Gene Interaction Study of Tbx5, Hh pathway and Osr1 in atrial septation

描述(由申请人提供)：先天性心脏病(CHD)在儿童中很常见，每1000名活产儿中约有8例。房间隔缺损(ASD)是冠心病的一种常见形式。本项目的总体目标是研究奇跳相关1(Osr1；Odd1)和Tbx5-Hedgehog(HH)通路之间的分子信号网络在房间隔发育中的作用。Tbx5基因突变会导致人类Holt-Oram综合征(HOS)，其特征是心脏出现房间隔或室间隔缺陷。Hegdehog(HH)-第二心后野(PSHF)中的受体细胞被证明是房间隔祖细胞的池。在初步结果中，我们发现Tbx5在后部的pSHF中是必需的，特别是在HH受体细胞中，才能发生正常的房间隔。这一发现至少部分是由于Tbx5在调节房间隔祖细胞的细胞周期进程中的作用。此外，HH信号在心房祖细胞中的过表达挽救了Tbx5基因敲除胚胎的ASD，这表明从Tbx5向下到HH途径的信号级联。Osr1在心肌背侧系膜的表达与Tbx5和Gli1的表达重叠。重要的是，研究表明，Osr1基因敲除的小鼠胚胎不能形成房间隔。我们进一步证明了Tbx5在房间隔形成中与Osr1直接相互作用。因此，已经发现了Osr1在房间隔形成中的遗传学意义，但Osr1在房间隔形成中的作用机制尚不清楚，这也是本研究的一个重点。我们的中心工作假设是，在房间隔发育过程中，Osr1与Tbx5和HH信号通路相互作用。为了验证这一假设，我们建议揭示Osr1在调控房间隔祖细胞迁移、增殖和存活中的作用。此外，我们将确定在房间隔分离过程中，Osr1与房间隔祖细胞HH信号之间的相互作用。为了解决这个问题，我们将使用遗传镶嵌和免疫组织化学技术来研究形态变化，并将使用分子和遗传学方法来确定特定的房间隔形态在发育过程中形成的机制。这项拟议的研究将为我们理解心脏前体细胞规范中所需的分子网络的长期目标奠定基础。这项有意义的研究将由本科生进行，并有望极大地促进我们对心脏前体细胞规格、房间隔形成的分子基础以及房间隔缺陷的个体发育的理解。

DESCRIPTION (provided by applicant): Congenital heart defects (CHD) are common in children, with an incidence of approximately 8 cases per 1000 live births. Atrial septal defects (ASDs) are a prevalent form of CHD. The overall objective of this project is to investigate the molecular signaling network between the odd-skipped related 1 (Osr1; Odd1) and Tbx5-Hedgehog (Hh) pathway in the development of atrial septum. Mutations in Tbx5 cause Holt-Oram syndrome (HOS) in humans, characterized by atrial or ventricular septal defects in the heart. Hegdehog (Hh)-receiving cells in the posterior second heart field (pSHF) have been shown to define a pool of atrial septal progenitors. In preliminary results, we found that Tbx5 was required in the posterior pSHF, specifically in Hh-receiving cells, in order for normal atrial septation to occur. This finding is at least partially due to the role of Tbx5 in regulating the cel cycle progression of the atrial septal progenitors. Also, overexpression of Hh signaling in atrial progenitors rescues ASDs of Tbx5 knockout embryos, suggesting a signaling cascade from Tbx5 down to Hh- pathway. Expression of Osr1 at the dorsal mesocardium overlaps with expression of Tbx5 and Gli1. Importantly, it has been shown that Osr1 knockout mouse embryos fail to form atrial septum. We further demonstrated that Tbx5 directly interact with Osr1 in atrial septation. Thus, there has been a genetic implication of Osr1 in atrial septation, but th mechanistic role of Osr1 in atrial septation remains unknown and is a focus of the proposed research. Our central working hypothesis is that Osr1 interacts with Tbx5 and Hh signaling pathway in the development of atrial septum. To test this hypothesis, we propose to uncover the roles for Osr1 in regulating the migration, proliferation and survival of atrial septum progenitor cells. Furthermore, we will identify the interaction of Osr1 between Hh signaling in atrial septal progenitors during atrial septation. To approach this problem, we will use genetic mosaic and immunohistochemistry techniques to study morphological alterations, and we will use molecular and genetic approaches to identify the mechanisms by which specific atrial septal morphologies are sculpted during development. This proposed research will lay the groundwork for our long-term goal in understanding the molecular network required in the cardiac progenitor specification. This significant research will be performed by undergraduate students and is expected to substantially advance our understanding on cardiac progenitor cell specification, the molecular basis of atrial septation, and the ontogeny of atrial septal defects.