Elucidation of mechanisms of germ cell reprogramming and establishment of the procedure to control epigenome.

为了加深对体细胞核移植(SCNT)效率低下的认识，我们对小鼠体细胞核移植囊胚进行了整体转录分析。在SCNT胚胎中发现的许多下调基因(21/39)位于X染色体上。当利用Xist缺失的供体细胞纠正SCNT胚胎中X连锁基因的下调时，出生率增加了8-9倍。因此，纠正SCNT特有的表观遗传错误可能会显著改善SCNT。在接下来的一系列实验中，为了了解SCNT囊胚中X染色体A7.2和F3区域(XqA7.2/F3)持续下调的原因，我们利用来自卵丘细胞的染色质免疫沉淀芯片数据，分析了抑制修饰，组蛋白H3赖氨酸9(H3K9me2)的二甲基化。结果表明，H3K9me2在XqA7.2/F3中广泛富含，并形成组织特异性区块，称为大有组织染色质K9修饰(LOCKS)。这些数据表明，XqA7.2/F3的下调是由于核移植后锁的重新编程失败所致。

To improve understanding of the low efficiency of somatic cell nuclear transfer (SCNT), we performed global transcription analysis of mouse SCNT blastocysts. Many of the downregulated genes (21/39) identified in SCNT embryos were located on the X chromosome. When the downregulation of X-linked genes in SCNT embryos was corrected by using Xist-deficient donor cells, the birth rates increased 8- to 9-fold. Thus, SCNT may be significantly improved by correcting epigenetic errors specific for SCNT.In the next series of experiments, to understand the cause of consistent downregulation in the region of A7.2 and F3 on X chromosome (XqA7.2/F3) in SCNT blastocysts, we analyzed repressive modification, dimethylation of histone H3 lysine 9 (H3K9me2), with chromatin immunoprecipitation-on-chip data from cumulus cells. The results showed that H3K9me2 was broadly enriched in XqA7.2/F3 and formed tissue-specific blocks called as large organized chromatin K9 modification (LOCKs). These data suggested that downregulation of XqA7.2/F3 was caused by failure of reprogramming of LOCKs after nuclear transfer.