Spatial coordination of cytokinetic events by compartmentalization of the cell cortex.

During cytokinesis, furrow ingression and plasma membrane fission irreversibly separate daughter cells. How actomyosin ring assembly and contraction, vesicle fusion, and abscission are spatially coordinated was unknown. We found that during cytokinesis septin rings, located on both sides of the actomyosin ring, acted as barriers to compartmentalize the cortex around the cleavage site. Compartmentalization maintained diffusible cortical factors, such as the exocyst and the polarizome, to the site of cleavage. In turn, such factors were required for actomyosin ring function and membrane abscission. Thus, a specialized cortical compartment ensures the spatial coordination of cytokinetic events.