Elucidation of molecular networks required to limit cardiac cell number

描述(由申请人提供)： 先天性心脏病是非常常见的，大约十分之一的死产和十分之一的活产会发生。在发育过程中，协调各种信号，使器官达到正常功能所需的适当大小。在脊椎动物心脏发育中，已知有几种途径可以促进心脏的诱导和生长，而很少有途径限制心脏的大小。我的长期目标是了解器官如何适当地达到它们的大小。这项拨款的具体目的是阐明在斑马鱼发育过程中限制心脏大小所需的分子途径。在叶伦实验室，我们发现维甲酸(RA)信号是通过独立的细胞机制限制房室细胞的形成所必需的。然而，我们还不清楚限制心肌细胞数量的RA信号的下游效应。在具体目标1中，我将使用镶嵌分析和命运映射来确定哪些细胞必须接受RA信号，以限制心房和心室细胞的数量。在筛选RA信号的下游效应器时，我发现HoxbSb是专门限制心房细胞形成所必需的。在具体目标2中，我将使用镶嵌分析和命运图来描述HoxbSb限制心房细胞数量的细胞机制。我们还不知道有任何基因特定地限制了心室细胞的数量。在具体目标3中，我将使用功能丧失方法来确定特定需要限制心室细胞数量的RA信号的下游效应器。除了RA信号外，可能还有其他信号通路参与限制心肌细胞的形成。在特定的目标4中，我提出了一个突变筛选，以确定限制心肌细胞数量和/或随着RA信号的影响而修改所需的额外基因。从这些实验中收集的信息将使人们更好地了解正常的心脏发育和先天性心脏病的潜在原因。然而，考虑到RA信号作用的许多背景，包括心脏再生、肺分支、干细胞分化和癌症生物学，这些发现很可能也将在人类健康和最终治疗学的发展方面有广泛的应用。

DESCRIPTION (provided by applicant): Congenital heart defects are extremely common, occuring in approximately 1 in 10 still births and 1 in 100 live births. During development, a variety of signals are coordinated that allow an organ to attain its proper size, which is required for its normal function. In vertebrate heart development, several pathways are known to promote induction and growth of the heart, while few pathways are known to restrict the size of the heart. My long-term goal is to understand how organs properly achieve their size. The specific aims of this grant are to elucidate the molecular pathways that are required to restrict the size of the heart during development using zebrafish. In the Yelon lab, we have found that retinoic acid (RA) signaling is required to restrict the formation of both atrial and ventricular cells through independent cellular mechanisms. However, we do not yet understand the downstream effectors of RA signaling involved in limiting the number of cardiac cells. In Specific Aim 1, I will use mosaic analysis and fate mapping to determine which cells must receive RA signaling in order to restrict the numbers of atrial and ventricular cells. In a screen for downstream effectors of RA signaling, I have found that HoxbSb is required to specifically restrict atrial cell formation. In Specific Aim 2, I will use mosaic analysis and fate mapping to characterize the cellular mechanisms through which HoxbSb limits the amount of atrial cells. We do not know any genes involved in specifically restricting ventricular cell number. In Specific Aim 3, I will use loss of function approaches to identify downstream effectors of RA signaling specifically required to limit ventricular cell number. It is likely other signaling pathways besides RA signaling are involved in restricting cardiac cell formation. In Specific Aim 4, I propose a mutagenesis screen to identify additional genes required to restrict the number of cardiac cells and/or modify with the impact of RA signaling. The information gleaned from these experiments will allow a greater understanding of normal heart development and potential causes of congenital heart defects. However, given the many contexts in which RA signaling acts, including cardiac regeneration, lung branching, stem cell differentiation, and cancer biology, it is likely that the findings will also have a broad range of applications toward human health and the eventual development of therapeutics.