Cell Architecture Laboratory, Structural Biology Center, National Institute of Genetics, Mishima 411-8540, Japan.
Department of Biological Science, Kwansei Gakuin University, Sanda 669-1337, Japan.
Mol Biol Cell. 2020 Jul 21;31(16):1765-1773. doi: 10.1091/mbc.E20-01-0058. Epub 2020 May 27.
Cell polarization is required to define body axes during development. The position of spatial cues for polarization is critical to direct the body axes. In zygotes, the sperm-derived pronucleus/centrosome complex (SPCC) serves as the spatial cue to specify the anterior-posterior axis. Approximately 30 min after fertilization, the contractility of the cell cortex is relaxed near the SPCC, which is the earliest sign of polarization and called symmetry breaking (SB). It is unclear how the position of SPCC at SB is determined after fertilization. Here, we show that SPCC drifts dynamically through the cell-wide flow of the cytoplasm, called meiotic cytoplasmic streaming. This flow occasionally brings SPCC to the opposite side of the sperm entry site before SB. Our results demonstrate that cytoplasmic flow determines stochastically the position of the spatial cue of the body axis, even in an organism like for which development is stereotyped.
细胞极化是胚胎发育过程中定义体轴的必要条件。极化的空间线索的位置对于指导体轴的形成至关重要。在受精卵中，精子衍生的原核/中心体复合物（SPCC）作为空间线索来指定前后轴。受精后大约 30 分钟，SPCC 附近的细胞皮层的收缩性被松弛，这是极化的最早迹象，称为对称性破缺（SB）。目前尚不清楚 SB 后 SPCC 的位置是如何确定的。在这里，我们表明 SPCC 会通过称为减数分裂细胞质流的细胞质全细胞流动动态漂移。这种流动偶尔会在 SB 之前将 SPCC 带到精子进入位点的对侧。我们的结果表明，细胞质流动随机决定了体轴空间线索的位置，即使在像 这样的发育模式化的生物体中也是如此。
