Cx43 in a Genetic Model of Altered Myocardial Conduction

本研究的目的是确定Cx43在正常心脏传导中的功能作用，并描述间隙连接偶联改变在传导障碍和心律失常发病机制中的作用。拟议的实验将使用编码主要心脏间隙连接蛋白Cx43基因的空等位基因杂合的小鼠（Cx43加/负小鼠）进行。这些小鼠产生野生型Cx43水平的50%，并且连接心室肌细胞的间隙连接数量显著减少。成年小鼠Cx43表达减少的功能后果是心室传导速度减慢25- 30%。在生理条件下，Cx43正/负小鼠的电生理表型是微妙的，而在病理生理条件下，可以引发更显着的表型。在急性局部缺血反应中，Cx43阳性/阴性小鼠室性心律失常发作加速，发生率、频率和持续时间增加。提出的研究重点是确定减少耦合促进急性和慢性缺血性心脏病心律失常的机制。特异性目的1的研究将阐明间隙连接电解偶联的速率和程度与急性缺血引起的室性心动过速发展之间的机制关系。具体目标2的研究将定义急性冠状动脉闭塞后Cx43加/负的心律失常机制，并描述Cx43和细胞间偶联改变在急性心肌缺血时心室心律失常起始和维持的电触发事件和持续传导异常中的作用。在Specific Aim 3中，通过比较Cx43阳性/阴性和野生型心肌梗死愈合小鼠的心律失常，阐明间隙连接重构在慢性缺血性心脏病心律失常发病中的作用。在Specific Aim 4中，传导的分子和结构决定因素将使用在定义结构和包装几何图形阵列中生长的新生小鼠心室肌细胞来描绘，并通过高分辨率光学测绘进行分析。所提出的研究结果将确定在急性和慢性缺血性心脏病小鼠模型中，偶联减少促进室性心动过速的机制。

The goal of the proposed research is to define the functional role of Cx43 in normal cardiac conduction and to delineate the role of altered coupling at gap junctions in the pathogenesis of conduction disturbances and arrhythmias. Proposed experiments will be performed using mice that are heterozygous for a null allele for the gene encoding the major cardiac gap junction protein, Cx43 (Cx43 plus/minus mice). These mice produce 50 percent of the wildtype level of Cx43 and have significant reduction in the number of gap junction interconnecting ventricular myocytes. The functional consequence of reduced Cx43 expression in adult mice is a 25-30 percent slowing of ventricular conduction velocity. Whereas the electrophysiological phenotype in Cx43 plus/minus mice is subtle under physiological conditions, a more dramatic phenotype can be elicited under pathophysiological condition. In response to acute regional ischemia, Cx43 plus/minus mice exhibit accelerated onset and increased incidence, frequency and duration of ventricular arrhythmias. The proposed research is focused on defining mechanisms by which reduced coupling promotes arrhythmias in accute and chronic ischemic heart disease. Studies in Specific Aim 1 will elucidate the mechanistic relationship between the rate and extent of electrical uncoupling at gap junctions and development of ventricular tachyarrhythmias induced by acute ischemia. Studies in Specific Aim 2 will define arrhythmia mechanisms in Cx43 plus/minus following acute coronary occlusion and delineate the roles of Cx43 and altered cell-to- cell coupling in electrical triggering events and sustained conduction abnormalities that underlie initiation and maintenance of ventricular arrhythmias in the setting of acute myocardial ischemia. In Specific Aim 3, the role of gap junction remodeling in the pathogenesis of arrhythmias in chronic ischemic heart disease will be elucidated by comparing arrhythmogenesis in Cx43 plus/minus and wildtype mice with healed myocardial infarcts. And in Specific Aim 4, molecular and structural determinants of conduction will be delineated using neonatal mouse ventricular myocytes grown in patterned arrays of defined structure and packing geometry, and analyzed by high resolution optical mapping. The results of the proposed research will define mechanisms by which reduced coupling promotes ventricular tachyarrhythmias in mouse models of acute and chronic ischemic heart disease in patients.