Molecular Mechanisms of Cardiac Arrhythmias

描述(申请人提供)：仅在美国，每年就有30多万人死于心律失常。我们实验室正在研究心律失常的发病机制。我们专注于两种心律失常：长QT综合征(LQT)和特发性室颤(IVF)，这两种疾病都会导致年轻的、原本健康的人猝死。在过去的8年里，我们专注于LQT和IVF的遗传学和体外电生理学。我们与其他科学家一起，为LQT和IVF的发病机制确定了一条遗传途径。由于缺乏患者新鲜心脏组织，从组织和器官水平进一步探讨LQT和IVF的发病机制是不可能的。在拟议的研究中，我们计划开发和表征LQT和IVF动物模型，在该模型中，SCN5A(心脏钠通道基因)突变被工程化到小鼠基因组中，以进一步探索心律失常的病因。我们通过靶向SCN5A突变(N1325S)成功地建立了LQT和室性心律失常的小鼠模型。我们的心律失常小鼠的特征导致了工作假说，即早期和之后的去极化(EADS和DADS)是室性心动过速(VT)和室颤(VF)的底物。在拟议的研究中，我们计划继续研究LQT的小鼠模型，以揭示心律失常的详细分子机制，并建立和表征体外受精和获得性LQT的小鼠模型。我们的具体目标是： (1)研究SCN5A的LQT突变在小鼠心脏中的过表达是否会引发电生理重塑；(2)系统地解剖由LQT突变引起的EADS和DADS；(3)系统地检测每类抗心律失常药物的代表性药物对VT/VF的影响，并将结果与EADS/DADS的结果相关联；(4)利用转基因小鼠技术鉴定与体外受精和获得性LQT相关的SCN5A突变。 这项建议中的目标的成功实现将为从根本上理解心律失常的发病机制提供基础。动物模型的评估将有助于确定参与心律失常发生的生理和细胞过程，并弥合体外生物物理缺陷和体内以心律失常易感性为特征的整个动物表型之间的差距。这些研究可能为治疗药物的合理设计提供一个新的框架。

DESCRIPTION (provided by applicant): Cardiac arrhythmias account for more than 300,000 sudden deaths each year in the U.S. alone. Our laboratory is investigating the pathogenesis of cardiac arrhythmias. We focus on two arrhythmic disorders: long-QT syndrome (LQT) and idiopathic ventricular fibrillation (IVF), both of which cause sudden death in the young, otherwise healthy, individuals. During the past 8 years of this project, we focused on genetics and in vitro electrophysiology of LQT and IVF. Together with other scientists, we have defined a genetic pathway for pathogenesis of both LQT and IVF. Further exploration of pathogenic mechanisms of LQT and IVF at the tissue and organ level is impossible because of lack of fresh heart tissues from patients. In the proposed studies we plan to develop and characterize LQT- and IVF-animal models in which SCN5A (the cardiac sodium channel gene) mutations are engineered into the mouse genome to further explore the etiology of arrhythmogenesis. We have successfully established a mouse model for LQT and ventricular arrhythmias by targeting an SCN5A mutation (N1325S). Characterization of our arrhythmic mice has led to the working hypothesis that early and after depolarizations (EADs and DADs) are the substrate for ventricular tachycardia (VT) and ventricular fibrillation (VF). In the proposed studies we plan to continue to study the mouse model for LQT to uncover detailed molecular mechanisms of cardiac arrhythmias, and to generate and characterize mouse models for IVF and acquired LQT. Our specific aims are: (1) To investigate whether over-expression of an LQT-causing mutation of SCN5A in the mouse heart will trigger electrophysiological remodeling; (2) To systematically dissect EADs and DADs induced by a genetic LQT mutation; (3) To systematically determine the effects of representative agents from each class of antiarrhythmic drugs on VT/VF and correlate the findings with results on EADs/DADs; (4) To characterize SCN5A mutations associated with IVF and acquired LQT using the transgenic mouse technology. The successful accomplishment of goals in this proposal will provide a fundamental understanding of the pathogenic mechanisms of cardiac arrhythmias. Evaluation of animal models will help define the physiological and cellular processes involved in arrhythmogenesis, and bridge the gap between the in vitro biophysical defects and the in vivo whole animal phenotype characterized by arrhythmia susceptibility. These studies may provide a new framework for the rational design of therapeutic agents.