Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan.
Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
Biochem Biophys Res Commun. 2018 Jun 7;500(3):583-588. doi: 10.1016/j.bbrc.2018.04.105. Epub 2018 Apr 22.
During oogenesis, oocytes prepare for embryonic development following fertilization. The mechanisms underlying this process are still unknown. Recently, it has been suggested that a loosened chromatin structure is involved in pluripotency and totipotency in embryonic stem (ES) cells and early preimplantation embryos, respectively. Here, we explored chromatin looseness in oocytes by fluorescence recovery after photobleaching (FRAP) using enhanced green fluorescent protein-tagged histone H2B. The results indicated that the chromatin in growing oocytes was already highly loosened to a level comparable to that in early preimplantation embryos. To elucidate the mechanism underlying the loosened chromatin structure in oocytes, we focused on chromodomain helicase DNA binding protein 9 (Chd9), which is highly expressed in growing oocytes. The oocytes from Chd9 knockout mice (Chd9) generated using the CRISPR/Cas9 system exhibited a less loosened chromatin structure than that of wild-type mice, suggesting that Chd9 is involved in the loosened chromatin structure in growing oocytes. These results suggest that a loosened chromatin structure, which is mediated by Chd9, is a prerequisite for the acquisition of totipotency after fertilization.
在卵子发生过程中，卵子为受精后的胚胎发育做准备。这一过程的机制尚不清楚。最近，有人提出，松散的染色质结构分别涉及胚胎干细胞（ES 细胞）和早期胚胎的多能性和全能性。在这里，我们通过使用增强型绿色荧光蛋白标记的组蛋白 H2B 的光漂白后荧光恢复（FRAP）来研究卵母细胞中的染色质松散情况。结果表明，生长中的卵母细胞的染色质已经高度松散，达到与早期胚胎植入前相当的水平。为了阐明卵母细胞中松散染色质结构的机制，我们专注于高度表达于生长中的卵母细胞中的染色质解旋酶 DNA 结合蛋白 9（Chd9）。使用 CRISPR/Cas9 系统生成的 Chd9 敲除小鼠（Chd9）的卵母细胞表现出比野生型小鼠更松散的染色质结构，表明 Chd9 参与了生长中的卵母细胞中松散染色质结构的形成。这些结果表明，由 Chd9 介导的松散染色质结构是受精后获得全能性的先决条件。
