The Role of Cardiomyopathic Troponin C Mutations in Skeletal and Cardiac Muscle C

项目摘要 心肌肌钙蛋白复合体(CTN)由心肌肌钙蛋白T(CTnT)组成，它与 心肌肌钙蛋白I(CTnI)，参与抑制肌肉收缩 和心肌/慢速骨骼肌钙蛋白C(CTNC)，结合钙离子并触发收缩。总而言之， CTN，调节肌肉收缩，即钙离子敏感性的力量发展，最大力量 发展和基础力量。心肌/慢速骨骼肌钙蛋白C(C/SSTnC)是 在心肌和慢速骨骼肌中表达和存在的CTN。它被认为是 横纹肌的初级钙感受器，已成为肥厚性(HCM)和扩张症的靶标 (DCM)心肌病。HCM或DCM是由TNC突变引起的遗传性疾病 以室壁形态变化和钙离子变化为特征的基因 处理患病的心脏。肌钙蛋白中的HCM突变导致心肌肌丝 对钙离子敏感，导致心律失常和心源性猝死。相比之下， 与扩张型心肌病相关的肌钙蛋白突变使肌丝对钙离子不敏感，这通常会导致充血性 心力衰竭。与心肌病相关的CTN突变在心脏疾病中已被广泛研究 系统。然而，心肌病C/SSTnC突变的功能后果也 在慢速骨骼肌中的存在尚不清楚。这笔赠款要解决的问题是： C/SSTnC突变是否与HCM和DCM有关 骨骼肌缓慢收缩？它们与在心肌中发现的那些相比如何？至 要做到这一点，将利用体外系统以及将用于 测量力/主成分分析的关系。这些测量将在骨骼和 心脏肌肉。在实验室中产生的一种HCM cTNC敲入小鼠的特征是 确定这种突变在完整纤维和脱皮纤维中的体内后果。这样做的目的是 建议解决C/SSTnC突变表型背后的功能差异 心肌和骨骼肌。这些研究将调查缓慢的骨骼肌是否含有 C/SSTnC突变会导致类似于心脏的骨骼异常，以及 在突变敲入小鼠模型中，骨骼肌的功能发生了改变。这些问题是 正在解决的问题是：骨骼系统中发生的变化与变化可比吗 发生在心肌中的？如果慢速骨骼肌的功能变化看起来很小， 在心肌调节中缺失的附加成分有助于挽救 突变？成功地执行这些目标将导致更好地理解心脏与 与TNC基因突变相关的慢性骨骼肌疾病。

Project Summary The cardiac troponin complex (CTn) is made up of cardiac troponin T (CTnT), that attaches the complex to the thin filament; cardiac troponin I (CTnI), involved in the inhibition of muscle contraction and cardiac/slow skeletal troponin C (CTnC), that binds Ca2+ and triggers contraction. Altogether, the CTn, regulates muscle contraction, i.e., Ca2+ sensitivity of force development, maximal force development and basal force. Cardiac/Slow Skeletal Troponin C (C/SSTnC) is the only component of CTn that is expressed and present in both cardiac and slow skeletal muscles. It is considered the primary Ca2+ sensor of striated muscle and has been a target of Hypertrophic (HCM) and Dilated (DCM) Cardiomyopathies. HCM or DCM are genetic disorders caused by the mutations in the TnC gene that are characterized by morphological changes in the ventricular walls and altered Ca2+ handling of the diseased heart. HCM mutations in troponin cause the cardiac myofilament to become sensitized to Ca2+ which is implicated as causing arrhythmias and sudden cardiac death. In contrast, troponin mutations related to DCM desensitize myofilaments to Ca2+ which often leads to congestive heart failure. CTn mutations related to cardiomyopathy have been extensively studied in the cardiac system. However, the functional consequences of cardiomyopathic C/SSTnC mutants also present in slow skeletal muscle are unknown. The question to be addressed in this grant is: What are the functional consequences of C/SSTnC mutations linked to HCM and DCM in the regulation of slow skeletal muscle contraction? How do they compare to those found in cardiac muscle? To accomplish this, in vitro systems will be utilized as well as skinned fibers which will be used to measure the force/pCa relationship. These measurements will be performed in both skeletal and cardiac muscles. An HCM CTnC knock-in mouse generated in the laboratory will be characterized to determine the in vivo consequences of the mutation in intact and skinned fibers. The aims of this proposal address the functional differences that underlie the phenotypes of C/SSTnC mutations in cardiac and skeletal muscles. These studies will investigate whether slow skeletal muscle containing C/SSTnC mutations develops skeletal abnormalities similar to those seen in the heart and whether the function of skeletal muscle is altered in the mutation-knock in mouse model. The questions that are being addressed are: Is the change that occurs in the skeletal system comparable to changes that occur in cardiac muscle? If the functional changes in slow skeletal muscle appear minimal what additional components absent in the regulation of cardiac muscle assist in rescuing the effects of the mutation? Successful execution of these aims will lead to a better understanding of cardiac versus slow skeletal muscle disorders associated with mutations in the TnC gene.