Abstract：
The actomyosin cortex is an active material that generates force to drive shape changes via cytoskeletal remodeling. Cytokinesis is the essential cell division event during which a cortical actomyosin ring closes to separate two daughter cells. Our active gel theory predicted that actomyosin systems controlled by a biochemical oscillator and experiencing mechanical strain would exhibit complex spatiotemporal behavior. To test whether active materials in vivo exhibit spatiotemporally complex kinetics, we imaged the C. elegans embryo with unprecedented temporal resolution and discovered that sections of the cytokinetic cortex undergo periodic phases of acceleration and deceleration. Contractile oscillations exhibited a range of periodicities, including those much longer periods than the timescale of RhoA pulses, which was shorter in cytokinesis than in any other biological context. Modifying mechanical feedback in vivo or in silico revealed that the period of contractile oscillation is prolonged as a function of the intensity of mechanical feedback. Fast local ring ingression occurs where speed oscillations have long periods, likely due to increased local stresses and, therefore, mechanical feedback. Fast ingression also occurs where material turnover is high, in vivo and in silico. We propose that downstream of initiation by pulsed RhoA activity, mechanical feedback, including but not limited to material advection, extends the timescale of contractility beyond that of biochemical input and, therefore, makes it robust to fluctuations in activation. Circumferential propagation of contractility likely allows for sustained contractility despite cytoskeletal remodeling necessary to recover from compaction. Thus, like biochemical feedback, mechanical feedback affords active materials responsiveness and robustness.
摘要：
肌动球蛋白皮质是通过细胞骨架重塑产生驱动形状变化的力的活性材料。细胞分裂是重要的细胞分裂事件，在此期间皮质肌动球蛋白环关闭以分离两个子细胞。我们的主动凝胶理论预测，由生化振荡器控制并经历机械应变的肌动球蛋白系统将表现出复杂的时空行为。为了测试体内活性材料是否表现出时空复杂的动力学，我们以前所未有的时间分辨率对秀丽隐杆线虫胚胎进行成像，并发现细胞动力学皮质部分经历了加速和减速的周期性阶段。收缩振荡表现出一系列周期性，包括那些比RhoA脉冲的时间尺度长得多的周期，胞质分裂比任何其他生物学背景都短。在体内或计算机上修改机械反馈表明，收缩振荡的时间随机械反馈的强度而延长。在速度振荡周期较长的情况下，会发生快速局部振铃，可能是由于局部应力增加，因此,机械反馈。在材料周转率很高的地方也会发生快速侵入，在体内和硅。我们建议在脉冲RhoA活性引发的下游，机械反馈,包括但不限于材料平流，将收缩性的时间尺度扩展到生化输入的时间尺度之外，因此,使其对激活的波动具有鲁棒性。尽管需要从压实中恢复细胞骨架重塑，但收缩性的周向传播可能允许持续的收缩性。因此，比如生化反馈，机械反馈提供活性材料的响应性和鲁棒性。
