Cellular and Genetic Regulation of Heart Tube Assembly in Zebrafish

描述（由申请人提供）：构建器官是一个复杂的过程，目前还没有得到很好的理解。是什么机制驱使细胞在器官内达到合适的位置和形状？器官内不同类型的细胞在形态发生过程中是如何相互作用的？这些问题可以在心脏的背景下解决，心脏经历了复杂的形态发生，将双侧心肌和心内膜前体细胞重新排列成一个高度特化的多室器官。心脏的形状依赖于早期形态发生时适当的细胞运动，当两种细胞类型组织形成由外层心肌和内心内膜组成的双层心管时。因此，阐明心管形成过程的机制具有重要意义。这对于理解先天性心脏缺陷的原因尤其重要，其中许多先天性心脏缺陷是由于在心脏早期形态发生时未能正确排列心脏细胞造成的。我博士后研究的目标是利用斑马鱼作为模型系统来阐明负责心脏管组装的细胞和遗传调控的关键组成部分。斑马鱼是研究心脏细胞运动的理想系统，因为心脏很容易可视化，适合高分辨率延时成像的转基因的可用性，以及通过功能丧失和功能获得方法操纵基因功能的选择。先前在耶伦实验室的工作已经发现了心肌前体向中线迁移所需的一些基本细胞行为和基因。迁移后，心肌细胞在心内膜周围聚集形成浅锥体，然后延伸形成线状心管。关于驱动心脏管延伸的细胞和分子机制知之甚少。基于我的初步研究，我假设心肌细胞通过中外侧插层来驱动延伸，并且平面细胞极性通路在协调心肌管延伸中起作用。心内膜管延伸的调控可能完全不同，因为内皮管的组装依赖于细胞间接触的精确控制。我的初步数据表明，在心内膜形态发生过程中，细胞作为个体开始定向迁移，随后形成细胞-细胞连接，而VEcadherin在这一过程中起作用。我将通过以下具体目标来验证这些假设：1)确定驱动心肌和心内膜管扩展的细胞行为，2)确定平面细胞极性在心肌管扩展中的作用以及VE-cadherin在心内膜管扩展中的作用，3)进行化学遗传筛选以确定心内膜管扩展的新调控因子。

DESCRIPTION (provided by applicant): Constructing an organ is an elaborate process that is not well understood. What mechanisms drive cells to attain the appropriate position and shape within an organ? How do different cell types within an organ interact during morphogenesis? These questions can be addressed in the context of the heart, which undergoes elaborate morphogenesis to rearrange bilateral populations of myocardial and endocardial precursor cells into a highly specialized multi-chambered organ. Heart shape relies on proper cell movements during early morphogenesis, when both cell types organize to form a two-layered heart tube consisting of an outer myocardium and an inner endocardium. Thus it is of interest to elucidate the mechanisms underlying the process of heart tube formation. This is particularly pertinent to understanding the causes of congenital heart defects, many of which are a result of failure to arrange cardiac cells properly during early heart morphogenesis. The goal of my postdoctoral research is to take advantage of the zebrafish as a model system to elucidate key components of the cellular and genetic regulation responsible for heart tube assembly. The zebrafish is an ideal system in which to study cardiac cell movements due to the easy visualization of the heart, the availability of transgenes appropriate for high-resolution time-lapse imaging, and the options for manipulating gene function through loss- and gain-of-function approaches. Previous work in the Yelon lab has discovered some of the fundamental cellular behaviors and genes required for myocardial precursor migration towards the midline. Following migration, cardiomyocytes coalesce around the endocardium to form a shallow cone, which then extends to form the linear heart tube. Little is known about the cellular and molecular mechanisms driving heart tube extension. Based on my preliminary studies, I hypothesize that myocardial cells undergo mediolateral intercalations to drive extension, and that the planar cell polarity pathway plays a role in orchestrating myocardial tube extension. The regulation of endocardial tube extension may be quite different, as endothelial tube assembly relies on precise control of cell-cell contacts. My preliminary data suggest that, during endocardial morphogenesis, cells begin directional migration as individuals followed by formation of cell-cell junctions, and that VEcadherin plays a role in this process. I will test these hypotheses through the following specific aims: 1) Determining the cell behaviors driving myocardial and endocardial tube extension, 2) Determining the role of planar cell polarity in myocardial tube extension and the role of VE-cadherin in endocardial tube extension, and 3) Conducting a chemical genetic screen to identify new regulators of heart tube extension.