Laboratory for Chromosome Segregation, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan.
Laboratory for Chromosome Segregation, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan.
Dev Cell. 2017 May 8;41(3):287-298.e4. doi: 10.1016/j.devcel.2017.04.009.
Chromosome segregation during meiosis in oocytes is error prone. The uniquely large cytoplasmic size of oocytes, which provides support for embryogenesis after fertilization, might be a predisposing factor for meiotic errors. However, this hypothesis remains unproven. Here, we show that cytoplasmic size affects the functionality of the acentrosomal spindle. Artificially decreasing the cytoplasmic size in mouse oocytes allows the acentrosomal spindle poles to have a better-focused distribution of microtubule-organizing centers and to biorient chromosomes more efficiently, whereas enlargement of the cytoplasmic size has the opposite effects. Moreover, we found that the cytoplasmic size-dependent dilution of nuclear factors, including anaphase inhibitors that are preformed at the nuclear membrane, limits the spindle's capacity to prevent anaphase entry with misaligned chromosomes. The present study defines a large cytoplasmic volume as a cell-intrinsic feature linked to the error-prone nature of oocytes. This may represent a trade-off between meiotic fidelity and post-fertilization developmental competence.
卵母细胞减数分裂过程中的染色体分离容易出错。卵母细胞独特的大细胞质体积为受精后胚胎发生提供支持，这可能是减数分裂错误的一个易感因素。然而，这一假说尚未得到证实。在这里，我们表明细胞质大小会影响无中心体纺锤体的功能。人为减小小鼠卵母细胞的细胞质大小可以使无中心体纺锤体极更好地集中微管组织中心的分布，并更有效地使染色体双定向，而细胞质大小的增大则会产生相反的效果。此外，我们发现，包括在核膜上预先形成的后期抑制剂在内的核因子的细胞质大小依赖性稀释，限制了纺锤体防止染色体未对准进入后期的能力。本研究将大的细胞质体积定义为与卵母细胞易出错性质相关的细胞内在特征。这可能是减数分裂保真度和受精后发育能力之间的权衡。
