LAUSR

Cytokinesis is driven by a contractile ring whose key components are well-defined. Yet how they are organized and how the contractile ring assembles and constricts, remain unclear. This study combines confocal and super resolution imaging of endogenous contractile ring components in sea urchin embryos ( in vivo) and isolated embryo cortices ( ex vivo), to demonstrate that anillin and septin2 assemble into myosin II-positive clusters. The authors surmise that these clusters are precursors to the contractile ring and observe septin filament nanostructure for the first time in an animal cell contractile ring. These insights into the organization of lesser studied yet conserved contractile ring proteins, anillin and septins, provide clues to their function and pave the way for similar studies in other animal species.