Epigenetic Regulation in Development and Differentiation

表观遗传状态的建立对多细胞生物的发育和分化至关重要。在本项目中，我们对表观遗传状态的建立进行了以下三个方面的研究。早期胚胎DNA甲基化调控因子PGC7/ Stella的功能。PGC7/ Stella具有阻止早期胚胎“活跃的DNA去甲基化”的作用。我们发现PGC/ Stella与H3K9me2（组蛋白H3的二甲基赖氨酸9）的结合对该功能至关重要。在这个项目的过程中，Tet蛋白通过将5-甲基胞嘧啶转化为5-羟甲基胞嘧啶，在活性DNA去甲基化中发挥关键作用。基于这些数据，我们发现早期胚胎中最丰富的Tet蛋白Tet-3与染色质的结合受到PGC7.2的抑制。利用体外胚胎干细胞造血分化诱导系统分析GATA-1转录因子的功能。GATA-1在不同时间点的控制表达表明，该因子在不同时间点的功能差异较大，其不同作用受表观遗传机制控制。我们发现GS细胞（种系干细胞）是研究piRNA生物发生的一个非常有用的资源，并且piRNA产生的初始阶段是在细胞中进行的。利用GS细胞，我们成功地鉴定了一种参与piRNA生物发生的蛋白。此外，我们建立了一个新的实验系统来诱导转基因小鼠的piRNA和随后的DNA甲基化。

Establishment of epigenetic state is critically important for development and differentiation of multicellular organisms. In this project, we carried out following three issues on the establishment of epigenetic status.1. Function of PGC7/ Stella, a regulator of DNA methylation in early embryos.: PGC7/ Stella has the effect to prevent" active DNA demethylation" in early embryos. We identified that the binding of PGC/ Stella to H3K9me2(dimethylated lysine 9 of histone H3) is critically important for the function. During the course of this project, Tet protein plays critical roles in active DNA demethylation by converting 5-methyl cytosine to 5-hydroxymethyl cytosine. Based on this data, we revealed that the binding of Tet-3, the most abundant Tet protein in early embryos, to chromatin is inhibited by PGC7.2. We analyzed the function of GATA-1 transcription factor using in vitro hematopoietic differentiation induction system from ES cells. Controlled expression of GATA-1 at different time points showed that the function of the factor is quite varied dependent on the time point and its different roles were controlled by epigenetic mechanisms.3. We find that GS cells(Germline stem cells) are a quite useful resource for studying the biogenesis of piRNA and that the initial phase of piRNA production is carried out in the cells. Using GS cells, we succeeded to identify a protein involved in piRNA biogenesis. In addition, we established a novel experimental system to induce piRNA and subsequent DNA methylation in the transgenic mice.