CX43 GAP JUNCTIONS AND NEURAL CREST CELL-CELL SIGNALING

连接蛋白43（Cx43）间隙连接在心脏发育中的重要作用是由Cx43缺陷的基因敲除小鼠在出生时死于心脏缺陷的发现所指示的。然而，Cx43间隙功能在心脏发育中的确切作用仍未得到解决。我们不知道需要它们的特定细胞和组织，或者Cx43缺口功能在这些细胞和组织中的精确功能。基于我们以前的研究和其他实验室的大量工作，我们提出了以下总体假设。假设：Cx43缝隙连接通过调节心脏神经嵴细胞和心肌细胞中的细胞信号在心脏发育中起重要作用。在神经嵴细胞中，Cx43间隙连接介导参与调节神经嵴细胞的迁移和活性的信号传导，从而间接调节心脏发育中的事件。相反，在心肌细胞中，Cx43缝隙连接可能介导参与调节心肌细胞收缩性和心脏传导的细胞信号传导，从而直接影响心脏发育和功能。为了评估这一假设，我们制定了涉及使用转基因小鼠模型和小鼠嵌合体分析的研究。转基因小鼠方法的优势在于它允许以组织特异性方式操纵Cx43功能，并将允许我们检查Cx43间隙连接在神经嵴细胞与肌细胞中的特异性作用。相比之下，嵌合体研究是有利的，因为它们构成了一个独立的和公正的方法来检查心脏发育中的Cx43间隙功能的作用。总之，这些将有助于阐明CVx43间隙连接在心脏发育中的作用，无论是在识别细胞和组织中需要Cx43，以及它在这些细胞和组织中的作用模式。这些研究也可能具有临床意义，因为在实验性Cx43功能干扰中观察到的心脏畸形类似于一类先天性心血管疾病，称为肺动脉闭锁伴室间隔完整。从长远来看，这些研究也将为Cx43间隙连接参与致命性心律失常提供见解。

An essential role for connexin 43 (Cx43) gap junctions in cardiac development is indicated by the finding that knockout mice deficient in Cx43 die at birth from heart defects. However, the precise role(s) of Cx43 gap functions in heart development remains unresolved. We do not known the specific cells and tissues in which they are required, or the precise function served by the Cx43 gap functions in these cells and tissues. Based on our previous studies and a large body of work by other laboratories, we have formulated the following overarching hypothesis. Hypothesis: Cx43 gap junctions play an essential role in heart development by modulating cell signaling in the cardiac neural crest cells and the cardiomyocytes. In Neural crest cells, Cx43 gap junctions mediate signaling involved in regulating the migration and activity of neural crest cells, thereby modulating events in cardiac development indirectly. In contrast, in cardiomyocytes, Cx43 gap junctions may mediate cell signaling involved in regulating myocyte contractility and cardiac conduction, thereby affecting cardiac development and function directly. To evaluate this hypothesis, we have formulated studies involving the use of transgenic mouse models and the analysis of mouse chimeras. The transgenic mouse approach is advantageous in that it allows the manipulation of Cx43 function in a tissue specific manner and will allow us to examine the role of Cx43 gap junctions specifically in neural crest cells vs. the myocytes. In contrast, the chimera studies are advantageous, because they constitute an independent and unbiased method for examining the role of Cx43 gap functions in cardiac development. Together, these will help to elucidate the role of CVx43 gap junctions in cardiac development, both in terms of identifying the cells and tissues in which Cx43 is required, and also its mode of action in these cells and tissues. These studies also are likely to be of clinical significance, as the heart malformations seen with experimental perturbation of Cx43 function resemble a class of congenital cardiovascular disorder referred to as pulmonic atresia with intact ventricular septum. In the long term, these studies will provide insights into the involvement of Cx43 gap junctions in lethal cardiac arrhythmias as well.