Mechanistic Role of Rnd3 in Response to Cardiac Stress

描述（由申请人提供）：充血性心力衰竭是世界范围内死亡的主要原因。它仍然是一种无法治愈的疾病，估计晚期疾病患者的两年死亡率为30-50%。虽然我们在心力衰竭的治疗方面取得了很大的进展，但我们对导致心力衰竭的分子机制的理解仍然有限。我的实验室一直致力于研究正常心脏向衰竭转变的分子机制。在这项研究中，我们重点研究了一个小的GTPase Rnd3。Rnd3在心脏中的生物学功能尚不清楚。一项微阵列筛选研究显示，衰竭心肌中Rnd3 mRNA水平显著降低。本研究的目的是探讨Rnd3下调在心力衰竭中的分子机制。在本提案中，我们产生了Rnd3敲除小鼠。我们最近报道了由于Notch信号的过度激活，纯合子小鼠胚胎致死性严重脑积水。Rnd3单倍不足小鼠（Rnd3+/-）在正常生理条件下可生育、可活，无明显异常。然而，在横断主动脉收缩（TAC）后，Rnd3+/-小鼠在压力过载后发生扩张型心肌病（DCM）并心力衰竭。我们的初步数据强烈表明，患者相关Rnd3单倍体不足的小鼠对心脏应激过敏。直接和具有挑战性的问题是Rnd3的下调为什么以及如何导致心力衰竭？转化为心功能障碍的分子机制是什么？为了解决这些问题，我们提出了多种系统的方法，包括体外蛋白质相互作用分析，细胞培养实验和体内遗传动物评估，以及功能丧失和功能获得策略。动物模型包括Rnd3单倍不足小鼠和Rnd3过表达转基因小鼠。这项建议的发现应该会提高临床意义。我们将首次建立遗传因子下调与心脏从正常状态向衰竭状态转变之间的联系，这将为疾病的治疗提供潜在的诊断测试和额外的靶点。该研究对了解人类心力衰竭具有基础和临床转化意义。

DESCRIPTION (provided by applicant): Congestive heart failure is a leading cause of death worldwide. It remains an incurable disease process with an estimated two-year mortality rate of 30-50% for patients with the advanced disease. Although we have made great advances in the treatment for heart failure, our understanding of the molecular mechanism leading to heart failure is still limited. My lab has been committed to study the molecular mechanism involved in the transition of a normal heart to failure. In this study, we focus on the investigation of a smal GTPase Rnd3. The biological function of Rnd3 in the heart remains unexplored. One microarray screening study showed a significant decrease in the Rnd3 mRNA levels in failing human myocardium. The goal of this study is to investigate the molecular mechanisms of Rnd3 downregulation in heart failure. In this proposal, we generated Rnd3 knockout mice. We recently reported that the homozygous mice were embryonically lethal with severe hydrocephalus due to the hyperactivation of Notch signaling. The Rnd3 haploinsufficient mice (Rnd3+/-) are fertile and viable without obvious abnormalities under normal physiological conditions. However, following transverse aortic constriction (TAC), the Rnd3+/- mice developed dilated cardiomyopathy (DCM) with heart failure after the pressure overload. Our preliminary data strongly suggest that the patient-relevant Rnd3 haploinsufficient mice are hypersensitive to cardiac stress. The immediate and challenging questions are why and how does the downregulation of Rnd3 result in heart failure? What is the molecular mechanism involved in the transition to cardiac dysfunction? We propose multiple and systemic approaches including in vitro protein-protein interaction analysis, cell culture experiments, and in vivo genetic animal assessments with loss- and gain-of-function strategies to address these questions. The animal models include Rnd3 haploinsufficient mice as well as Rnd3 overexpression transgenic mice. The findings from this proposal should raise clinical implications. We will, for the first time, establish a connection between the downregulation of a genetic factor and the transition of the heart from a normal to a failing state This will provide a potential diagnostic test and additional target for the treatment of the diseas. The study has basic and clinical translational significance for the understanding of human heart failure.