Genetic Regulation of Cardiac Septation

描述(申请人提供)：先天性心脏病(CHD)是最常见的出生缺陷类型，发生在近1%的活产婴儿中。心脏间隔缺陷占冠心病的近50%。大多数CHD的起源是多因素的，但越来越多的证据表明，遗传因素起着重要作用。家族性冠心病罕见病例的识别有助于揭示遗传病因。我们研究的长期目标是了解人类冠心病遗传病因的分子途径。利用全基因组连锁分析，我们发现了GATA4的点突变，它编码对正常心脏发育至关重要的锌指转录因子，与心脏间隔缺陷和其他心脏畸形有关。一个CHD家系中的GATA4 G296S突变揭示了一种新的GATA4和TBX5之间的功能相互作用，这是以CHD为特征的Holt-Oram综合征的遗传原因。与这一体外发现一致，Gata4和Tbx5显示出遗传交互作用，因为Gata4和Tbx5杂合的小鼠具有独特的心脏表型，这是由于心内膜垫发育缺陷造成的。这些发现使我们有了一个切入点来剖析导致CHD的分子通路被破坏。虽然Gata4和Tbx5以及其他转录因子在心脏发育和CHD中发挥核心作用是显而易见的，但对于介导这些发育调节因子作用的靶基因的理解存在重大空白。这是这项提议的重要目标之一。总体假设是GATA4和TBX5调节共同的通路，这些通路对心脏间隔和其他心脏形态发生过程至关重要。本研究的目的是：1.明确Gata4-Tbx5相互作用导致Gata4Tbx5胚胎心脏缺陷的发育过程和细胞谱系(S)。具体目的2.了解Hedgehog信号通路在Gata4Tbx5胚胎心脏表型中的作用。具体目的3.确定Gata4 G296S突变蛋白在胚胎发育中的作用。在Gata4中携带G296S突变的小鼠将被产生，并用于确定该点突变的分子和体内功能缺陷。

DESCRIPTION (provided by applicant): Congenital heart disease (CHD) is the most common type of birth defect occurring in nearly 1% of live births. Cardiac septation defects account for nearly 50% of CHD. The majority of CHD has a multifactorial origin but increasing evidence suggests that genetic factors play a significant role. The identification of rare cases of familial CHD has been instrumental in uncovering genetic etiologies. The long-term goal of our research is to understand the molecular pathways that underlie the genetic etiologies of human CHD. Utilizing genome-wide linkage analysis, we discovered point mutations in GATA4, which encodes a zinc finger transcription factor critical for normal cardiac development, that were associated with cardiac septal defects and other cardiac malformations. A GATA4 G296S mutation in a large pedigree with CHD revealed a novel functional interaction between GATA4 and TBX5, the genetic cause of Holt-Oram syndrome that is characterized by CHD. Consistent with this in vitro finding, Gata4 and Tbx5 displayed a genetic interaction as mice heterozygous for Gata4 and Tbx5 have a unique cardiac phenotype that results from defective endocardial cushion development. These findings allowed us an entry point to dissect the molecular pathways that are disrupted leading to CHD. While it is clear that Gata4 and Tbx5, as well as other transcription factors, play central roles in cardiac development and CHD, there is a major void in the understanding of the target genes that mediate the actions of these developmental regulators. This is one of the important goals of this proposal. The overall hypothesis is that GATA4 and TBX5 regulate common pathways critical for cardiac septation and other cardiac morphogenetic processes. The aims of this proposal are: Specific Aim 1. To determine the developmental processes and cell lineage(s) in which Gata4-Tbx5 interaction is necessary to result in cardiac defects seen in Gata4 Tbx5 embryos. Specific Aim 2. To understand the role of the Hedgehog signaling pathway in the cardiac phenotype of the Gata4 Tbx5 embryos. Specific Aim 3. To determine the role of the Gata4 G296S mutant protein during embryogenesis. Mice that harbor the G296S mutation in Gata4 will be generated and used to define the molecular and functional in vivo deficits of this point mutation.