THE ROLE OF SRF IN CARDIAC FUNCTION AND DEVELOPMENT

本应用程序的总体目标是阐明参与心脏功能和心脏形成的潜在分子机制。先天性心血管异常是人类出生缺陷最常见的形式，在北美每年有记录的每200例肝新生儿中有1例。因此，人们对了解这些疾病的分子和遗传基础非常感兴趣。最近在啮齿动物系统中的证据表明，血清反应因子（SRF）是MADS （MCMI, Agamous and deficiency， SRF）转录因子盒家族的一员，是心脏发育和功能的关键调节因子。SRF已被证明可以调节正常心脏发育和功能所必需的各种心脏和骨骼肌特异性基因，包括心脏和骨骼肌动蛋白、肌营养不良蛋白、肌球蛋白轻链和心房利钠肽基因。与此一致的是，转基因动物的心脏特异性SRF过表达导致基因表达的胚胎程序的重新诱导，可导致戏剧性的心脏肥厚和心肌萎缩表型，类似于在人类充血性心力衰竭的初始发展过程中观察到的现象。然而，在心脏分化之前，SRF基因的敲除是胚胎致死的。因此，尽管SRF在心脏功能和发育中具有中心地位，但SRF在体内心脏形成中的作用尚未得到仔细研究。在当前的应用中，我们建议使用一种强大的新型转基因方法来研究SRF在早期心脏发生中的作用，其中SRF的显性抑制版本的靶向基因插入与胚胎干细胞聚集技术相结合。结果将分析SRF靶基因表达和早期胚胎心脏形态的变化。这些研究将阐明SRF在心脏中的作用机制，并为研究心脏的形成和功能建立强有力的新方法。

The overall objective of this application is to elucidate underlying molecular mechanisms involved in cardiac function and heart formation. Congenital cardiovascular anomalies are the most common form of human birth defect with a recorded instance of 1 per 200 liver births per year in North America. There is therefore considerable interest in understanding the molecular and genetic bases of these diseases. Recent evidence in rodent systems indicates that the serum response factor (SRF), a member of the MADS (MCMI, Agamous and Deficiens, SRF) box family of transcription factors, is a critical regulator of cardiac development and function. SRF has been shown to regulate various cardiac and skeletal muscle specific genes necessary for normal cardiac development and function, including the cardiac and skeletal actin, dystrophin, myosin light chain and atrial natriuretic peptide genes. Consistent with this, cardiac specific over-expression of SRF in transgenic animals results in reinduction of an embryonic program of gene expression that can lead to dramatic cardiac hypertrophic and myopthic phenotypes that mimic those observed during the initial development of congestive heart failure in humans. However, knock-out of the SRF gene is embryonic lethal prior to cardiac differentiation. Therefore, despite a central place for SRF in heart function and development the role of SRF in heart formation in vivo has not been carefully investigated. In the current application we propose to study the role of SRF during early cardiogenesis using a powerful novel transgenic approach in which targeted gene insertion of dominant inhibitory versions of SRF is coupled with embryonic stem cell aggregation techniques. The results changes in SRF target gene expression and cardiac morphology of early stage embryos will then be analyzed. These studies will both elucidate the mechanisms by which SRF functions in heart and will establish powerful new methodologies for studying heart formation and function.