Role of the Embryonic Node in Cardiac Development and Congenital Heart Disease

描述（由申请人提供）：先天性心脏缺陷是最常见的出生缺陷类型，发生在所有活产婴儿中不到1%。一种类型的心脏缺陷，异位，被认为是由胚胎发育过程中异常的左右模式造成的。在其x连锁形式中，杂性是由转录因子Gli超家族成员Zic3的突变引起的。Gli蛋白是发育过程中hedgehog信号传导的介质，而Zic3是hedgehog信号传导的细胞类型特异性反式激活因子的候选物。本研究的长期目标是确定心脏形态发生所需的L-R模式过程中的遗传和分子相互作用。我们已经证明，ZIC3的突变会导致体外异常的亚细胞定位，并且ZIC3缺陷的小鼠重现了在患者中发现的表型。此外，我们已经证明Zic3作用于一个保守的信号转导途径的上游，在胚胎结处控制左右模式。除了已知的Zic3在结周细胞中的表达外，我们最近有数据确定了在淋巴结纤毛中的表达。我们假设Zic3在淋巴结和结周冠细胞中的亚细胞定位对于hedgehog信号转导、左右模式的确定以及随后的心环形态发生至关重要。本实验旨在确定Zic3的组织、细胞类型和亚细胞特异性作用，并研究Zic3表达改变对hedgehog信号转导的影响。Aim1将通过条件功能丧失的方法测试周结冠细胞对Zic3的细胞自主需求，以实现心脏的正常发育和循环形态发生。Aim 2将验证Zic3亚细胞定位的改变会改变淋巴结的净刺猬信号输出并降低心脏和中线发育缺陷的阈值这一假设。了解控制心脏环的分子层次是发展基因诊断和治疗干预的必要前提。这些研究有可能确定促进心脏发育的分子和遗传途径，并将开发新的工具来解剖先天性心脏病的机制。

DESCRIPTION (provided by applicant): Congenital heart defects are the most common type of birth defect, occurring in just less than 1% of all livebirths. One category of heart defects, heterotaxy, is thought to result from abnormal left-right patterning during embryogenesis. In its X-linked form, heterotaxy results from mutations in Zic3, a member of the Gli superfamily of transcription factors. Gli proteins are mediators of hedgehog signaling during development, and Zic3 is a candidate for a cell type specific trans-activator of hedgehog signaling at the node. The long term goal of this study is to define genetic and molecular interactions during L-R patterning that are required for cardiac morphogenesis. We have shown that mutations in ZIC3 result in abnormal subcellular localization in vitro, and that mice deficient in Zic3 recapitulate the phenotype identified in patients. Further, we have demonstrated that Zic3 acts upstream of a conserved signal transduction pathway acting at the embryonic node to control left-right patterning. In addition to Zic3's known expression in perinodal cells, we have recent data identifying expression in the cilia of the node. We hypothesize that the subcellular localization of Zic3 in the node and perinodal crown cells is critical for transduction of hedgehog signaling, determination of left- right patterning, and subsequent cardiac looping morphogenesis. The proposed experiments are designed to determine the tissue-, cell-type, and subcellular specific roles of Zic3 and examine the consequences of alteration of Zic3 expression on hedgehog signal transduction. Aim1 will test the cell autonomous requirement for Zic3 in perinodal crown cells for proper cardiac development and looping morphogenesis via a conditional loss of function approach. Aim 2 will test the hypothesis that alteration in the subcellular localization of Zic3 changes the net hedgehog signaling output from the node and lowers the threshold for cardiac and midline developmental defects. An understanding of the molecular hierarchy controlling cardiac looping is a necessary prerequisite for the development of genetic diagnostics and therapeutic interventions. These studies have the potential to identify molecular and genetic pathways contributing to cardiac development and will develop novel tools to dissect mechanisms underlying congenital heart disease.