The Par complex dynamically polarizes to the apical cortex of asymmetrically dividing Drosophila neuroblasts where it directs fate determinant segregation. Previously we showed that apically directed cortical movements that polarize the Par complex require F-actin (Oon and Prehoda, 2019). Here we report the discovery of cortical actomyosin dynamics that begin in interphase when the Par complex is cytoplasmic but ultimately become tightly coupled to cortical Par dynamics. Interphase cortical actomyosin dynamics are unoriented and pulsatile but rapidly become sustained and apically-directed in early mitosis when the Par protein aPKC accumulates on the cortex. Apical actomyosin flows drive the coalescence of aPKC into an apical cap that is depolarized in anaphase when the flow reverses direction. Together with the previously characterized role of anaphase flows in specifying daughter cell size asymmetry, our results indicate that multiple phases of cortical actomyosin dynamics regulate asymmetric cell division.

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与神经母细胞极性循环耦合的皮质肌动球蛋白动力学阶段

Par 复合体动态极化到不对称分裂的果蝇的顶端皮层神经母细胞在那里指导命运决定因素的分离。以前我们表明，极化 Par 复合体的顶端定向皮层运动需要 F-肌动蛋白（Oon 和 Prehoda，2019 年）。在这里，我们报告了皮质肌动球蛋白动力学的发现，当 Par 复合物在细胞质中时，它在间期开始，但最终与皮质 Par 动力学紧密耦合。间期皮质肌动球蛋白动力学是无方向的和脉动的，但当 Par 蛋白 aPKC 在皮质上积累时，在早期有丝分裂中迅速变得持续和顶端定向。顶端肌动球蛋白流驱动 aPKC 合并成一个顶端帽，当流动反向时，顶端帽在后期去极化。连同之前表征的后期流动在指定子细胞大小不对称方面的作用，