Cilia in cardiac morphogenesis

先天性心脏病是最常见的严重出生缺陷，占活产婴儿的0.8%。正常 心脏发育依赖于遗传和表观遗传因素之间复杂的相互作用。特别是， 血流和心功能对心脏形态发生是必不可少的：然而，其机制 这些机械信号被感知和解释仍不清楚。纤毛，这也是必不可少的 心脏LR不对称是通过它们在胚胎组织者(节点)上的功能而发展起来的，最近 被发现在其他管状的、充满液体的器官中起机械传感器的作用，如肾脏。我们已经确定了 小鼠心脏中的一组纤毛，称为心脏纤毛，位于e8.5-e12.5之间，与发育时间相对应。 从血流开始一直延伸到瓣膜形成和间隔。这项提议的目标是 明确心脏纤毛在心脏形态发生中直接作用的机制，不依赖于它们 在LR不对称的产生中所起的作用。纤毛不动但结构正常的小鼠有异常 器官沿左右轴的位置。尽管在7%-50%的受影响小鼠中观察到心脏内缺陷， 相当多的人在心脏结构和功能正常的情况下存活到成年。相比之下，老鼠 完全没有纤毛或纤毛感觉的人有严重的心脏缺陷，其结果是100%外露 在妊娠中期胚胎致死率不依赖于LR轴的发育。这些观察结果表明 纤毛是心脏发育所必需的，与其在LR发育中的功能无关。我们假设 心脏纤毛作为细胞外信号的感受器，如血流、心功能或分泌的配体 影响形态发生。在等级库这项提案的目标1，我们将定义心脏纤毛的作用：它们是 机械传感器、刺猬感受器还是运动结构？为此目的，分布和组成 将检查心脏纤毛。结构性纤毛突变在心脏发育中的作用将是 通过分析突变导致纤毛缺陷的小鼠胚胎的心脏表型进行评估 纤毛生物发生或纤毛机械感觉。心脏缺陷和纤毛分布将是 在突变导致心跳消失的小鼠胚胎中进行评估。纤毛在LR中的作用 发展将与它们的放射内功能区分开来。在等级库目标2，我们将确定 心脏纤毛通过使用Cre-lox技术从心外膜特异性地删除纤毛来发挥其作用， 心内膜、心包和心前区。最后，在规范中。目标3我们将努力定义心脏 纤毛直接形态发生。这里，连接纤毛感觉和心脏的下游信号通路(S) 形态发生将通过分析上皮-间充质转化、增殖和 睫毛功能和生物发生突变的小鼠胚胎心脏中的Hedgehog信号。

Congenital heart disease is the most common serious birth defect, affecting .8% of liveborn infants. Normal cardiac development depends on complex interplay between genetic and epigenetic factors. In particular, blood flow and cardiac function are essential for cardiac morphogenesis: however, the mechanism by which these mechanical signals are sensed and interpreted remains unclear. Cilia, which are also essential in the development of cardiac LR asymmetry via their function at the embryonic organizer (node), have recently been found to function as mechanosensors in other tubular, fluid-filled organs such as the kidney. We have identified a set of cilia, called cardiac cilia, in the mouse heart at e8.5 - e12.5, corresponding to the time in development extending from the onset of blood flow through valve formation and septation. The goal of this proposal is to define the mechanism by which cardiac cilia function directly in cardiac morphogenesis independent of their role in the generation of LR asymmetry. Mice with immotile, but structurally normal cilia have abnormal positioning of organs along the LR axis. Although intracardiac defects are observed in 7-50% of affected mice, a significant number survive to adulthood with structurally and functionally normal hearts. In contrast, mice with complete absence of cilia or ciliary sensing have severe cardiac defects with 100% penetrance that result in mid-gestational embryonic lethality independent of LR axis development. These observations suggest that cilia are required in cardiac development independently from their function in LR development. We hypothesize that cardiac cilia function as sensors for extracellular signlas such as flow, cardiac function or secreted ligands to affect morphogenesis. In Spec. Aim 1 of this proposal, we will define what cardiac cilia do: are they mechanosensors, hedgehog receptors or motile structures? To this end, the distribution and composition of cardiac cilia will be examined. The role of constitutive ciliary mutations on cardiac development will be evaluated by analysis of the cardiac phenotype of mouse embryos with mutations resulting in defective ciliary motility, ciliary biogenesis or ciliary mechanosensation. The cardiac defects and distribution of cilia will be evaluated in mouse embryos with a mutation resulting in an absent heart beat. The role of cilia in LR development will be distinguished from their intracradiac function. In Spec. Aim 2, we will identify where cardiac cilia exert their effect by using Cre-lox technology to delete cilia specifically from the epicardium, endocardium, pericardium and anterior heart field. Finally, in Spec. Aim 3 we will seek to define how cardiac cilia direct morphogenesis. Here, the downstream signaling pathway(s) connecting ciliary sensing with cardiac morphogenesis will be investigated by analyzing epithelial-mesenchymal transformation, proliferation and hedgehog signaling in mouse embryo hearts with mutations in ciliary function and biogenesis.