Genetics and Mechanisms of Mitral Valve Prolapse

 描述（由申请人提供）：二尖瓣脱垂（MVP）影响2.4%的人群，仅在美国每年就有超过7，000例心内直视手术。MVP的特征是瓣叶过度生长，导致脱垂、瓣膜关闭受损和二尖瓣返流（MR），这可能导致严重并发症，包括心内膜炎和充血性心力衰竭。原纤维蛋白-1突变导致马凡氏综合征MVP和细丝蛋白A突变导致X连锁形式的全瓣膜粘液瘤性营养不良，但迄今为止，尽管有明确的遗传成分，没有基因已被确定为非综合征MVP。然而，我们现在有令人信服的，即将发表的数据，从两种方法，显着推进我们的MVP遗传学的理解。首先，我们已经确定Dachsous 1（DCHS 1）突变是MVP的原因。DCHS 1是在果蝇中发现的，在细胞生长和极性中起重要作用。斑马鱼dchs 1基因的敲除导致了房室反流，而这种反流不能被突变的人类蛋白质所挽救。对人DCHS 1的突变体和野生型形式的体外研究揭示了突变体蛋白的半衰期减少。最后，单倍不足的Dchs 1小鼠表现出典型的MVP与改变瓣叶长度和厚度和功能性脱垂。这些结果证实了DCHS 1在二尖瓣疾病中的作用。其次，我们最近完成了一项全基因组关联研究（GWAS），以确定与MVP相关的常见遗传变异。使用2，854例病例的人群，我们确定了6个达到全基因组显著性并在独立队列中复制的新遗传位点。为了鉴定致病基因，我们敲除了斑马鱼三个位点的候选基因，鉴定了两个引起瓣膜表型的基因：Tensin 1（TNS 1），一种整合素和肌动蛋白丝结合蛋白，以及LIM和富含半胱氨酸的结构域1（LMCD 1），它增强了钙调磷酸酶/NFAT信号传导。这些基因是MVP的优秀功能候选者。我们令人兴奋的初步数据为MVP发病机制的研究奠定了基础。我们的假设是，新发现的基因在发育过程中调节细胞迁移，当受到干扰时，导致MVP。具体而言，我们的目标是：1.通过以下方式扩展MVP基因的网络：a.评估剩余的GWAS基因座，B.使用亲和蛋白质组学进行全面的蛋白质相互作用研究，以及c.探讨MVP基因网络在调控细胞迁移中的作用; 2.探讨Tns 1基因敲除小鼠心脏瓣膜功能障碍的发生机制。通过在大型病例对照队列中进行DNA捕获和测序，确定MVP基因突变的负担。二尖瓣脱垂是一个重要的发病率和死亡率的原因。目前没有手术治疗，部分原因是对发病机制知之甚少。鉴于这些挑战，我们相信我们对新发现的MVP基因的研究将有助于更好地了解MVP，并可能最终为预防和治疗这种常见的临床重要疾病提供新的靶点。

 DESCRIPTION (provided by applicant): Mitral valve prolapse (MVP) affects 2.4% of the population and results in more than 7,000 open heart surgeries each year in the US alone. MVP is characterized by excessive valve leaflet growth resulting in prolapse, impaired valve closure and mitral regurgitation (MR), which can cause serious complications including endocarditis and congestive heart failure. Fibrillin-1 mutations cause MVP in Marfan syndrome and Filamin A mutations cause an X-linked form of pan-valvular myxomatous dystrophy, but to date, despite a clear heritable component, no genes have been identified for non-syndromic MVP. However, we now have compelling, soon to be published data from two approaches that significantly advance our understanding of the genetics of MVP. First, we have identified mutations in Dachsous 1 (DCHS1) as a cause of MVP. DCHS1 was discovered in Drosophila and plays an important role in cell growth and polarity. Knockdown of zebrafish dchs1 resulted in atrioventricular regurgitation that could not be rescued by the mutant human protein. In vitro studies of mutant and wild type forms of human DCHS1 revealed reduced half-life of the mutant protein. Finally the haploinsufficient Dchs1 mouse displays classic MVP with altered leaflet length and thickness and functional prolapse. These results confirm a role for DCHS1 in mitral valve disease. Second, we recently completed a genome wide association study (GWAS) to identify common genetic variants associated with MVP. Using a population of 2,854 cases we identified 6 novel genetic loci that reached genome wide significance and replicated in independent cohorts. In order to identify causal genes we knocked down candidate genes from three loci in zebrafish, identifying two genes that cause a valve phenotype: Tensin 1, (TNS1) an integrin and actin filament binding protein, and LIM and cysteine-rich domains 1 (LMCD1), which augments calcineurin/NFAT signaling. These genes are excellent functional candidates for MVP. Our exciting preliminary data set the stage for mechanistic investigation into the pathogenesis of MVP. Our hypothesis is that the newly identified genes regulate cell migration during development which, when perturbed, results in MVP. Specifically, we aim to: 1.Expand the network of MVP genes by: a. evaluating the remaining GWAS loci, b. performing comprehensive protein interaction studies using affinity proteomics, and c. explore the role of the MVP gene network in regulating cellular migration, 2. Investigate the mechanism of valve dysfunction in Tns1 knockout mice, and 3. Determine the burden of mutations in MVP genes by performing DNA capture and sequencing in a large case-control cohort. Mitral valve prolapse is a cause of significant morbidity and mortality. There are currently no treatments short of surgery, in part because the pathogenesis is poorly understood. Given these challenges, we believe that our work on the newly discovered MVP genes will facilitate a greater understanding of MVP and may ultimately provide novel targets for prevention and treatment of this common and clinically important disease.