TY - JOUR TI - Cytokinesis in vertebrate cells initiates by contraction of an equatorial actomyosin network composed of randomly oriented filaments AU - Spira, Felix AU - Cuylen-Haering, Sara AU - Mehta, Shalin AU - Samwer, Matthias AU - Reversat, Anne AU - Verma, Amitabh AU - Oldenbourg, Rudolf AU - Sixt, Michael AU - Gerlich, Daniel W A2 - Balasubramanian, Mohan K VL - 6 PY - 2017 DA - 2017/11/06 SP - e30867 C1 - eLife 2017;6:e30867 DO - 10.7554/eLife.30867 UR - https://doi.org/10.7554/eLife.30867 AB - The actomyosin ring generates force to ingress the cytokinetic cleavage furrow in animal cells, yet its filament organization and the mechanism of contractility is not well understood. We quantified actin filament order in human cells using fluorescence polarization microscopy and found that cleavage furrow ingression initiates by contraction of an equatorial actin network with randomly oriented filaments. The network subsequently gradually reoriented actin filaments along the cell equator. This strictly depended on myosin II activity, suggesting local network reorganization by mechanical forces. Cortical laser microsurgery revealed that during cytokinesis progression, mechanical tension increased substantially along the direction of the cell equator, while the network contracted laterally along the pole-to-pole axis without a detectable increase in tension. Our data suggest that an asymmetric increase in cortical tension promotes filament reorientation along the cytokinetic cleavage furrow, which might have implications for diverse other biological processes involving actomyosin rings. KW - cytokinesis KW - actomyosin ring KW - cell division KW - actin KW - fluorescence polarization microscopy KW - cell cortex JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -