A Family-based Exome Sequencing Approach to Identify Platelet Aggregation Genes

描述（由申请人提供）：活化血小板在破裂或侵蚀的动脉粥样硬化斑块上聚集，引发动脉系统血栓形成，导致缺血性综合征。血小板在体内聚集的倾向可以通过体外试验来表征，并用于识别具有超聚集血小板的个体，从而有心肌梗死、中风和外周动脉闭塞的风险。这些血小板功能测定具有中等到高度的遗传性，支持了遗传变异是动脉血栓形成倾向的个体差异的假设。在过去的七年中，在nhlbi资助的一项名为GeneSTAR（阿司匹林反应性遗传研究）的研究中，一项全基因组关联研究（GWAS）揭示了非裔美国人和欧洲裔美国人冠心病高风险家庭中多个共同的遗传位点，这些基因通过了严格的GWAS阈值。发现常见的变异决定了低剂量阿司匹林（ASA）干预后天然血小板聚集和残余血小板聚集的变异性。然而，总的来说，通过这种共同变异体方法确定的位点在GeneSTAR家族中占这些表型的总遗传力不到35%。在这项研究中，我们的目标是通过一种综合的方法扩展我们基于家族的GWAS设计，以：1)识别与天然和残留ASA后血小板聚集相关的基因中的罕见变异，测试血小板聚集表型中“缺失遗传性”的很大一部分（即不能由共同的GWAS信号解释）是由于这些罕见变异的假设；2)跟踪GWAS识别的基因座，以确定由GWAS关联信号标记的潜在“因果”变异。在基于家族的外显子组测序方法中，我们将对来自非裔美国人和欧洲裔美国人GeneSTAR家族的200名具有血小板聚集聚集性的高聚集性个体进行测序。这些数据将与nhlbi资助的外显子组测序项目的外显子组变异公共目录相结合，以鉴定与血小板超聚集相关的罕见变异富集的基因。验证的外显子组测序鉴定的基因以及gwas鉴定的位点将依赖于来自其他GeneSTAR家族的1300名非裔美国人和欧裔美国人受试者的靶向深度重测序方法。这种综合GWAS和外显子组方法的结果将使我们更好地理解遗传变异（常见和罕见）在asa后血小板聚集原生和残留的测定中的作用，包括可能的种族差异，并使高危人群冠心病预防治疗的基因型定制成为可能。

DESCRIPTION (provided by applicant): Aggregation of activated platelets on ruptured or eroded atherosclerotic plaques initiates thromboses of the arterial system, resulting in ischemic syndromes. The propensity of platelets to aggregate in vivo can be characterized by in vitro assays and used to identify individuals with hyper-aggregable platelets at risk then for myocardial infarction, stroke, and peripheral arterial occlusions. These platelet function assays are moderately to highly heritable supporting the hypothesis that genetic variations underlie individual variability in the tendency for arterial thrombosis. During the past seven years, in an ongoing NHLBI-funded study called GeneSTAR (Genetic Study of Aspirin Responsiveness), a genome-wide association study (GWAS) revealed multiple common genetic loci that pass stringent GWAS thresholds in African American and European Americans families at high risk for CHD. Common variants were found to determine variability in native platelet aggregation as well as residual platelet aggregation after low dose aspirin (ASA) intervention. However, collectively the loci identified through this common variant approach account for less than 35% the total heritability of these phenotypes in the GeneSTAR families. In this study we aim to extend our family-based GWAS design in an integrative approach to: 1) identify rare variants in genes that are associated with native and residual post- ASA platelet aggregation, testing the hypothesis that a significant fraction of the 'missing heritability' in platelet aggregation phenotypes (i.e. that not explained by the common GWAS signal) is due to these rare variants; and 2) follow up on the GWAS-identified loci to determine the underlying 'causal' variants tagged by the GWAS association signal. In a family-based exome sequencing approach we will sequence 200 hyper-aggregable individuals selected from African American and European American GeneSTAR families with clustering of platelet aggregation. This data will be leveraged against a public catalog of exome variation in the NHLBI-funded Exome Sequencing Project to identify genes enriched for rare variants associated with platelet hyper aggregation. Validated exome sequencing-identified genes along with the GWAS-identified loci will be followed up relying on a targeted deep resequencing approach of 1,300 African American and European American subjects from additional GeneSTAR families. The results from this integrative GWAS and exome approach will lead to a better understanding of the role of genetic variants (common and rare) in the determination of platelet aggregation native and residual post-ASA, including possible racial differences, and should enable genotypic tailoring of preventive therapy for CHD in high-risk individuals. PUBLIC HEALTH RELEVANCE: Native and residual post aspirin platelet hyper aggregation, a strong risk factor for ischemic syndromes, is moderately to highly heritable. Our preliminary data using a genomewide association study (GWAS) in African American and European American families suggest high 'missing heritability' (i.e. that not explained by the common GWAS signal detected). The primary hypothesis is that genes harboring rare genetic variants determining platelet aggregation account for a substantial fraction of missing trait heritability, and an integrative family-based approach of GWAS and exome-sequencing will be applied to test this hypothesis.