Biochemistry and Molecular Biology Department, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205.
Mol Biol Cell. 2020 Jun 1;31(12):1206-1217. doi: 10.1091/mbc.E19-12-0701. Epub 2020 Apr 8.
Errors during meiotic resumption in oocytes can result in chromosome missegregation and infertility. Several cell cycle kinases have been linked with roles in coordinating events during meiotic resumption, including polo-like kinases (PLKs). Mammals express four kinase-proficient PLKs (PLK1-4). Previous studies assessing the role of PLK1 have relied on RNA knockdown and kinase inhibition approaches, as null mutations are embryonically lethal. To further assess the roles of PLK1 during meiotic resumption, we developed a conditional knockout (cKO) mouse to specifically mutate in oocytes. Despite normal oocyte numbers and follicle maturation, cKO mice were infertile. From analysis of meiotic resumption, cKO oocytes underwent nuclear envelope breakdown with the same timing as control oocytes. However, cKO oocytes failed to form compact bivalent chromosomes, and localization of cohesin and condensin were defective. Furthermore, cKO oocytes either failed to organize α-tubulin or developed an abnormally small bipolar spindle. These abnormalities were attributed to aberrant release of the microtubule organizing center (MTOC) linker protein, C-NAP1, and the failure to recruit MTOC components and liquid-like spindle domain (LISD) factors. Ultimately, these defects result in meiosis I arrest before homologous chromosome segregation.
卵母细胞减数分裂恢复过程中的错误可导致染色体错误分离和不孕。几种细胞周期激酶与减数分裂恢复过程中的协调事件有关，包括 Polo 样激酶（PLK）。哺乳动物表达四种激酶活性的 PLK（PLK1-4）。以前评估 PLK1 作用的研究依赖于 RNA 敲低和激酶抑制方法，因为缺失突变是胚胎致死的。为了进一步评估 PLK1 在减数分裂恢复过程中的作用，我们开发了一种条件敲除（cKO）小鼠，专门在卵母细胞中突变。尽管卵母细胞数量和卵泡成熟正常，但 cKO 小鼠是不育的。从减数分裂恢复的分析来看，cKO 卵母细胞与对照卵母细胞具有相同的核膜破裂时间。然而，cKO 卵母细胞未能形成紧密的二价染色体，并且黏连蛋白和凝聚素的定位有缺陷。此外，cKO 卵母细胞要么未能组织微管组织中心（MTOC）连接蛋白 α-微管蛋白，要么发育出异常小的双极纺锤体。这些异常归因于微管组织中心（MTOC）连接蛋白 C-NAP1 的异常释放，以及无法募集 MTOC 成分和液态纺锤体域（LISD）因子。最终，这些缺陷导致同源染色体分离前的第一次减数分裂停滞。
