Genetic Studies of Sarcomere-based Cardiac Diseases

描述（由申请人提供）：心肌细胞感知和响应机械刺激的能力在心脏发生和心肌病中都是基本的。然而，我们对机械刺激如何调节心肌细胞大小的理解仍然不完整。这一建议的重点是一种新的抑制性机械转导反应，该反应是由我们对斑马鱼1-肌动蛋白2 （actn2）和tcap （z -盘拉伸传感器复合物的组成部分）的研究提出的。在心脏发生过程中，actn2的消耗导致心室面积严重缩小，这可以通过心跳停止来挽救。在分子水平上，我们发现tcapb，一种斑马鱼心脏tcap同源物，在actn2敲低的胚胎中被激活。在actn2基因敲低的胚胎中，tcapb的缺失可以挽救减少的腔室大小，这表明tcap的转录激活可以产生抑制性机械转导反应。除了心脏发育外，在成年斑马鱼心肌病模型中检测到激活的tcap表达，tcap的过表达减弱了成年斑马鱼心肌病模型中增大的心脏，提高了存活率。总之，我们的初步观察结果支持了该建议的中心假设，即Tcap的转录激活赋予机械刺激引起的抑制机械转导反应，从而减小心室大小。我们将通过以下三个具体目标来检验这一假设。在具体目标1中，我们提出验证actn2敲低导致的室室大小减小归因于抑制室室扩大的机械刺激的假设。在具体目标2中，我们提出验证Tcap的转录激活赋予抑制性机械转导信号以控制心室大小的假设。在Specific Aim 3中，我们提出验证Tcap的转录激活发生在各种成人心肌病中，并且可以增强心脏保护作用的假设。从这里获得的信息将为基于tcap的心肌病和2G型肌营养不良的病理生理学提供新的见解。此外，由于心肌细胞的机械信号在获得性和遗传性心肌病的发病机制中都起着关键作用，因此我们的研究将对不同病因的心肌病产生广泛的影响。

DESCRIPTION (provided by applicant): The ability of cardiomyocytes to sense and respond to mechanical stimuli is fundamental in both cardiogenesis and cardiomyopathies. However, our understanding of how mechanical stimuli modulate cardiomyocyte size still remains incomplete. This proposal focuses on a novel inhibitory mechanotransduction response that has been suggested by our studies of zebrafish 1-actinin2 (actn2), a predominant sarcomeric Z-disc protein, and tcap, a component of the Z-disc-based stretch sensor complex. Depletion of actn2 during cardiogenesis results in severely reduced ventricle chamber size, which can be rescued by arrested heart beat. At the molecular level, we found tcapb, a zebrafish cardiac tcap homologue, is activated in actn2 knockdown embryos. Depletion of tcapb rescues the reduced chamber size in actn2 knockdown embryos, suggesting that transcriptional activation of tcap confers an inhibitory mechanotransduction response. In addition to heart development, activated tcap expression was detected in an adult zebrafish model of cardiomyopathy, and overexpression of tcap attenuates the enlarged heart and increases the survival rate in adult fish models of cardiomyopathy. Together, our preliminary observations support the central hypothesis of this proposal predicting that transcriptional activation of Tcap confers inhibitory mechanotransduction response incurred by mechanical stimuli that reduces ventricular chamber size. We will test this hypothesis by the following three specific aims. In Specific Aim 1, we propose to validate the hypothesis that the reduced ventricular chamber size in actn2 knockdown is ascribed to mechanical stimuli that inhibit ventricular chamber enlargement. In Specific Aim 2, we propose to validate the hypothesis that transcriptional activation of Tcap confers the inhibitory mechanotransduction signaling to control ventricular chamber size. In Specific Aim 3, we propose to test the hypothesis that transcriptional activation of Tcap occurs in various adult cardiomyopathies and can be enhanced for cardioprotective benefits. The information gained from here will provide novel insights into the pathophysiology of Tcap-based cardiomyopathy and muscular dystrophy type 2G. Moreover, because the mechano-signaling in cardiomyocytes plays a pivotal role in the pathogenesis of both acquired and inheritable cardiomyopathies, our proposed research will have broad impacts on cardiomyopathies of different etiologies.