Fulka J, First N L, Fulka1 J, Moor R M
The Institute of Animal Production, CS-104 01 Prague 10, Czech Republic.
Hum Reprod. 1999 Jun;14(6):1582-7. doi: 10.1093/humrep/14.6.1582.
The high incidence of chromosomally abnormal human embryos is frequently assumed to be due to a lack of checkpoint controls operating during early embryogenesis. In our study we have analysed when these mechanisms first become functional. Mouse oocytes treated in late metaphase I with either of two different cyclin-dependent kinase inhibitors [butyrolactone 1 (BL1) or 6-dimethylaminopurine (6-DMAP)] form nuclei in the cytoplasm. BL1-treated eggs enter S-phase at 16-18 h post-treatment and, after completion of DNA synthesis, cleave to 2-cell stage embryos. 6-DMAP treatment results in the rapid initiation of DNA synthesis, its completion by 12 h and then arrest in the G2 phase. Thus, two different cell cycle stages can be obtained at the same time point after the initiation of treatment: G1- after BL1 and G2-staged nuclei after 6-DMAP treatment. That this approach greatly facilitates cell cycle studies has been shown by analysing checkpoint function during the first division. Whilst G2-staged eggs enter M phase within 2-3 h when 6-DMAP is washed out, the onset of M phase is delayed after their fusion to G1 (BL1) cells. Here M phase occurs only after the less advanced nucleus completes DNA replication. Our results indicate that checkpoints in mammalian eggs are functional during the first mitotic cycle.
人类胚胎染色体异常的高发生率通常被认为是由于早期胚胎发育过程中缺乏检查点控制机制。在我们的研究中，我们分析了这些机制何时首次发挥作用。在中期I后期用两种不同的细胞周期蛋白依赖性激酶抑制剂[丁内酯1（BL1）或6-二甲基氨基嘌呤（6-DMAP）]处理的小鼠卵母细胞在细胞质中形成细胞核。经BL1处理的卵在处理后16 - 18小时进入S期，完成DNA合成后，分裂为2细胞期胚胎。6-DMAP处理导致DNA合成迅速启动，在12小时完成，然后停滞在G2期。因此，在处理开始后的同一时间点可以获得两个不同的细胞周期阶段：BL1处理后的G1期和6-DMAP处理后的G2期细胞核。通过分析第一次分裂期间的检查点功能表明，这种方法极大地促进了细胞周期研究。当6-DMAP被洗脱时，G2期的卵在2 - 3小时内进入M期，而它们与G1（BL1）期细胞融合后，M期的开始延迟。在这里，M期仅在发育较晚的细胞核完成DNA复制后才会发生。我们的结果表明，哺乳动物卵中的检查点在第一次有丝分裂周期中发挥作用。
