LAUSR

Cell polarity is facilitated by a rearrangement of the actin cytoskeleton at the cell cortex. The program triggering the asymmetric remodeling of contractile actomyosin networks remains poorly understood. Here, we show that polarization of Caenorhabditis elegans zygotes is established through sequential downregulation of cortical actomyosin networks by the mitotic kinase, Aurora-A. Aurora-A accumulates around centrosomes to locally disrupt the actomyosin contractile activity at the proximal cortex, thereby promoting cortical flows during symmetry breaking. Aurora-A later mediates global disassembly of cortical actomyosin networks, which facilitates the initial polarization through suppression of centrosome-independent cortical flows. Translocation of Aurora-A from the cytoplasm to the cortex is sufficient to interfere with the cortical actomyosin networks independently of its roles in centrosome maturation and cell-cycle progression. We propose that Aurora-A activity serves as a centrosome-mediated cue that breaks symmetry in actomyosin contractile activity, and facilitates the initial polarization through global suppression of cortical actomyosin networks.