Regulation of cardiac chamber morphogenesis in zebrafish

描述（由申请人提供）：脊椎动物胚胎心脏由两个主要腔室组成，一个心室和一个心房，每个腔室都有其特征形态，确定其功能容量。先天性心脏缺陷常与心腔畸形有关，但对心腔形态发生的调控尚不清楚。心室的形态发生可分为两个主要阶段：心管组装阶段，双侧前体群体联合形成一个管；心室出现阶段，这个简单的圆柱体转变为一系列形态上离散的室。我们研究的长期目标是确定调控这两个阶段的腔室形态发生的细胞和分子机制。利用斑马鱼作为模型生物，我们可以结合胚胎学和遗传学方法，使用高分辨率的实时成像来确定关键基因如何影响心肌细胞的行为。我们对心管组装的初步延时分析表明，这一过程是由多个基因共同驱动的，这些基因共同调节定向心肌细胞运动的区域差异。此外，我们对腔室出现的初步形态计量学分析表明，这一过程是受控制的。由内在和外在因素控制心肌细胞形态的局部变化。最后，我们最近对新突变的研究表明，心脏基因的缓慢融合和变化分别是心脏管组装和腔室出现的关键调节因子。在此基础上，我们建议测试(1)心肌细胞的运动是如何由临界质量的细胞、极化上皮的形成、与内层和心内膜的相互作用以及慢融合功能来调节的；(2)心肌细胞形态是如何由血流动力学、肌节完整性、与心内膜的相互作用以及心功能的变化来调节的。总之，这些研究将揭示心脏发生的基本调控机制，并丰富我们对器官形成的一般范式的理解。

DESCRIPTION (provided by applicant): The embryonic vertebrate heart is composed of 2 major chambers, a ventricle and an atrium, each with a characteristic morphology that defines its functional capacity. Congenital heart defects are often associated with dysmorphic cardiac chambers, but the regulation of cardiac chamber morphogenesis is not well understood. Cardiac chamber morphogenesis can be divided into 2 major phases: heart tube assembly, in which bilateral precursor populations unite to form a tube, and chamber emergence, in which this simple cylinder transforms into a series of morphologically discrete chambers. The long-term goal of our research is to identify the cellular and molecular mechanisms that regulate these 2 phases of chamber morphogenesis. Using the zebrafish as a model organism, we can combine embryologic and genetic approaches, using high-resolution live imaging to determine how key genes influence cardiomyocyte behavior. Our preliminary time-lapse analyses of heart tube assembly suggest that this process is driven by multiple genes that collaborate to regulate regional differences in directed cardiomyocyte movements. Additionally, our initial morphometric analyses of chamber emergence suggest that this process is governed. by both intrinsic and extrinsic factors that control regional changes in cardiomyocyte morphology. Finally, our recent studies of novel mutations suggest that the slow fuse and change of heart genes are critical regulators of heart tube assembly and chamber emergence, respectively. Building on this foundation, we propose to test (1) how cardiomyocyte movements are regulated by a critical mass of cells, formation of polarized epithelia, interactions with endoderm and endocardium, and slow fuse function, and (2) how cardiomyocyte morphology is regulated by hemodynamics, sarcomere integrity, interactions with the endocardium, and change of heart function. Together, these studies will reveal essential regulatory mechanisms of cardiogenesis and also enrich our understanding of general paradigms for organ formation.