Unraveling the Genetic Architecture of Very High HDL cholesterol though Transcrip

描述（由申请人提供）：人群研究一致表明高密度脂蛋白胆固醇（HDL-C）和冠心病（CHD）之间存在负相关。虽然遗传变异导致低或缺乏高密度脂蛋白胆固醇已报告与早发冠心病，很少有数据系统地评估高密度脂蛋白胆固醇状态与长寿。这是一个需要解决的重要问题，因为至少50%的HDL-C是遗传介导的。以前，我们的实验室专注于研究极低HDL胆固醇的分子基础（例如，< 20 mg/dL）与早发CHD相关。在此期间，在20个无关家系中的16个中确定了低HDL-C的分子原因，这些家系在3个基因中阐明了功能突变：载脂蛋白A-1（APOA 1），ATP结合盒AI（ABCA 1）和卵磷脂胆固醇酰基转移酶（LCAT）。相反，关于家族性高脂蛋白血症（FHA）的分子基础的信息相当少，FHA是一种以非常高的HDL-C为特征的表型，包括超过100 mg/dL的水平。这是一个及时的研究领域，因为最近的数据表明HDL在减轻炎症和消退动脉粥样硬化病变中的假定作用。为此，我们收集并分析了FHA受试者的血液和DNA样本，这些受试者中存在长寿家族史（至少3名家庭成员活到90岁及以上）。虽然公认全基因组关联研究（GWAS）为在群体水平上评估基因型-表型关联提供了一个出色的渠道，但本提议中要研究的受试者来自生物学上的小家族（n < 10）。此外，已知候选基因的基因组测序，然后进行SNP芯片分析（例如，500 K）未能揭示FHA的分子基础（见下文的初步数据）。最近，大规模平行合成测序（SBS）的使用已经发展成为一种新的和合适的突变发现的方法，因为除了鉴定罕见的和剪接变体，该技术允许测量转录丰度和表达水平的基因的兴趣。此外，SBS将有助于区分SNP和致病突变。基于我们之前在鉴定导致HDL-C缺乏的功能突变方面的成功，并且已经排除了导致FHA的已知候选基因中的突变（见初步数据），我们认为使用SBS的转录组重测序为研究家族成员较少的家系中FHA的分子基础提供了一个很好的平台。因此，R21建议的中心假设是，异常高的HDL-C是单基因突变的结果。我们的总体目标是确定与FHA最极端病例相关的新突变，因为阐明FHA的遗传基础将为研究和促进我们对HDL调节蛋白与动脉粥样硬化血栓形成疾病之间复杂的逆关系的理解提供基础。公共卫生相关性：总的来说，本申请旨在鉴定负责极高水平HDL（“好胆固醇”）的基因。我们从几个不相关的受试者中收集了血液和DNA样本，这些受试者具有与长寿家族史相关的异常高水平的HDL胆固醇（大于120 mg/dL）。人们希望，与长寿相关的高HDL状态有关的新基因的鉴定将促进旨在减少心脏病的新疗法的开发。

DESCRIPTION (provided by applicant): Population studies have consistently demonstrated an inverse association between high-density lipoprotein cholesterol (HDL-C) and coronary heart disease (CHD). While genetic variation causing low or deficient HDL-C has been reported with premature CHD, few data have systematically evaluated high HDL-C states in association with longevity. This is an important issue to resolve because at least 50% of HDL-C is genetically mediated. Previously, our laboratory focused on studying the molecular basis of very low HDL cholesterol (e.g., < 20 mg/dL) in association with premature CHD. During that period, the molecular cause of low HDL-C was identified in 16 of 20 unrelated pedigrees with functional mutations elucidated in 3 genes: apolipoprotein A-1 (APOA1), ATP-binding cassette AI (ABCA1) and lecithin-cholesterol acyltransferase (LCAT). In contrast, considerably less information is available in regard to the molecular basis of familial hyperalphalipoproteinemia (FHA), a phenotype characterized by very high HDL-C, including levels that exceed 100 mg/dL. This is a timely area for investigation in view of recent data demonstrating a putative role for HDL in reducing inflammation and regressing atheromatous lesions. To this end, we collected and analyzed blood and DNA samples from subjects with FHA in whom a familial history of longevity (at least 3 family members living to age 90 years and beyond) exists. While it is recognized that genome wide association studies (GWAS) provide an outstanding conduit for assessing genotype-phenotype associations at the population level, the subjects to be investigated in the present proposal are derived from biologically small families (n < 10). Moreover, genomic sequencing of known candidate genes followed by SNP chip analysis (e.g., 500K) failed to reveal the molecular basis of FHA (see preliminary data, below). Recently, the use of Massively Parallel Sequencing by Synthesis (SBS) has evolved as a new and suitable approach for mutation discovery because in addition to identifying rare and splice-variants, this technology permits measurement of transcript abundance and expression levels of genes of interest. Moreover, SBS will assist in discriminating between SNPs and causative mutations. Based upon our prior success in identifying functional mutations causing HDL-C deficiency and having already ruled out mutations in known candidate genes causing FHA (see preliminary data), we believe that transcriptome resequencing using SBS provides an excellent platform to study the molecular basis of FHA in pedigrees with few family members. Therefore, the central hypothesis of this R21 proposal is that exceptionally high HDL-C is a consequence of single-gene mutations. Our overall aim is to identify novel mutations associated with the most extreme cases of FHA because elucidating the genetic underpinnings of FHA will provide the foundation to investigate and advance our understanding of the complex inverse relationship between HDL regulatory proteins and atherothrombotic disease. PUBLIC HEALTH RELEVANCE: Overall, this application seeks to identify the gene(s) responsible for extremely high levels of HDL, the "good cholesterol". We have collected blood and DNA samples from several unrelated subjects who have extraordinarily high levels of HDL cholesterol (greater than 120 mg/dL) in association with a family history of longevity. It is hoped that the identification of novel genes implicated in high HDL states that are associated with longevity will facilitate the development of novel therapies aimed at reducing heart disease.