Department of Reproductive Medicine, Peking University Shenzhen Hospital, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen, China.
State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
J Cell Physiol. 2020 Oct;235(10):7136-7145. doi: 10.1002/jcp.29612. Epub 2020 Feb 6.
Mammalian cyclin A1 is prominently expressed in testis and essential for meiosis in the male mouse, however, it shows weak expression in ovary, especially during oocyte maturation. To understand why cyclin A1 behaves in this way in the oocyte, we investigated the effect of cyclin A1 overexpression on mouse oocyte meiotic maturation. Our results revealed that cyclin A1 overexpression triggered meiotic resumption even in the presence of germinal vesicle breakdown inhibitor, milrinone. Nevertheless, the cyclin A1-overexpressed oocytes failed to extrude the first polar body but were completely arrested at metaphase I. Consequently, cyclin A1 overexpression destroyed the spindle morphology and chromosome alignment by inducing premature separation of chromosomes and sister chromatids. Therefore, cyclin A1 overexpression will prevent oocyte maturation although it can promote meiotic resumption. All these results show that decreased expression of cyclin A1 in oocytes may have an evolutional significance to keep long-lasting prophase arrest and orderly chromosome separation during oocyte meiotic maturation.
哺乳动物细胞周期蛋白 A1 在睾丸中表达明显，对雄性小鼠的减数分裂至关重要，但在卵巢中表达较弱，尤其是在卵母细胞成熟过程中。为了了解卵母细胞中细胞周期蛋白 A1 为何表现出这种方式，我们研究了细胞周期蛋白 A1 过表达对小鼠卵母细胞减数分裂成熟的影响。我们的结果表明，即使存在生发泡破裂抑制剂米力农，细胞周期蛋白 A1 过表达也会触发减数分裂恢复。然而，细胞周期蛋白 A1 过表达的卵母细胞未能排出第一极体，但完全停滞在第一次减数分裂中期。因此，细胞周期蛋白 A1 过表达通过诱导染色体和姐妹染色单体的过早分离，破坏了纺锤体形态和染色体排列。因此，尽管细胞周期蛋白 A1 过表达可以促进减数分裂恢复，但它会阻止卵母细胞成熟。所有这些结果表明，卵母细胞中细胞周期蛋白 A1 的表达减少可能具有进化意义，可在卵母细胞减数分裂成熟过程中保持长期的前期阻滞和有序的染色体分离。
