REGULATION OF THE APPEARANCE OF DIVISION ASYNCHRONY AND MICROTUBULE-DEPENDENT CHROMOSOME CYCLES IN XENOPUS-LAEVIS EMBRYOS
REGULATION OF THE APPEARANCE OF DIVISION ASYNCHRONY AND MICROTUBULE-DEPENDENT CHROMOSOME CYCLES IN XENOPUS-LAEVIS EMBRYOS
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DOI：
10.1006/dbio.1995.1280
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发表时间：
1995-10-01
影响因子：
2.7
通讯作者：
MASUI, Y
中科院分区：
文献类型：
--
作者：
CLUTE, P;MASUI, Y
从非洲爪蟾胚胎分离出的动物帽卵裂球在第12次卵裂或第13个细胞周期前大部分是同步分裂的，但在随后的囊胚中过渡期（MET）中分裂为非同步分裂，同时染色体周期依赖于微管并在有丝分裂中被诺可唑抑制。为了研究这些细胞周期控制变化的原因，我们观察了核质比（N/C）因合子收缩或延迟成核而改变的胚胎分离的动物帽卵裂球的分裂同同性，并比较了它们在存在和不存在诺可唑的情况下的有丝分裂指数。因此，我们发现，当NIC达到32细胞胚胎的动物卵裂球的128 ~ 256倍时，总是开始异步分裂，对应于正常胚胎的第12和第13个周期，而同步周期的数量则是可变的，根据初始N/C的不同，从9到14不等。α -amanitin或环己亚胺治疗不改变同步循环次数。然而，无论初始N/C如何，诺可达唑处理的卵裂球在第5次卵裂后3 ~ 5小时的有丝分裂指数首次超过对照的时间保持不变。因此，卵裂球的染色体周期首先在可变NIC时对nocodazole敏感，其范围为32细胞胚胎的动物卵裂球的8至1024倍。nocodazole敏感性出现的时间不受α -amanitin治疗的影响，而在环己亚胺治疗后明显延迟。这些结果表明，分裂不同步的开始是N/ c依赖的，而微管依赖的鳗鱼周期的发展是年龄依赖的，很可能是由储存的mrna的翻译编程的。(C) 1995学术出版社，Inc。
Divisions of animal-cap blastomeres dissociated from Xenopus laevis embryos are synchronous mostly up to 12th cleavage or the 13th cell cycle, but become asynchronous afterward, during the midblastula transition (MET), and at the same time, chromosome cycles become microtubule-dependent and are arrested in mitosis if treated with nocodazole. To investigate causes for these changes in cell-cycle control, we observed division synchrony in animal-cap blastomeres dissociated from embryos whose nucleocytoplasmic ratio (N/C) had been altered by constriction of zygotes or by delaying nucleation into zygote halves and compared their mitotic indices in the presence and absence of nocodazole. Thus, we found that asynchronous divisions always commenced when NIC reached the value of 128 to 256 times that of an animal blastomere of the 32-cell embryo, corresponding to the 12th and 13th cycles of a normal embryo, while the number of synchronous cycles became variable, ranging from 9 to 14, depending on the initial N/C. Treatment with alpha-amanitin or cycloheximide did not alter the number of synchronous cycles. However, the time at which the mitotic index of nocodazole-treated blastomeres first exceeded that of control remained constant, at 3 to 5 hr after 5th cleavage, regardless of the initial N/C. Thus, chromosome cycles of blastomeres first became sensitive to nocodazole at a variable NIC, ranging from 8 to 1024 times that of an animal blastomere of the 32-cell embryo. The timing of the appearance of nocodazole sensitivity was unaffected by alpha-amanitin treatment, whereas it was markedly delayed following cycloheximide treatment. These results suggest that the commencement of division asynchrony is N/C-dependent, whereas the development of microtubule-dependent eel cycles is age-dependent, most likely being programmed by the translation of stored mRNAs. (C) 1995 Academic Press, Inc.