LET-99相关的空间限制的主动力发生器使主轴的位置鲁棒
LET-99-dependent spatial restriction of active force generators makes spindle's position robust
摘要：
在秀丽隐杆线虫受精卵的不对称分裂过程中，极性线索的分布和子细胞命运取决于有丝分裂纺锤体的正确定位，这是由定心力和皮质拉力共同作用的结果。通过后期纺锤体摇摆揭示，这些拉力由力发生器动力学调节，这反过来又是有丝分裂进程的结果。我们发现了一个新的，额外的，这些力量的调节主轴的位置。它控制着皮层的星形微管的可用性，主动力发生器可以拉动它。重要的是，这种位置控制依赖于极性依赖性LET-99皮质带，其将发生器限制或集中到后新月形。我们将这种控制归因于皮层的微管动力学。事实上，在绘制皮质接触，我们发现了中心体皮质距离和微管接触密度之间的相关性。反过来，它调节拉力发生器的活动。我们模拟了这种控制，预测和实验验证，后新月形范围控制的后期振荡开始，除了有丝分裂的进展。最后，我们建议，空间限制力发生器后新月设置主轴的最终位置，反映极性通过LET-99依赖限制力发生器后新月。这种调节叠加力发生器的持续合成能力。这种新的控制赋予低依赖性微管和主动力发生器的确切数字或动力学，只要它们超过后位移所需的阈值。有趣的是，这种鲁棒性起源于细胞力学，而不是生物化学网络。
英文摘要：
During the asymmetric division of the Caenorhabditis elegans nematode zygote, the polarity cues distribution and daughter cell fates depend on the correct positioning of the mitotic spindle, which results from both centering and cortical pulling forces. Revealed by anaphase spindle rocking, these pulling forces are regulated by the force generator dynamics, which are in turn consequent of mitotic progression. We found a novel, additional, regulation of these forces by the spindle position. It controls astral microtubule availability at the cortex, on which the active force generators can pull. Importantly, this positional control relies on the polarity dependent LET-99 cortical band, which restricts or concentrates generators to a posterior crescent. We ascribed this control to the microtubule dynamics at the cortex. Indeed, in mapping the cortical contacts, we found a correlation between the centrosome-cortex distance and the microtubule contact density. In turn, it modulates pulling force generator activity. We modelled this control, predicting and experimentally validating that the posterior crescent extent controlled where the anaphase oscillations started, in addition to mitotic progression. Finally, we propose that spatially restricting force generator to a posterior crescent sets the spindle's final position, reflecting polarity through the LET-99 dependent restriction of force generators to a posterior crescent. This regulation superimposes that of force generator processivity. This novel control confers a low dependence on microtubule and active force generator exact numbers or dynamics, provided that they exceed the threshold needed for posterior displacement. Interestingly, this robustness originates in cell mechanics rather than biochemical networks.
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