Functional consequences of FHC mutations in cardiac MyBPC

描述（由申请人提供）：本提案的长期目标是确定心肌肌球蛋白结合蛋白C （MyBPC）突变导致肥厚性（HCM）和扩张性心肌病（DCM）的机制，这是一种影响全球0.2%人口的疾病，是年轻人猝死的主要原因。MyBPC突变是遗传性心肌病最常见的原因之一，占所有已知病例的40%以上，并与心力衰竭和心脏骤停有关。由于MyBPC是肌动球蛋白相互作用的关键调节剂，因此MyBPC突变引起的初始功能缺陷预计会表现为肌丝水平心肌收缩调节的缺陷。然而，MyBPC突变改变收缩功能并导致疾病的确切分子机制尚不清楚，表达MyBPC的突变是否可以整合到肌节中直接改变收缩功能也尚未确定。缺乏对MyBPC突变如何导致HCM和DCM的基本认识严重限制了我们设计有效治疗方法来克服疾病及其功能后果的能力。拟议的实验将阐明MyBPC突变的功能影响，这些突变已知会导致儿童和成人的一系列疾病严重程度，并将测试MyBPC错义突变与肌节结合并直接改变收缩功能的假设，其主要目的有三个：1)确定MyBPC突变对表达HCM和引起DCM突变的MyBPC重建的心脏纤维中稳态力和动态过桥功能Ca2+依赖性的功能影响。2)通过荧光标记蛋白的稳态和瞬态动力学分析，确定MyBPC突变对atp酶活性、力产生的细丝调节和过桥动力学的影响。3)通过压力容积导管和高分辨率心脏磁共振成像评估急性MyBPC突变基因转移动物的心室结构和功能，确定MyBPC错义突变的体内功能后果。预计这些综合研究的结果将为MyBPC突变导致心功能障碍的潜在机制提供新的见解，并将有助于开发治疗MyBPC相关HCM和DCM的新治疗策略。

DESCRIPTION (provided by applicant): The long-range goal of this proposal is to define the mechanisms by which mutations in cardiac myosin binding protein C (MyBPC) cause hypertrophic (HCM) and dilated cardiomyopathy (DCM), a disease that affects 0.2% of the population worldwide, and is the leading cause of sudden death in young adults. Mutations in MyBPC are among the most common causes of inherited cardiomyopathy accounting for more than 40% of all known cases, and are associated with heart failure and sudden cardiac arrest. Because MyBPC is a critical modulator of actomyosin interactions, the initial functional deficit caused by mutations in MyBPC is expected to manifest as a defect in the regulation of cardiac muscle contraction at the myofilament level. However, the precise molecular mechanisms by which mutations in MyBPC alter contractile function and cause disease are not understood, and it has yet to be established if MyBPC expressing mutations can incorporate into the sarcomere to directly alter contractile function. A lack of fundamental insights into how MyBPC mutations cause HCM and DCM severely limits our ability to devise effective therapies to overcome the disease and its functional consequences. The proposed experiments will elucidate the functional effects of mutations in MyBPC known to cause a range of disease severity in children and adults, and will test the hypothesis that missense mutations in MyBPC incorporate into the sarcomere to directly alter contractile function in three principal aims designed to: 1) Establish the functional effects of MyBPC mutations on the Ca2+-dependencies of steady-state force and dynamic cross-bridge function in cardiac fibers reconstituted with MyBPC expressing HCM and DCM causing mutations, 2) Define the effects of MyBPC mutations on ATPase activity, thin filament regulation of force generation, and cross-bridge kinetics, using steady-state and transient kinetic analysis of fluorescently labeled proteins, and 3) Determine the in vivo functional consequences of missense mutations in MyBPC by assessing ventricular structure and function using pressure-volume catheterization and high resolution cardiac magnetic resonance imaging in animals subjected to acute gene transfer of mutant MyBPC. It is expected that results from these integrative studies will provide novel insights of the underlying mechanisms by which mutations in MyBPC cause cardiac dysfunction and will aid in the development of novel therapeutic strategies for treatment MyBPC related HCM and DCM.