A molecular pathway controlling cardiomyocyte specification.

描述（由申请人提供）：心脏病是美国的主要死因。心肌功能丧失或无法替代受损心肌，是心血管疾病给我们社会造成巨大负担的基础，平均每39秒就有1人死亡。同样，心血管发育异常是新生儿中最常见的先天性缺陷，占活产婴儿的近1%。许多控制心脏发生的转录因子现在是已知的，并且包括正常心脏生长、形态发生和功能所必需的分子网络。然而，从未定型的早期胚胎中胚层指定心脏祖细胞的初始步骤知之甚少。了解这一过程的进展可以用来开发治疗心血管疾病（包括心力衰竭）的再生策略。我们已经发现了一个遗传途径，这是必要的和足够的胚胎发育过程中产生心肌细胞。该途径的一个中心组成部分是Gata5转录因子，其在心脏发生中的功能相对被忽视。我们发现，在特定的发育窗口期间，Gata5的表达足以有效地从小鼠多能干细胞祖细胞群体产生心肌细胞。我们还发现，在胚胎发生过程中，沿着其姐妹基因gata 6，需要gata 5，正常规格的斑马鱼心肌细胞。因此，我们建立了高通量模型系统来产生或消除心肌细胞的产生。我们开发了工具来发现由gata5在转录和翻译水平上控制的遗传途径。我们开发了新的条件策略来控制空间和时间特异性的途径。我们组建了一个具有全基因组分子网络建模专业知识的团队，我们可以高通量地评估候选网络组件的功能。我们建议在全基因组水平上充分询问促进或限制心肌细胞生成的重要下游分子途径，并发现心肌细胞命运的新调节因子。对这些程序的完整理解将揭示新的细胞或药理学策略，用于恢复由心血管疾病引起的受损心脏组织。为了实现这一目标，提出了以下目标：1）在哺乳动物胚胎干细胞模型中发现足以介导心肌细胞特化的遗传网络。2)使用互补的斑马鱼动物模型鉴定在脊椎动物胚胎中介导心肌细胞特化所必需的调节网络，以及3）在斑马鱼模型中使用条件性功能丧失策略定义心肌细胞特化程序的时间特异性组分。最重要的是，我们将识别和测试心肌细胞特化网络的先前未知组件的功能。

DESCRIPTION (provided by applicant): Heart disease is the major cause of death in the United States. A loss of myocardial function, or failure to replace damaged myocardium, underlies the tremendous burden on our society caused by cardiovascular disease, killing an average of 1 person every 39 seconds. Likewise, cardiovascular developmental anomalies are the most common congenital defects in newborns, presenting in nearly 1% of live births. Many of the transcription factors controlling cardiogenesis are now known and comprise a molecular network essential for normal heart growth, morphogenesis, and function. However, the initial step of specifying cardiac progenitors from uncommitted early embryonic mesoderm is poorly understood. Progress in understanding this process could be exploited to develop regenerative strategies for treating cardiovascular disease, including heart failure. We have discovered a genetic pathway that is both necessary and sufficient during embryonic development for the generation of cardiomyocytes. A central component of this pathway is the Gata5 transcription factor, which has been relatively overlooked with respect to its function in cardiogenesis. We found that expression of Gata5, during a specific developmental window, is sufficient to efficiently generate cardiomyocytes from a mouse pluripotent stem cell progenitor population. We also showed that gata5 is required during embryogenesis, along with its sister gene gata6, for the normal specification of zebrafish cardiomyocytes. Thus, we established high-throughput model systems to generate or eliminate the production of cardiomyocytes. We developed tools to discover the genetic pathways controlled by gata5 at both the transcriptional and translational levels. We developed new conditional strategies to control the pathway with spatial and temporal specificity. We have assembled a team with expertise in genome-wide molecular network modeling, and we can evaluate the function of candidate network components with high throughput. We propose to fully interrogate at the whole genome level the essential downstream molecular pathway(s) that promote or restrict the generation of cardiomyocytes, and to discover novel regulators of cardiomyocyte fate. A complete understanding of these programs will reveal new cellular or pharmacological strategies for restoring damaged cardiac tissue caused by cardiovascular disease. Toward this goal, Aims are proposed to: 1) Discover the genetic network sufficient to mediate cardiomyocyte specification in a mammalian embryonic stem cell model. 2) Identify the regulatory network necessary to mediate cardiomyocyte specification in a vertebrate embryo, using a complementary zebrafish animal model, and 3) Define temporal- specific components of the cardiomyocyte specification program using conditional loss-of-function strategies in the zebrafish model. Most importantly, we will identify and test the function of previously unknown components of the cardiomyocyte specification network.