WDR1调控小鼠心脏第二心场发育的作用机制研究

Outflow tract (OFT) malformations account for 30% congenital heart disease in humans, second heart field (SHF) progenitor cells contribute to the development of OFT and right ventricle. However, the process and mechanism of SHF development is still unclear. WDR1 is a major cofactor of the actin depolymerizing factor (ADF)/cofilin in eukaryotes, promoting ADF/cofilin-mediated actin disassembly, and is closely related to cell migration. Previously, our data showed that WDR1 plays important roles in the development of mouse cardiac SHF progenitor cells. Therefore, we proposed: in SHF, WDR1-mediated actin disassembly regulates epithelial polarity and/or cell junction, affects cell migration, thus, regulating the development of OFT and right ventricle. To validate this hypothesis, through SHF progenitor cells-specific-knockout mice model, combining molecular, cellular and developmental approaches, we will clarify the function and regulated mechanisms of WDR1 in the development of SHF at molecule, cell and model animal levels. This study will uncover the developmental process and regulated mechanisms in SHF, and provide experimental basis for the diagnosing, prevention of these diseases.

流出道（OFT）发育畸形约占人类先天性心脏病的30%，OFT和右室由第二心场（SHF）祖细胞发育形成。迄今SHF发育过程及机制仍不清楚。WDR1是肌动蛋白（actin）解聚因子(ADF)/cofilin的主要辅助因子，能促进actin的解聚，并与细胞迁移密切相关。我们前期实验结果显示WDR1在小鼠心脏SHF祖细胞发育中起重要作用，但其作用机制还有待进一步探讨。为此，我们提出假设：WDR1通过actin调控SHF祖细胞的上皮细胞极性和/或细胞连接，影响SHF祖细胞迁移，从而调控OFT和右室的发育。为验证该假说，我们将通过SHF祖细胞特异性敲除Wdr1的小鼠模型，采用分子生物学、细胞生物学和发育生物学的研究方法，在分子、细胞及模式动物层面阐明WDR1在SHF发育中的作用及调控机制。本研究将从WDR1这个新视觉为揭示SHF发育及调控机制奠定基础，为该类疾病的诊断、防治及试管婴儿的筛选提供新思路。

流出道(OFT)异常约占出生时发现的先天性心脏病的30%。第二心脏场（SHF）祖细胞贡献于OFT和右心室（RV）的发育，但其过程在很大程度上仍不清楚。WDR1（WD repeat domain 1）是肌动蛋白解聚因子（ADF）/cofilin的主要辅助因子，能有效地分解ADF/cofilin结合的肌动蛋白丝。它在胚胎心脏发育中的作用尚不清楚。利用Wdr1 floxed小鼠和Nkx2.5-Cre小鼠，我们删除了胚胎期心脏中的Wdr1（Wdr1F/F；Nkx2.5-Cre），发现这些小鼠表现出胚胎致死，以及OFT和RV发育不全的表型。为了研究WDR1在OFT和RV发育中的作用，我们建立了SHF祖细胞特异性Wdr1敲除小鼠（shfKO）。shfKO小鼠在胚胎11.5天（E11.5）开始死亡，E10.5时近端OFT和RV变小。在shfKO胚胎中，SHF细胞贡献于OFT的数量、细胞增殖和细胞数量均未发生变化，而心肌细胞的细胞组织和肌原纤维组装受到严重破坏。在shfKO和Wdr1F/F；Nkx2.5-Cre胚胎的近端OFT和RV中，心肌细胞与外层致密心肌层分离，松散无序地排列成多层心肌层。我们的研究结果表明，WDR1对正常OFT和RV的发育是必不可少的，并提示WDR1介导的肌动蛋白动力学作用可能通过调节心肌细胞的空间排列来控制OFT和RV的大小。