Essential role of germinal vesicle material in the meiotic cell cycle of Xenopus oocytes
Essential role of germinal vesicle material in the meiotic cell cycle of Xenopus oocytes
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DOI：
10.1073/pnas.95.8.4392
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发表时间：
1998-04-14
影响因子：
11.1
通讯作者：
Sagata, N
中科院分区：
文献类型：
--
作者：
Iwashita, J;Hayano, Y;Sagata, N
在几乎所有的动物物种中，未成熟的卵母细胞在第一次减数分裂前期自然地被捕获，具有称为生殖囊泡的大核。许多先前的研究表明，成熟/M期促进因子（MPF）（半定量细胞学方法测定）和其他一些成熟事件的激活基本上正常发生在许多两栖动物物种和小鼠的去核卵母细胞。因此，近三十年来，人们普遍认为，核物质是MPF激活和减数分裂细胞周期在脊椎动物卵母细胞。在这里，我们通过研究组蛋白H1激酶的活性和MPF的分子形式在实验操作的非洲爪蟾卵母细胞的挑战这一观点。我们认为注射核物质的卵母细胞比未注射的对照卵母细胞经历更快的MPF激活和成熟。相反，去核卵母细胞，不像有核的同行，只经历弱MPF激活在减数分裂I和没有检测到的MPF再激活在减数分裂II，后者伴随抑制性酪氨酸磷酸化的cdc 2激酶，MPF的催化亚基。这些结果强烈认为，核物质是不可缺少的减数分裂细胞周期，特别是MPF重新激活（或cdc 2酪氨酸去磷酸化）进入减数分裂II，在爪蟾卵母细胞。因此，可能需要重新考虑传统和普遍的观点。
In almost all animal species, immature oocytes are arrested naturally in the first meiotic prophase, with a large nucleus called the germinal vesicle. A number of previous studies showed that both activation of maturation/M phase-promoting factor (MPF) (assayed by semiquantitative cytological methods) and some other maturational events occur essentially normally in enucleated oocytes from many amphibian species and mice. Hence, for nearly three decades, it has generally been believed that nuclear material is dispensable for MPF activation and the meiotic cell cycle in vertebrate oocytes. Here, we have challenged this view by examining the histone H1 kinase activities and the molecular forms of MPF in experimentally manipulated Xenopus oocytes. We shelf that oocytes injected with nuclear material undergo much more rapid MPF activation and maturation than uninjected control oocytes. Conversely, enucleated oocytes, unlike nucleated counterparts, undergo only weak MPF activation in meiosis I and no detectable MPF reactivation in meiosis II, the latter accompanying inhibitory tyrosine phosphorylation of cdc2 kinase, the catalytic subunit of MPF. These results argue strongly that nuclear material is indispensable for the meiotic cell cycle, particularly MPF reactivation (or cdc2 tyrosine dephosphorylation) on entry into meiosis II, in Xenopus oocytes. The classical and general view may thus need reconsideration.