Molecular and genetic mechanisms of cardiac conduction development and disease

描述（由申请人提供）：在美国，每年大约有45万人因心室传导紊乱而突然死于心律失常，其中许多死亡与遗传和环境因素有关。然而，对这些遗传因素的识别以及它们如何单独、共同或与环境协同作用来调节导致心律失常事件的细胞和分子行为还远未完成。因此，确定与心律失常有关的新遗传因素的研究可能有助于诊断和治疗易患心律失常的患者。斑马鱼已被证明是理解人类疾病的杰出模型，因为它在形态和生理上与哺乳动物相似，并为生物体提供了一系列基因组工具，促进了大规模的基于表型的筛选。例如，斑马鱼突变体的表型类似于复杂的人类疾病，包括导致心力衰竭和心律失常的常见成人心脏综合征。在一些情况下，人与鱼之间的表型相似性已通过分子定义得到证实。最近，创新转基因工具的创建导致了更复杂的体内细胞和生理分析以及基于表型的筛选。因此，使用基于转基因的体内光学定位系统来执行一种新的基于生理学的正向遗传筛选，我们已经收集了一系列特异性影响心室传导的突变。最值得注意的是，我们发现dococ （dco）和daredevil （ddl）基因是有组织的心室传导的关键调节因子。dco编码Gja3/Cx46，这是一种以前未涉及心脏发育或功能的间隙连接蛋白，而ddl编码RhoGa， RhoG的斑马鱼同源物，可能影响Cx46的运输。与心脏的Cx40、43和45相反，Cx46在心脏发育或功能中的作用仍有待进一步阐明。因此，我们假设Cx46与心脏Cx40、43和45协同作用，通过调节专门心室传导系统心肌细胞之间的细胞间通讯来组织心室传导。我们的具体目标是：1)阐明Cx46调节心室传导的潜在机制；2)确定Cx46心脏功能是否在哺乳动物心脏传导系统中保守；3)探讨rhoga调节心室传导的潜在机制。总的来说，本项目提出的细胞、分子和生理学的结合研究将为人类室性心律失常的机制提供新的和深入的见解。这些研究可能证明对心源性猝死易感患者的预后和诊断以及开发旨在维持和/或改善整体心脏传导的治疗方案是有益的。

DESCRIPTION (provided by applicant): Every year, approximately 450,000 individuals in the United States die suddenly of cardiac arrhythmias due to disorganized ventricular conduction, with many of these deaths linked to both genetic and environmental factors. However, the identification of these genetic factors and how they work alone, together, or in concert with the environment to modulate the cellular and molecular behavior leading to arrhythmic events is far from complete. Thus, studies which identify novel genetic factors linked to cardiac arrhythmias may aid in diagnosis and treatment of patients predisposed for cardiac arrhythmias. The zebrafish has proven to be an outstanding model for understanding human diseases since it has morphologic and physiologic similarities to mammals, and provides an organism with an array of genomic tools which facilitates large-scale phenotype- based screens. For instance, there are zebrafish mutants whose phenotypes resemble complex human disorders, including common adult cardiac syndromes which result in heart failure and arrhythmias. In several cases, phenotypic similarity between man and fish has been confirmed by molecular definition. More recently, the creation of innovative transgenic tools has resulted in more sophisticated in vivo cellular and physiologic analysis as well as phenotypic-based screens. As a result, using a transgenic-based in vivo optical mapping system to perform a new physiologic-based forward genetic screen, we have assembled a collection of mutations that specifically affect ventricular conduction. Most notably, we have discovered that the dococ (dco) and daredevil (ddl) genes are critical regulators of organized ventricular conduction. dco encodes Gja3/Cx46, a gap junction protein not previously implicated in heart development or function, whereas ddl encodes RhoGa, a zebrafish ortholog of RhoG which may affect Cx46 trafficking. In contrast to cardiac Cx40, 43, and 45, the role of Cx46 in heart development or function remains to be further elucidated. Thus, we hypothesize that Cx46 functions in concert with cardiac Cx40, 43, and 45 to organize ventricular conduction through regulation of intercellular communication between specialized ventricular conduction system cardiomyocytes. Our specific aims are: 1) to elucidate underlying mechanisms of how Cx46 regulates ventricular conduction; 2) to determine whether Cx46 cardiac function is conserved in the mammalian cardiac conduction system, and 3) to investigate underlying mechanisms by which rhoga regulates ventricular conduction. Overall, the combination of cellular, molecular and physiologic studies proposed in this project will provide new and in-depth insight into mechanisms of human ventricular arrhythmias. These studies may prove rewarding for prognosis and diagnosis of patients susceptible to sudden cardiac death as well as for developing therapeutic options aimed at maintaining and/or improving overall cardiac conduction. PUBLIC HEALTH RELEVANCE: Every year, approximately 450,000 individuals in the United States die suddenly of cardiac arrhythmias due to disorganized ventricular conduction, with many of these deaths linked to both genetic and environmental factors. Overall, the combination of cellular, molecular and physiologic studies proposed in this project will provide new and in-depth insight into mechanisms of human ventricular arrhythmias. These studies may prove rewarding for prognosis and diagnosis of patients susceptible to sudden cardiac death as well as for developing therapeutic options aimed at maintaining and/or improving overall cardiac conduction.