H3K9me3与H3K27me3对猪体细胞重编程影响机制

表观遗传修饰异常是体细胞核移植胚胎发育能力低下的重要原因之一，而降低DNA甲基化或提高组蛋白乙酰化水平并不能有效地解决这一问题。最近的研究表明H3K9me3的异常修饰是小鼠与人的体细胞核移植胚胎发育效率低下的主要原因，通过导入其去甲基化酶能够显著提高核移植胚胎发育效率。本课题组的前期工作发现猪体细胞核移植胚胎2细胞与4细胞期H3K9me3水平显著高于IVF胚胎；同时，核移植胚胎中H3K27me3也呈现高的修饰水平，而降低其水平后能够显著地提高核移植胚胎囊胚率。基于此，本课题拟评价H3K9me3对核移植胚胎发育的影响，探索H3K9me3与H3K27me3修饰相关因子表达模式，挖掘被H3K9me3或H3K27me3修饰调节的关键发育基因，藉此探讨H3K9me3与H3K27me3是否为猪体细胞重编程的关键修饰位点，以期加深对猪体细胞重编程机制的理解。

It has been proposed that the aberrant histone epigenetic reprogramming during early embryonic development is one of the major reason for the low efficiency of somatic cell nuclear transfer (SCNT) technique, whereas effects of decreasing the DNA methylation or increasing the histone acetylation level, on clone efficiency are limited. This prompts researchers to investigate detailed mechanism of epigenetic reprogramming. There are reports showed that aberrant H3K9me3 modification is the main reason for low efficiency of mouse and human SCNT embryos, and removal of H3K9me3 greatly improves SCNT efficiency. Our group have found that H3K9me3 level is higher at 2-cell and 4-cell stages in SCNT embryos than IVF embryos in pig. Meanwhile, our study indicates that H3K27me3 level is higher in somatic cells and SCNT embryos than IVF embryos, and the reduction of H3K27me3 level in somatic cells or SCNT embryo both can significantly improve development efficiency of cloned embryo. Therefore, the current proposed study aims to determine whether excessive H3K9me3 and H3K27me3 modification was the main reason for aberrant development of SCNT embryo. For this purpose, we will determine the abundance of key methyltransferases and demethylases of H3K9me3/H3K27me3 in preimplantation SCNT and IVF embryo. Key developmental factors or related signal pathways in preimplantation embryo which repressed by H3K9me3 and H3K27me3 will be identified and verified. The answer of this question would help clarifying the mechanism of somatic cell reprogramming in pig.