CX43 IN A GENETIC MODEL OF ALTERED MYOCARDIAL CONDUCTION

心肌脉冲传播依赖于细胞间电流传递 在缝隙交界处。心房和心室肌细胞表达不同 多个缝隙连接通道蛋白(连接蛋白)和 由明显不同的缺口空间分布相互连接 交汇点。因此，很可能特定的连接蛋白表型 是不同导电性的重要决定因素 房室肌与细胞间的排列紊乱 偶联作用有助于心律失常的发生。然而，这些假设具有 从来没有直接测试过，也没有具体的功能角色 已知的个体连接蛋白。我们最近发现老鼠 编码Cx43基因的零突变是杂合性的， 主要心脏连接蛋白(Cx43加/减小鼠)，表现出显著的 室性传导减慢，但无房室传导缺陷。 因此，这项资助的重点是Cx43在 Cx43缺陷小鼠，我们所知道的第一个遗传模型 心脏传导异常。我们将检验以下假设：1) Cx43在Cx43正/负和负/负小鼠中的表达缺陷 不会引起心肌组织结构或整体的改变 Cx45和Cx40的组织含量(在特定目标1中进行测试)； Cx43作为主要的细胞间低阻力途径发挥作用 在心室肌(表达Cx43和Cx45)，而不是在心房 肌肉(表达Cx43、Cx45和Cx40)(在特定情况下进行检测 目的2)；3)Cx43缺失和缺失的心肌细胞去偶联 由于Cx43表达减弱而导致的正/负小鼠增强 传导速度的各向异性，支持响应中的慢传导 抑制活性膜性能，增强异质性 反应不应期变化的动作电位时程 (预计会促进心律失常的影响)(将 在特定目标上进行测试3)和4)减少耦合本身 当缺血损伤发生在区域(即，空间上)时导致心律失常 异质性)模式(在特定目标4中进行测试)。为了测试这些 假设，我们将分析Cx43缺陷小鼠 形态计量学、分子和电生理学方法。我们会 测量间隙结电导和单通道特性 直接在房室细胞对中，并表征脉冲 在新生儿Cx43加/加、加/减、 和负性/负性肌细胞的体外多部位、高分辨率 光学测绘和跨膜记录。我们还将描述 缺血诱导的在体心脏传导与心律失常 来自Cx43加/减和加/加小鼠。建议的研究结果 研究将为特定相关人员的角色提供新的见解 基因产物在心脏电生理学中的作用，并将描绘 单个缝隙连接蛋白在心房和心脏中的生物学功能 心室肌细胞。

Myocardial impulse propagation depends on intercellular current transfer at gap junctions. Atrial and ventricular myocytes express different combinations of multiple gap junction channel proteins (connexins) and are interconnected by markedly different spatial distributions of gap junctions. It is likely, therefore, that specific connexin phenotypes are important determinants of the disparate conduction properties of atrial and ventricular muscle and that derangements in intercellular coupling contribute to arrhythmogenesis. However, these hypotheses have never been tested directly nor are the specific functional roles of individual connexins known. We have recently discovered that mice heterozygous for a null mutation in the gene encoding Cx43, the principle cardiac connexin (Cx43 plus/minus mice), exhibit significant slowing of ventricular conduction but no atrial conduction defect. Accordingly, this grant is focused on the functional roles of Cx43 in Cx43 deficient mice, the first genetic model of which we are aware of abnormal cardiac conduction. We will test the hypotheses that: 1) deficient expression of Cx43 in Cx43 plus/minus and minus/minus mice does not cause changes in myocardial tissue structure or in the overall tissue content of Cx45 and Cx40 (to be tested in Specific Aim 1); 2) Cx43 functions as the predominant intercellular low resistance pathway in ventricular muscle (which expresses Cx43 and Cx45) but not in atrial muscle (which expresses Cx43, Cx45 and Cx40) (to be tested in Specific Aim 2); 3) uncoupling of ventricular myocytes in Cx43 minus/minus and plus/minus mice due to diminished Cx43 expression enhances the anisotropy of conduction velocity, sustains slow conduction in response to depression of active membrane properties, and enhances heterogeneity in action potential duration in response to changes in refractoriness (effects which would be expected to promote arrhythmogenesis) (to be tested in Specific Aim 3); and 4) diminishing coupling per se is proarrhythmic when ischemic injury occurs in a regional (i.e., spatially heterogenous) pattern (to be tested in Specific Aim 4). To test these hypotheses, we will analyze Cx43 deficient mice using multiple morphometric, molecular and electrophysiological approaches. We will measure gap junctional conductances and single channel properties directly in atrial and ventricular cell pairs, and characterize impulse propagation in patterned arrays of neonatal Cx43 plus/plus, plus/minus, and minus/minus myocytes in vitro with multisite, high resolution optical mapping and transmembrane recordings. We will also characterize conduction and arrhythmogenesis induced by ischemia in intact hearts from Cx43 plus/minus and plus/plus mice. The results of the proposed research will provide new insights into the roles of a specific relevant gene product in cardiac electrophysiology and will delineate the biological functions served by individual connexins in atrial and ventricular myocytes.