原肠运动过程中外胚层的命运决定及表观遗传调控

Early mammal embryonic development is very important for proper patterning of animal bodies. All the specific tissues and organs are derived from three germ layers which are generated during embryo gastrulation. Ectoderm is one of the three classic germ layers in the early mouse embryo, with the capacity to develop into both the central nervous system and epidermis. Because it is a transient phase of development with few molecular markers, the early ectoderm is the least understood germ layer in mouse embryonic development. In our study, we identified E7.0 as a key developmental stage when ectoderm cells exist transiently in the anterior/proximal domain of the ectodermal layer. Through the combination of laser microdissection and single cell sequencing technology, we analyzed the whole transcriptome of mouse embryo at E7.0. We compared the global transcriptome changes with important epigenetic modifiers and characterized the regulation network directing ectoderm development. Furthermore, the ectoderm cell line was established as an in vitro cell model to study the molecular mechanism underlying the ectoderm lineage commitment. Next, we will carry the analysis in the early and late gastrulation stage. We will construct a temporal and spatial regulation map with high resolution for ectoderm patterning. Based on this findings, we are close to understand the signaling networks and epigenetic regulations that lead to ectoderm identity in very much details. Our study will greatly facilitate the understanding of the ectodermal layer development in early mouse embryos and provide a framework for the ectoderm-based regenerative medicine.

在小鼠胚胎发育早期，外胚层的概念已提出多年。然而到目前为止，外胚层分化和发育的内部机制仍然所知甚少。我们在体内确立了外胚层存在的位置与时期，通过激光显微切割以及单细胞测序等技术，在全基因组水平上考察和分析了外胚层的转录表达图谱。我们进一步考察了外胚层区域的表观遗传修饰与转录组之间的调控关系。同时，在体外建立了外胚层干细胞系。本项目拟在上述研究基础上，结合体内体外的实验手段，继续深入研究原肠运动过程中外胚层命运决定的重要分子机制，在全基因组水平上详细阐释表观遗传调控对外胚层模式建成的影响和分子调控。这些工作的完成将有助于加深人们对胚胎发育早期外胚层细胞谱系的认识，并对外胚层细胞命运决定的分子机制研究和外胚层干细胞的临床应用打下坚实的基础。

脊椎动物早期胚胎发育是一个受到严谨精细调控的生命过程。在小鼠胚胎发育早期的原肠运动时期，胚胎各个特定位置的细胞在迁移和分化中，受到外源信号、内源因子及表观遗传调控的综合作用，由多能性的上胚层干细胞发育为不同发育命运的外胚层、中胚层、内胚层。其中外胚层的形成对于神经系统的发育至关重要。本项目中，我们主要聚焦在小鼠原肠运动期间外胚层的命运决定过程及其表观遗传调控机制。本项目通过开发基于少量细胞的转录组和表观遗传学研究手段，全面解析了小鼠胚层发育的时空转录组图谱，深入研究了小鼠原肠运动过程中胚胎各胚层的表观遗传修饰变化模式，揭示了原肠运动时期各胚层发育过程的表观调控机制，发现了外胚层发育过程中新的调控元件，阐明了发育相关基因在原肠胚不同区域内表观调控机制的差别。并进一步结合体外细胞培养系统，研究了小鼠胚胎干细胞神经分化过程中TGFbeta信号和表观遗传调控对细胞命运决定的协同调控作用，探讨了人胚胎干细胞神经分化过程中DNA甲基化和组蛋白修饰的重要作用。本项目的研究成果将极大地加深对哺乳动物早期胚胎发育过程中分子调控机制的认识，从而推动再生医学等的发展。