Genetic Regulation of Cardiac Patterning in Zebrafish

描述（由申请人提供）：器官功能依赖于其每个单独操作部件的适当属性。例如，在脊椎动物胚胎心脏中，循环的有效推进依赖于心房和心室不同的形态、电生理和收缩特性。尽管几个世纪以来人们已经意识到心房和心室心肌细胞之间的关键差异，但将细胞分配到室特异性谱系和直接室特异性分化的基本机制仍然很大程度上是神秘的。我们实验室的研究重点是了解负责腔室命运分配的遗传途径。通过利用斑马鱼作为模式生物，我们发现BMP和FGF信号通路对心房和心室细胞数量有不同的影响，为初步建立心房和心室祖细胞池的机制提供了重要线索。此外，我们的初步数据表明，最初的心室命运决定可能是可塑的，并且存在机制来维持分化心肌的心室特异性特征。总之，我们的研究提出了一个有趣的模型，在这个模型中，心脏场的早期模式，随后是心室身份的后期强化，导致适当的心室命运分配。在这里，我们建议详细评估该模型的各个方面。在Aim 1中，我们将深入研究负责室祖池初始建立的机制。具体来说，我们将使用命运图谱、延时跟踪、马赛克分析和候选效应基因评估来确定BMP信号如何促进心房祖细胞的建立。在目标2中，我们将研究维持腔室身份的机制。我们将利用转基因室性标识报告、延时分析、镶嵌分析和室性特异性调控序列的解剖，测试FGF信号是否通过促进nkx基因的表达来确保室性标识的维持。最后，在Aim 3中，我们将利用我们发现的4种影响心房或心室心肌细胞产生的有趣化合物，寻求确定调节腔室命运分配的新途径。总之，我们的研究将阐明控制腔室命运分配的通路网络的新特征。从长远来看，这项工作有可能揭示心脏先天缺陷的原因，并促进再生医学的创新。

DESCRIPTION (provided by applicant): Organ function relies upon the appropriate attributes of each of its individual operational components. For example, in the embryonic vertebrate heart, effective propulsion of circulation depends upon the distinct morphological, electrophysiological, and contractile traits of the atrial and ventricular chambers. Despite centuries of awareness of the key differences between atrial and ventricular cardiomyocytes, the fundamental mechanisms that allocate cells into chamber-specific lineages and direct chamber-specific differentiation remain largely mysterious. Our laboratory's research focuses on understanding the genetic pathways responsible for chamber fate assignment. By exploiting the utility of the zebrafish as a model organism, we have shown that the BMP and FGF signaling pathways differentially affect atrial and ventricular cell numbers, providing important clues to the mechanisms that initially establish the atrial and ventricular progenitor pools. Furthermore, our preliminary data indicate that initial chamber fate decisions can be plastic and that mechanisms exist to maintain chamber- specific characteristics in differentiated myocardium. Together, our studies suggest an intriguing model in which early patterning of the heart field, followed by later reinforcement of chamber identity, results in proper chamber fate assignment. Here, we propose to evaluate aspects of this model in detail. In Aim 1, we will delve deeper into the mechanisms responsible for the initial establishment of chamber progenitor pools. Specifically, we will use fate mapping, time-lapse tracking, mosaic analysis, and evaluation of candidate effector genes to determine how BMP signaling promotes the establishment of atrial progenitor cells. In Aim 2, we will investigate the mechanisms that maintain chamber identity. Employing transgenic reporters of chamber identity, time-lapse analysis, mosaic analysis, and dissection of chamber-specific regulatory sequences, we will test whether FGF signaling functions to insure maintenance of ventricular chamber identity by promoting expression of nkx genes. Finally, in Aim 3, we will pursue identification of new pathways that regulate chamber fate assignment, taking advantage of our discovery of 4 intriguing compounds that impact atrial or ventricular cardiomyocyte production. Together, our studies will illuminate new features of the network of pathways controlling chamber fate assignment. In the long term, this work has the potential to shed light on the causes of cardiac birth defects and to facilitate innovations in regenerative medicine. PUBLIC HEALTH RELEVANCE: Effective heart function depends upon the specific dimensions and functional characteristics of the atrial and ventricular cardiac chambers. However, the genetic pathways responsible for creating distinct atrial and ventricular tissues are not well understood. In the long term, a better comprehension of this topic will improve our understanding of the causes of common cardiac birth defects and will suggest strategies for directing chamber-specific differentiation of pluripotent cells for therapeutic purposes.