McNally Karen L, McNally Francis J
Section of Molecular and Cellular Biology, 149 Briggs Hall, University of California, Davis, CA 95616, USA.
Dev Biol. 2005 Jun 1;282(1):218-30. doi: 10.1016/j.ydbio.2005.03.009.
Oocytes from most animals arrest twice during the meiotic cell cycle. The universally conserved prophase I arrest is released by a maturation hormone that allows progression to a second arrest point, typically metaphase I or II. This second arrest allows for short-term storage of fertilization-competent eggs and is released by signaling that occurs during fertilization. Nematodes are unique in that the maturation hormone is secreted by sperm rather than by the mother's somatic tissues. We have investigated the nature of the second arrest in matured but unfertilized Caenorhabditis elegans embryos using time-lapse imaging of GFP-tubulin or GFP-histone. Unfertilized embryos completed anaphase I but did not form polar bodies or assemble meiosis II spindles. Nevertheless, unfertilized embryos assembled female pronuclei at the same time as fertilized embryos. Analysis of embryos fertilized by sperm lacking the SPE-11 protein indicated that fertilization promotes meiotic cytokinesis through the SPE-11 protein but assembly of the meiosis II spindle is initiated through an SPE-11-independent pathway.
大多数动物的卵母细胞在减数分裂细胞周期中会停滞两次。普遍保守的减数分裂前期I停滞会被一种成熟激素解除，该激素使细胞能够进入第二个停滞点，通常是中期I或中期II。这第二个停滞点允许对具备受精能力的卵子进行短期储存，并在受精过程中通过信号传导被解除。线虫的独特之处在于，成熟激素是由精子而非母体的体细胞组织分泌的。我们使用GFP微管蛋白或GFP组蛋白的延时成像技术，研究了成熟但未受精的秀丽隐杆线虫胚胎中第二个停滞点的性质。未受精的胚胎完成了后期I，但没有形成极体，也没有组装减数分裂II纺锤体。然而，未受精的胚胎与受精胚胎同时组装了雌性原核。对由缺乏SPE-11蛋白的精子受精的胚胎进行分析表明，受精通过SPE-11蛋白促进减数分裂胞质分裂，但减数分裂II纺锤体的组装是通过一条不依赖SPE-11的途径启动的。
