Genetic Studies of Sarcomere-based Cardiac Diseases

描述(由申请人提供)：心肌细胞对机械刺激的感知和反应能力是心脏发生和心肌病的基础。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。这项建议集中在我们对斑马鱼1-肌动蛋白2(Actn2)和TCAP的研究中提出的一种新的抑制性机械转导反应。在心脏生成过程中，肌动蛋白2的耗尽会导致脑室大小严重减小，这可以通过心跳停止来挽救。在分子水平上，我们发现斑马鱼心脏TCAP同源物tcapb在actn2基因敲除胚胎中被激活。Tcapb的耗尽挽救了actn2基因敲除胚胎中缩小的腔体尺寸，表明TCAP的转录激活提供了一种抑制性的机械转导反应。除了心脏发育外，在成年斑马鱼心肌病模型中还检测到激活的TCAP表达，而TCAP的过度表达可以减弱心肌病成年鱼模型中增大的心脏并提高存活率。总之，我们的初步观察支持这一提议的中心假设，即TCAP的转录激活提供了机械刺激引起的抑制性机械转导反应，从而减小了室腔大小。我们将通过以下三个具体目标来检验这一假设。在特定的目标1中，我们建议验证这一假设，即在actn2基因敲除中，室腔大小的减小归因于抑制室腔扩大的机械刺激。在特定的目标2中，我们建议验证TCAP转录激活赋予抑制性机械转导信号以控制室腔大小的假说。在特定的目标3中，我们建议测试TCAP转录激活在各种成人心肌病中发生的假设，并可以增强其对心脏保护的益处。从这里获得的信息将为基于TCAP的心肌病和2G型肌营养不良症的病理生理学提供新的见解。此外，由于心肌细胞中的机械信号在获得性和遗传性心肌病的发病机制中起着关键作用，我们提出的研究将对不同病因的心肌病产生广泛的影响。 公共卫生相关性：这项建议研究机械刺激如何调节脑室大小，这是心脏发生和成人心肌病期间的一个基本问题。我们将努力集中在抑制机械传导反应上，这种反应可以增强，以实现对心肌病的治疗效果。

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. PUBLIC HEALTH RELEVANCE: This proposal studies how mechanical stimuli regulate the ventricle size, a fundamental question during both cardiogenesis and adult cardiomyopathy. We focus our efforts on an inhibitory mechanotransductive response that can be enhanced to achieve therapeutic benefits for cardiomyopathy.