THE ROLE OF SRF IN CARDIAC FUNCTION AND DEVELOPMENT

本申请的总体目标是阐明涉及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的最常见形式，在北美每年每200例肝出生中有1例记录在案。因此，有相当大的兴趣，了解这些疾病的分子和遗传基础。最近在啮齿动物系统中的证据表明，血清反应因子（SRF），MADS（MCMI，Agamous and Deficiens，SRF）盒转录因子家族的成员，是心脏发育和功能的关键调节因子。SRF已被证明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，转基因动物中SRF的心脏特异性过表达导致基因表达的胚胎程序的再诱导，其可导致显著的心脏肥大和近视表型，其模拟在人类充血性心力衰竭的初始发展期间观察到的那些。然而，敲除SRF基因在心脏分化之前是胚胎致死的。因此，尽管SRF在心脏功能和发育中占有中心地位，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，我们提出使用一种强大的新型转基因方法来研究SRF在早期心脏发生过程中的作用，其中将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。然后将分析早期胚胎SRF靶基因表达和心脏形态的结果变化。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.