Membrane remodeling during embryonic abscission in Caenorhabditis elegans

Abscission is the final step of cytokinesis and results in the physical separation of two daughter cells. In this study, we conducted a time-resolved series of electron tomographic reconstructions to define the steps required for the first embryonic abscission in Caenorhabditis elegans. Our findings indicate that membrane scission occurs on both sides of the midbody ring with random order and that completion of the scission process requires actomyosin-driven membrane remodeling, but not microtubules. Moreover, continuous membrane removal predominates during the late stages of cytokinesis, mediated by both dynamin and the ESCRT (endosomal sorting complex required for transport) machinery. Surprisingly, in the absence of ESCRT function in C. elegans, cytokinetic abscission is delayed but can be completed, suggesting the existence of parallel membrane-reorganizing pathways that cooperatively enable the efficient severing of cytoplasmic connections between dividing daughter cells.