Late in cortex reassembly, myosin (green) is recruited to foci at bleb membranes (red).

On page 477, blebbing cells open a window into the formation of a contractile actin cortex. Charras et al. use the blebs to order the events of cortex assembly.

Blebs form (usually during apoptosis or cytokinesis) as a result of strong actomyosin forces that separate a section of the plasma membrane from its underlying cortex and inflate it with cytosol. This free membrane is then a platform for new cortex assembly, which the authors watched by tracking potentially relevant proteins.

Cortex assembly occurred via three independent steps. First, ezrin and moesin—proteins that establish links between the membrane and cytoskeleton—were recruited to the blebs.

Actin polymerization and the membrane recruitment of several actin-binding proteins followed. The authors suspect that new actin is nucleated by a formin, based on filament morphology and...

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