Cx43 in a Genetic Model of Altered Myocardial Conduction

拟议的研究的目标是确定Cx43在正常心脏传导中的功能作用，并描绘在传导障碍和心律失常的发病机制中的缝隙连接改变耦合的作用。将使用编码主要心脏间隙连接蛋白Cx43的基因的无效等位基因杂合的小鼠（Cx43 +/-小鼠）进行拟定实验。 这些小鼠产生了50%的野生型水平的Cx43，并且在连接心室肌细胞的间隙连接的数量上显著减少。 在成年小鼠中，Cx43表达减少的功能后果是心室传导速度减慢25- 30%。 而Cx43 +/-小鼠的电生理表型在生理条件下是微妙的，在病理生理条件下，可以引起一个更显着的表型。 Cx43 +/-小鼠对急性局部缺血的反应表现为室性心律失常的加速发作和增加的发生率、频率和持续时间。 这项研究的重点是确定耦合减少促进急性和慢性缺血性心脏病心律失常的机制。特定目标1中的研究将阐明间隙连接处电解偶联的速率和程度与急性缺血诱导的室性快速性心律失常发生之间的机制关系。 特定目标2中的研究将定义急性冠状动脉闭塞后Cx43 +/-的心律失常机制，并描述Cx43和改变的细胞间偶联在电触发事件和持续传导异常中的作用，这些事件是急性心肌缺血背景下室性心律失常启动和维持的基础。 在具体目标3中，将通过比较具有愈合的心肌梗死的Cx43 +/-和野生型小鼠的心肌发生来阐明间隙连接重构在慢性缺血性心脏病中心律失常发病机制中的作用。在具体目标4中，将使用在具有定义结构和填充几何形状的图案化阵列中生长的新生小鼠心室肌细胞描绘传导的分子和结构决定因素，并通过高分辨率光学映射进行分析。 拟议的研究结果将确定机制，减少耦合促进急性和慢性缺血性心脏病患者的小鼠模型的室性快速性心律失常。

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.