Regulation of Myocardial Regeneration in Zebrafish

心肌梗死（MI），局部缺血引起的心肌局灶性丧失，是这个国家的主要死亡原因。发病率和死亡率与MI密切相关的一个原因是人类心脏通过心肌细胞（CM）（心脏的收缩细胞）的再生来修复自身的能力极其有限。与哺乳动物相比，硬骨鱼对心脏损伤表现出高效的再生反应，能够更新高达20%的切除的心室肌。新的CM在再生过程中是如何产生的还知之甚少。这项建议的目的是利用斑马鱼作为模型，了解心肌再生的细胞和分子机制。以前的研究已经证明了去分化，一个程序性的减少，在一个成熟的，分化的细胞，产生前体细胞在四肢，尾巴，或透镜在低等脊椎动物的再生。据信，这些前体的起源、增殖和模式化由共同的胚胎信号传导途径控制。我们的建议的总体假设是，斑马鱼的心肌损伤激活了调节从收缩性、非增殖性心肌到增殖和图案化的再生CM的转变的分子程序。为了验证这一假设，我们提出了三个具体的目标：1）定义心肌再生过程中的变化，这将包括超微结构分化，基因表达，细胞增殖和心脏功能的详细研究。我们还将比较斑马鱼和小鼠之间损伤诱导的心肌基因表达。2)探讨成纤维细胞生长因子（Fibroblast growth factor，Fgf）信号通路在心肌再生中的作用。我们将研究如何实验增加或减少Fgf信号传导活性影响再生心脏发生，使用新的诱导型转基因株系，促进信号通过Fg受体的调制。3)确定维甲酸（RA）信号在心肌再生中的功能。我们将产生和分析转基因株系，促进显性阴性或组成型！活性RA受体同种型。我们在斑马鱼中的分子遗传学方法将为理解心肌再生过程中的重要调控机制提供基础，并可能导致理解并可能增强人类在MI后显示的有限再生反应的方法。

DESCRIPTION: Myocardial infarction (Ml), the focal loss of cardiac muscle caused by ischemia, is the leading cause of death in this country. One reason why morbidity and mortality are intimately associated with Ml is that the human heart has an extremely limited ability to repair itself through regeneration of cardiomyocytes (CMs), the contractile cells of the heart. By contrast with mammals, the teleost zebrafish displays a highly efficient regenerative response to cardiac injury, able to renew up to 20% of resected ventricular myocardium. How new CMs originate during regeneration is poorly understood. The objective of this proposal is to exploit zebrafish as a model for understanding the cellular and molecular mechanisms of myocardial regeneration. Previous studies have documented how dedifferentiation, a programmed reduction in the specialized, functional components of a mature, differentiated cell, generates precursor cells during regeneration of the limb, tail, or lens in lower vertebrates. It is believed that the origin, proliferation, and patterning of these precursors are controlled by common embryonic signaling pathways. The overall hypothesis of our proposal is that myocardial damage in the zebrafish activates molecular programs that regulate a transition from contractile, non-proliferating cardiac muscle to regenerative CMs that proliferate and are patterned. To test this hypothesis, we propose three specific aims: 1) Define myocardial changes during regeneration This will include detailed studies of ultrastructural differentiation, gene expression, cellular proliferation, and cardiac function. We will also compare injury-induced myocardial gene expression between zebrafish and mice. 2) Determine the functions of Fibroblast growth factor (Fgf) signaling in myocardial regeneration. We will examine how experimental increases or decreases in Fgf signaling activity affect regenerative cardiogenesis, using new inducible transgenic lines that facilitate modulation of signaling through Fg receptors. 3) Identify the functions of retinoic acid (RA) signaling in myocardial regeneration. We wil generate and analyze transgenic lines that facilitate expression of a dominant-negative or constitutive! active RA receptor isotype. Our molecular genetic approach in zebrafish will provide a foundation fo understanding important regulatory mechanisms active during myocardial regeneration, and may lead t approaches for comprehending, and possibly enhancing, the limited regenerative response displayed b humans after Ml.