Patterned cell divisions require a precisely oriented spindle that segregates chromosomes and determines the cytokinetic plane. In this study, we investigated how the meiotic spindle orients through an obligatory rotation during meiotic division in mouse oocytes. We show that spindle rotation occurs at the completion of chromosome segregation, whereby the separated chromosome clusters each define a cortical actomyosin domain that produces cytoplasmic streaming, resulting in hydrodynamic forces on the spindle. These forces are initially balanced but become unbalanced to drive spindle rotation. This force imbalance is associated with spontaneous symmetry breaking in the distribution of the Arp2/3 complex and myosin-II on the cortex, brought about by feedback loops comprising Ran guanosine triphosphatase signaling, Arp2/3 complex activity, and myosin-II contractility. The torque produced by the unbalanced hydrodynamic forces, coupled with a pivot point at the spindle midzone cortical contract, constitutes a unique mechanical system for meiotic spindle rotation.

中文翻译：

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流体动力中的对称性破坏驱动哺乳动物卵母细胞的减数分裂纺锤体旋转。

图案化的细胞分裂需要精确定向的纺锤体，该纺锤体分离染色体并确定细胞动力学平面。在这项研究中，我们调查了在小鼠卵母细胞减数分裂过程中减数分裂纺锤体如何通过强制旋转定向。我们表明纺锤体旋转发生在染色体分离的完成，从而每个分离的染色体簇定义一个皮质的放线菌素域，产生胞质流，导致纺锤体上的流体动力。这些力最初是平衡的，但变得不平衡以驱动主轴旋转。这种力量失衡与皮质中Arp2 / 3复合物和肌球蛋白II的分布中的自发对称性断裂有关，这是由包含Ran鸟苷三磷酸酶信号传导，Arp2 / 3复合物活性，和肌球蛋白II的收缩力。由不平衡的流体动力产生的扭矩，加上纺锤体中间区域皮质收缩的枢轴点，构成了减数分裂纺锤体旋转的独特机械系统。