通过增强与转录因子FOXA1的结合能力而上调RAB31的表达，从而在乳腺癌的发生中起重要作用。本研究系统解析调控型遗传变异通过影响先锋转录因子与DNA的相互作用来调控靶基因的表达，从而在乳腺癌的发生发展中发挥重要作用。