Myofilament proteins in cardiomyopathy and arrhythmias

项目摘要 心肌细胞收缩器是心脏功能的核心。基因突变编码 肌节蛋白质如肌球蛋白重链和肌球蛋白结合蛋白C引起遗传形式的 心肌病和心律失常的风险增加。然而，肌节 导致心律失常的蛋白质突变在很大程度上仍是未知的。我们发现了一种新的成分， 肌丝、肌球蛋白结合蛋白H样（MyBP-HL）。肌球蛋白结合蛋白H最初被发现 沿着肌球蛋白结合蛋白C。我们发现MyBP-H由两个不同的基因编码，MYBPH， 指定骨骼肌中的H蛋白和MYBPHL，MYBPHL产生心脏的H蛋白。此外，委员会认为， 我们发现MYBPHL在心房中高度富集，并以一种模式在整个心室中表达， 与心室传导系统细胞一致我们在MYBPHL中发现了一个提前终止的变异体， （R255 X）在一个家庭与扩张型心肌病和房性和室性心律失常。Mybphl的缺失 小鼠重现了这种人类表型，包括房性和室性心律失常和扩张性心律失常。 心肌病尽管MYBPHL在左心室中表达水平较低，但MYBPHL基因杂合突变在左心室中的表达水平较低。 小鼠和人类中的MYBPHL导致左心室功能障碍。这些观察结果表明，MyBP-HL 调节心脏传导系统中的肌丝含量，这是一个未充分研究的领域， 肌丝含量及调节。我们假设MyBP-HL调节肌节大小和收缩性 并有助于心室传导细胞的功能和形态，MyBP-HL的缺失导致 这些细胞的结构变化反过来又会促进心律失常和左心室功能障碍。我们 我建议通过将Mybphl敲除小鼠与传导细胞交叉来研究Mybphl在心室传导细胞中的作用。 系统报告小鼠，并通过创建条件Mybphl无效小鼠系用于在成年小鼠中缺失Mybphl 心脏和心室传导系统。大卫Barefield博士，这个项目的PI，有一个 在研究肌丝蛋白和心肌病小鼠模型方面有很强的背景。培训 这项研究中提出的方法将使Barefield博士能够研究心律失常的小鼠模型， MYBPHL在调节心室传导系统中的作用。这将通过与专家合作来完成， 研究整个动物、整个心脏和细胞电生理学的技术。这位候选人正在接受 步骤成为一个独立的学术调查员与他自己的实验室在大学或医疗 美国的研究中心。特殊的环境和对这项研究的承诺， 西北大学，除了共同导师的专家团队提供了一个优秀的环境， 实现本提案提出的目标。

PROJECT SUMMARY The cardiomyocyte contractile apparatus is central to heart function. Mutations in the genes encoding sarcomere proteins like myosin heavy chain and myosin binding protein-C cause inherited forms of cardiomyopathy and an increased risk for cardiac arrhythmias. However, the mechanisms by which sarcomere protein mutations lead to arrhythmias remains largely unknown. We identified a novel component of the myofilament, myosin binding protein H-like (MyBP-HL). Myosin binding protein H was originally discovered along with myosin binding protein C. We found that MyBP-H is encoded by two distinct genes, MYBPH which specifies H-protein in skeletal muscle, and MYBPHL, which generates the H-protein of the heart. Moreover, we discovered that MYBPHL is highly enriched in the atria and expressed throughout the ventricle in a pattern consistent with ventricular conduction system cells. We identified a premature stop variant in MYBPHL (R255X) in a family with dilated cardiomyopathy and atrial and ventricular arrhythmias. Deletion of Mybphl in mice recapitulates this human phenotype, including atrial and ventricular arrhythmias and dilated cardiomyopathy. Despite low-level expression of MYBPHL in the left ventricle, heterozygous mutations of MYBPHL in mice and humans leads to left ventricular dysfunction. These observations suggest that MyBP-HL regulates myofilament content in the cardiac conduction system, an understudied area with regard to myofilament content and regulation. We hypothesize that MyBP-HL regulates sarcomere size and contractility and contributes to the function and morphology of ventricular conduction cells, and that loss of MyBP-HL leads to structural changes of these cells which, in turn, promotes arrhythmias and left ventricular dysfunction. We propose to study Mybphl in ventricular conduction cells by crossing the Mybphl null mouse with a conduction system reporter mouse and by creating a conditional Mybphl null mouse line for deletion of Mybphl in the adult heart and in the ventricular conduction system specifically. Dr. David Barefield, the PI of this project, has a strong background studying myofilament proteins and mouse models of cardiomyopathy. The training proposed in this study will allow Dr. Barefield to study mouse models of arrhythmia in order to establish the role of MYBPHL in regulating the ventricular conduction system. This will be done by collaborating with experts in techniques for studying whole-animal, whole-heart, and cellular electrophysiology. The candidate is taking the steps to become an independent academic investigator with his own laboratory at a university or medical research center in the United States. The exceptional environment and commitment to this research at Northwestern University, in addition to the expert team of co-mentors provides an outstanding environment to achieve the goals set out in this proposal.