Myofilament proteins in cardiomyopathy and arrhythmias

项目总结 心肌细胞的收缩装置是心脏功能的中枢。编码基因的突变 肌球蛋白重链和肌球蛋白结合蛋白-C等肌节蛋白导致遗传性 心肌病和心律失常的风险增加。然而，肌节的作用机制 蛋白质突变导致心律失常在很大程度上仍不清楚。我们确定了一种新的成分 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 以及肌球蛋白结合蛋白C。我们发现MyBP-H是由两个不同的基因编码的，MYBPH 指定骨骼肌中的H蛋白，以及产生心脏H蛋白的MYBPHL。此外， 我们发现MYBPHL在心房中高度丰富，并以一种模式在整个脑室中表达 与心室传导系统细胞一致。我们在MYBPHL中发现了一种早停变异 (R255X)在一个患有扩张型心肌病以及房性和室性心律失常的家庭中。删除中的Mybphl 小鼠概括了人类的这一表型，包括房性和室性心律失常和扩张性 心肌病。尽管MYBPHL在左心室低水平表达，但MYBPHL杂合突变 MYBPHL在小鼠和人类中会导致左心功能障碍。这些观察结果表明，MyBP-HL 调节心脏传导系统中的肌丝含量，这是一个研究较少的领域 肌丝的含量和调节。我们假设MyBP-HL调节肌节大小和收缩能力 并与心室传导细胞的功能和形态有关，MyBP-HL导联的丢失 这些细胞的结构变化，进而促进心律失常和左心功能不全。我们 建议通过将Mybphl缺失的小鼠与传导细胞杂交来研究心室传导细胞中的Mybphl 系统报告小鼠，并通过在成人中创建用于删除Mybphl的条件Mybphl空小鼠系 特别是心脏和脑室传导系统。David Barefield博士，这个项目的PI，有一个 具有研究肌丝蛋白和心肌病小鼠模型的强大背景。培训 这项研究的提出将使Barefield博士能够研究心律失常的小鼠模型，以确定其作用 MYBPHL在调节心室传导系统中的作用。这将通过与 研究全动物、全心脏和细胞电生理学的技术。这位候选人正在参加 逐步成为一名独立的学术研究员，在大学或医学院拥有自己的实验室 在美国的研究中心。的特殊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外，还提供了一个出色的环境 实现本提案中规定的目标。

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.