Actomyosin-mediated cytoplasmic flows synchronize the cell cycle in <i>Drosophila</i> embryos

The synchronous cleavage divisions of early embryogenesis require coordination of the cell cycle oscillator, the dynamics of the cytoskeleton and the cytoplasm. As yet, it remains unclear how spatially restricted biochemical signals are integrated with physical properties of the embryo to generate collective cell cycle dynamics. Biochemical oscillations are initiated by local Cdk1 inactivation close to the nuclei and spread through the activity of mitotic phosphatase PP1 to generate cortical myosin II gradients. These gradients generate cortical and cytoplasmic flows that control proper nuclear positioning. Despite being in the very low Reynolds number regime, we find that Stokes flow does not adequately describe these flows. We will describe the physical properties of the flows, its role in nuclear migration and synchronization of the cell cycle in Drosophila embryos.