EIF4A3通过抑制Wnt/β-catenin信号通路调控胚胎早期发育的作用及机制研究

Eukaryotic translation initiation factor 4A (EIF4A) includes three members 1, 2, and 3 which are all core components of exon-junction complex. EIF4As participate in pre-mRNA spicing events, such as mRNA translation, nonsense-mediated mRNA decay, and mRNA localization. EIF4A3 shuttled between cytoplasm and nucleus. The Wnt/β-catenin signaling pathway plays an important role during embryogenesis in vertebrates. However, whether or not EIF4A regulates Wnt signaling is still poorly understood. We identified Eif4a3 negatively modulated Wnt/β-catenin signals. The preliminary results showed that EIF4A3 and the Wnt /β-catenin signals transcription factor TCF/LEF are physically interacted. To explore the biological functions of Eif4a3, overexpression, gene knockout, and whole amount in situ hybridization as well as cultured cells will be used to investigate the underlying molecular mechanism of Eif4a3 in Wnt/β-catenin signals. The completion of the proposed studies will provide novel insights into the relationship between EIF4A and Wnt/β-catenin signaling. The anticipated results will lead to understand how EIF4A modulates early embryonic development in zebrafish and by which mechanism EIF4A regulates Wnt/β-catenin signals. Misregulation of Wnt/β-catenin signaling causes disease, most prominently cancer, a better understanding of the biology of Wnt/β-catenin signals regulated by EIF4A will likely help to understand the role of EIF4A in disease and cancer.

真核翻译起始因子4A3 (EIF4A3)是外显子连接复合体(EJC)的核心组分参与多种前体mRNA剪接事件。本项目前期发现模型动物斑马鱼Eif4a3抑制Wnt/β-catenin信号通路，并与介导该通路的转录因子TCF/LEF位于同一蛋白复合体。采用TALEN基因编辑技术敲除该基因后斑马鱼突变体胚胎体轴形成发生缺陷。本研究拟从Eif4a3负调控Wnt/β-catenin通路切入，利用基因斑马鱼敲除突变体，结合体内胚胎及体外细胞系分析，详细揭示Eif4a3的生理功能，并解析其作用的分子机制，进而阐明Eif4a3和Wnt/β-catenin通路及胚胎体轴形成之关系。EIF4A3及Wnt/β-catenin通路既与生物体正常生命过程又与人类疾病包括癌症的发生密切相关，预期结果一方面进一步拓宽和加深对EIF4A家族功能的认识，另一方面为深入解析Wnt信号通路重要且复杂的调控网络提供重要参考依据。

在经典的Wnt/β-catenin信号通路中，β-catenin和Tcf/Lefs的相互作用是至关重要的，其形成的转录激活复合物促进多个靶基因的表达。然而，在Wnt激活或者沉默的情况下，该转录体活性的调控还存在许多未知机制。真核起始因子4A3（EIF4A3）是一个ATP依赖的DEAD家族的RNA解旋酶，其作为外显子连接复合物（EJC）的重要组成成分，参与调节一系列的RNA转录后调控过程。我们的研究表明，EIF4A3还作为一个Wnt抑制因子参与调控该通路。EIF4A3通过结合 β-catenin和Tcf，调控转录复合体的形成，进而发挥减弱Wnt/β-catenin信号通路的作用。当Wnt信号通路激活时，EIF4A3从β-catenin 和Tcf/Lefs复合上解离下来，通过增强 β-catenin 和Tcf/Lefs的相互作用而增加Wnt信号通路活性。在斑马鱼胚胎中，eif4a3缺失会导致Wnt /β-catenin信号的激活，表现出抑制背部组织的发育和前神经外胚层的形成。相反，eif4a3的过表达会降低Wnt /β-catenin信号传导进而抑制了在原肠胚形成前背部组织者的形成。我们的研究结果揭示了EIF4A3在抑制Wnt信号通路和调节斑马鱼胚胎发育中的新作用。