Genetic Regulation of Cardiac Patterning in Zebrafish

描述（由申请人提供）：器官发生从器官祖细胞的适当数量和种类开始。在心脏发育过程中，特定数量和类型的祖细胞的产生是形成适当大小和特征的心腔所必需的。在最简单的形式中，胚胎脊椎动物的心脏由两个主要的腔室组成，一个心室和一个心房。心室和心房心肌细胞在形态学、组织学和生理学上都不同。心室之间的内在差异对有效的心功能至关重要，但负责产生正确数量的心室和心房心肌细胞的机制尚不清楚。我们研究的长期目标是确定调节心肌细胞产生的两个关键方面的遗传途径：适当数量的心脏祖细胞的规范及其在心室和心房群体中的分配。以斑马鱼为模型生物，我们收集了一系列破坏心肌细胞生成的突变。此外，我们已经建立了高分辨率的命运定位技术，能够区分特定基因是否以及如何调节心脏命运分配。这种方法的结合已经产生了一些关于定义和划分心脏祖细胞池的机制的见解。最值得注意的是，我们已经发现了维甲酸（RA）信号的基本早期功能。RA信号的减少通过增加心脏祖细胞数量的命运转化产生过量的心肌细胞。因此，RA在心脏规范中具有强大的抑制作用。在这里，我们建议深入研究RA信号的抑制作用，并研究一种独立的途径，该途径在限制心脏规范方面具有先前未描述的作用。此外，我们将扩大我们的范围，包括信号通路的分析，假设控制心室和心房祖细胞的相对比例。我们的具体目标是：(1)确定RA信号如何限制心脏规范，(2)证明内皮和髓细胞规范通路如何抑制心脏发育潜力，(3)测试Bmp信号在促进心房心肌细胞生成中的作用，以及(4)确定Fgf信号在心室心肌细胞生成中的作用。总之，这些研究将阐明控制心肌细胞产生的通路网络的新特征。从长远来看，这一信息将提高我们对常见心脏出生缺陷原因的理解，并为心脏干细胞的治疗性操作提供策略。

DESCRIPTION (provided by applicant): Organogenesis begins with the specification of the appropriate quantity and variety of organ progenitor cells. During heart development, the generation of specific numbers and types of progenitor cells is necessary for the formation of cardiac chambers of the appropriate size and characteristics. In its simplest form, the embryonic vertebrate heart is composed of two major chambers, a ventricle and an atrium. Ventricular and atrial cardiomyocytes differ morphologically, histologically, and physiologically. The intrinsic differences between chambers are critical for effective cardiac function, but the mechanisms responsible for production of the correct numbers of ventricular and atrial cardiomyocytes are not well understood. The long-term goal of our research is to identify the genetic pathways that regulate two crucial aspects of cardiomyocyte production: the specification of a proper number of cardiac progenitors and their allocation into ventricular and atrial populations. Using the zebrafish as a model organism, we have assembled a collection of mutations that disrupt cardiomyocyte production. Additionally, we have established high- resolution fate mapping techniques capable of distinguishing whether and how specific genes regulate cardiac fate assignment. This combination of approaches has yielded several insights regarding the mechanisms that define and divide the cardiac progenitor pool. Most notably, we have discovered an essential early function of retinoic acid (RA) signaling. Reduction of RA signaling produces an excess of cardiomyocytes, via fate transformations that increase the number of cardiac progenitor cells. Thus, RA has a potent repressive role during cardiac specification. Here, we propose to delve deeper into the repressive influence of RA signaling and to investigate an independent pathway with a previously undescribed role in restricting cardiac specification. Additionally, we will broaden our scope to include the analysis of signaling pathways hypothesized to control the relative proportions of ventricular and atrial progenitors. Our specific aims are: (1) to determine how RA signaling restricts cardiac specification, (2) to demonstrate how endothelial and myeloid specification pathways repress cardiac developmental potential, (3) to test the role of Bmp signaling in promoting atrial cardiomyocyte production, and (4) to identify the roles of Fgf signaling during ventricular cardiomyocyte production. Together, these studies will illuminate new features of the network of pathways controlling cardiomyocyte production. In the long term, this information will improve our understanding of the causes of common cardiac birth defects and suggest strategies for the therapeutic manipulation of cardiac stem cells.