小鼠早期胚胎在外源信号、内源因子及表观遗传调控的综合作用下，从具有多能性的上胚层特化形成外、中、内三个胚层。在该过程中，调控元件及其活性状态发挥着重要的调控作用。我们前期的研究鉴定出一个外胚层特异性增强子Ect2，然而其在小鼠胚胎发育中的功能和作用机制还不清楚。为研究增强子Ect2的体内功能及作用机制，我们构建了Ect2敲除小鼠胚胎干细胞系和小鼠品系，以及Ect2-pHsp68-CreERT2和Ect2-pHsp68-turboGFP转基因小鼠品系。本项目旨在通过对Ect2敲除小鼠胚胎干细胞及不同发育阶段胚胎的表型分析，阐明该增强子在小鼠胚胎发育过程中的作用，明确并验证增强子Ect2的调控网络和作用机制；通过对转基因小鼠中Ect2阳性细胞谱系的追踪，解析外胚层细胞谱系命运决定过程的分子机制。项目成果将大大加深人们对哺乳动物早期胚胎发育过程及调控机制的认识。

The early embryonic development of vertebrates is tightly regulated by multiple factors. Under the coordinated action of exogenous signals, endogenous factors and epigenetic regulation, embryos are gradually specialized from the pluripotent epiblast cells to form three germ layers of the ectoderm, mesoderm, and endoderm. It has been reported that the chromatin states of regulatory elements play critical roles in the establishment of cell lineage and the determination of germ layer fate. Our previous study identified an enhancer-Ect2, which exhibits ectoderm-specific activity in the gastrula, and exhibits severe neural differentiation abnormalities in Ect2 knockout embryonic stem cells. However, how Ect2 functions in vivo and how Ect2 affects neural differentiation still remain largely unknown. To answer this question, we have established Ect2 knockout mouse stem cell lines, knockout mouse lines，Ect2-Hsp68 minimal promoter-CreERT2 and Ect2-Hsp68 minimal promoter-turboGFP transgenic mouse lines. In this project, we aim to elucidate the in vivo role and functional mechanism of Ect2 enhancer by analyzing the transcriptomic and epigenomic changes from Ect2 knockout stem cell and mouse embryo; depict the development hierarchical tree of ectoderm lineage by tracing the Ect2 enhancer positive precursor cells. The result of this project will broaden the current understanding of mammalian early embryonic development and related regulatory elements-mediated regulatory networks.