Inhibition of polar actin assembly by astral microtubules is required for cytokinesis

During cytokinesis, the actin cytoskeleton is partitioned into two spatially distinct actin isoform specific networks: a beta -actin network that generates the equatorial contractile ring, and a gamma -actin network that localizes to the cell cortex. Here we demonstrate that the opposing regulation of the beta- and gamma -actin networks is required for successful cytokinesis. While activation of the formin DIAPH3 at the cytokinetic furrow underlies beta -actin filament production, we show that the gamma -actin network is specifically depleted at the cell poles through the localized deactivation of the formin DIAPH1. During anaphase, CLIP170 is delivered by astral microtubules and displaces IQGAP1 from DIAPH1, leading to formin autoinhibition, a decrease in cortical stiffness and localized membrane blebbing. The contemporaneous production of a beta -actin contractile ring at the cell equator and loss of gamma -actin from the poles is required to generate a stable cytokinetic furrow and for the completion of cell division. During cell division, the actin cytoskeletal network at both the equatorial contractile ring and cell cortex are known to play a role, but the regulation of gamma -actin during cytokinesis is less well understood. Here, the authors show that recruitment of beta -actin to the contractile ring and loss of gamma -actin from the cell poles is required for completion of cell division.

Automated summary

During cell division, the opposing regulation of beta-actin and gamma-actin networks is crucial for successful cytokinesis. Depletion of gamma-actin at cell poles through localized deactivation of DIAPH1, and production of a beta-actin contractile ring at the cell equator, are necessary for the completion of cell division.