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的不到1%。心脏畸形的一个类别，心脏异位，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，异位由转录因子Gli超家族成员Zic 3的突变引起。Gli蛋白是发育过程中hedgehog信号传导的介质，Zic 3是节点处hedgehog信号传导的细胞类型特异性反式激活因子的候选者。本研究的长期目标是确定心脏形态发生所需的L-R模式期间的遗传和分子相互作用。我们已经证明，ZIC 3突变导致体外亚细胞定位异常，ZIC 3缺陷的小鼠重现了患者中鉴定的表型。此外，我们已经证明，Zic 3的行为上游的保守信号转导通路在胚胎节点控制左右图案。除了Zic 3在结周细胞中的已知表达外，我们最近的数据鉴定了在结纤毛中的表达。我们假设Zic 3在结和结周冠细胞中的亚细胞定位对于hedgehog信号转导、左右图案化的确定和随后的心脏成环形态发生是至关重要的。拟议的实验旨在确定组织，细胞类型，和亚细胞的Zic 3的具体作用，并检查Zic 3的表达刺猬信号转导的改变的后果。Aim 1将通过条件性功能丧失方法测试结周冠细胞中Zic 3的细胞自主需求，以实现适当的心脏发育和环状形态发生。目的2将检验Zic 3亚细胞定位的改变改变来自节点的净刺猬信号输出并降低心脏和中线发育缺陷的阈值的假设。了解控制心脏循环的分子层次结构是发展遗传诊断和治疗干预的必要前提。这些研究有可能确定有助于心脏发育的分子和遗传途径，并将开发新的工具来剖析先天性心脏病的潜在机制。

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.