Megf8介导下的TGF-beta超家族信号传导对心内膜垫形成的调控机制研究

Megf8是具有多个EGF或EGF-like结构域的大分子量蛋白。申请人发现Megf8是胚胎左右体轴建立及心脏分隔不可或缺的因子，其突变造成大动脉转位、房室共同通道及内脏异位等畸形。最近则有报道发现MEGF8突变导致以心脏畸形和内脏异位为特征的Carpenter综合征，但目前对Megf8分子功能的理解几乎为空白。基于Megf8小鼠突变体与Acvr2B、Cfc1和Gdf1基因敲除小鼠表型高度相似，我们认为Megf8是TGF-beta超家族信号传导的重要调节因子，进而通过TGF-beta超家族信号调控心内膜垫的生长。预初实验证实Megf8与Acvr2B间存在蛋白相互作用，这进一步支持了我们的假设。本项目计划运用创建的Megf8系列等位基因作为工具，分析Megf8对心内膜垫形成的影响，阐明其调控信号网络，并运用生物化学及细胞生物学技术解析Megf8调控TGF-beta超家族信号传导的分子机制。

Megf8 is a high molecular weight protein with multiple EGF or EGF-like domains. We have found that Megf8 is required for the establishment of Left-right axis and cardiac septation, and that mutation in Megf8 could cause a spectrum of defects including transposition of great artery (TGA), atrioventricular septal defect (AVSD), and heterotaxy. Recently, Megf8 was found to be a cause of Carpenter syndrome featured by cardiac abnormalities and heterotaxy, but the molecular function of this protein is nearly unknown so far. Based on the high degree of phenotypic similarity among Megf8, Acvr2B, Cfc1 and Gdf1 mutants, we hypothesize that Megf8 is a critical component of the TGF-beta superfamily signaling, through which Megf8 is involved in the regulation of endocardial cushion growth. Our preliminary data confirmed a protein-protein interaction between Megf8 and Acvr2B, which further supports our hypothesis. In this project, we propose to analyze the role of Megf8 in endocardial cushion formation, using Megf8 allelic series that we have created. Furthermore, we are planning to dissect the molecular mechanism how Megf8 is involved in the regulation of TGF-beta superfamily signaling pathway through various biochemical and cell biological analysis.