Wang Xiaoyi, Pepling Melissa E
Department of Biology, Syracuse University, Syracuse, NY, United States.
Front Cell Dev Biol. 2021 May 20;9:667306. doi: 10.3389/fcell.2021.667306. eCollection 2021.
In female mammals, meiotic prophase one begins during fetal development. Oocytes transition through the prophase one substages consisting of leptotene, zygotene, and pachytene, and are finally arrested at the diplotene substage, for months in mice and years in humans. After puberty, luteinizing hormone induces ovulation and meiotic resumption in a cohort of oocytes, driving the progression from meiotic prophase one to metaphase two. If fertilization occurs, the oocyte completes meiosis two followed by fusion with the sperm nucleus and preparation for zygotic divisions; otherwise, it is passed into the uterus and degenerates. Specifically in the mouse, oocytes enter meiosis at 13.5 days post coitum. As meiotic prophase one proceeds, chromosomes find their homologous partner, synapse, exchange genetic material between homologs and then begin to separate, remaining connected at recombination sites. At postnatal day 5, most of the oocytes have reached the late diplotene (or dictyate) substage of prophase one where they remain arrested until ovulation. This review focuses on events and mechanisms controlling the progression through meiotic prophase one, which include recombination, synapsis and control by signaling pathways. These events are prerequisites for proper chromosome segregation in meiotic divisions; and if they go awry, chromosomes mis-segregate resulting in aneuploidy. Therefore, elucidating the mechanisms regulating meiotic progression is important to provide a foundation for developing improved treatments of female infertility.
在雌性哺乳动物中，减数分裂前期I始于胎儿发育阶段。卵母细胞依次经历细线期、偶线期和粗线期等前期I的各个亚阶段，最终停滞在双线期亚阶段，在小鼠中停滞数月，在人类中停滞数年。青春期后，促黄体生成素诱导一群卵母细胞排卵并恢复减数分裂，推动从减数分裂前期I向中期II的进程。如果发生受精，卵母细胞完成减数分裂II，随后与精核融合并为合子分裂做准备；否则，它会进入子宫并退化。具体在小鼠中，卵母细胞在交配后13.5天进入减数分裂。随着减数分裂前期I的进行，染色体找到其同源配对物，发生联会，在同源染色体之间交换遗传物质，然后开始分离，但在重组位点仍保持连接。在出生后第5天，大多数卵母细胞已到达前期I的双线期晚期（或核网期）亚阶段，它们在该阶段一直停滞直至排卵。本综述重点关注控制减数分裂前期I进程的事件和机制，包括重组、联会以及信号通路的调控。这些事件是减数分裂中染色体正确分离的先决条件；如果出现差错，染色体会错误分离导致非整倍体。因此，阐明调节减数分裂进程的机制对于为改善女性不孕症治疗方法奠定基础具有重要意义。
