Apoptotic regulators dispose of the midbody

A pathway that clears up the remains of dead cells also removes the debris generated during cell division, Chai et al. report.

The midbody is a microtubule-rich structure that connects the two daughter cells at the end of mitosis. When cytokinesis is completed, the midbody is either shed into the extracellular space or retained by one of the daughter cells, potentially influencing its developmental fate. Chai et al. found that, in C. elegans, asymmetrically dividing Q neuroblasts discard their midbodies into their surroundings.

The Q cell midbodies were subsequently engulfed and degraded by a neighboring epithelial cell called hyp7, which also internalizes the corpses of apoptotic Q cells during development. Mutations in the genes that promote apoptotic cell engulfment blocked midbody clearance, indicating that hyp7 cells use the same pathway to internalize Q cell corpses and cytokinetic midbodies. Indeed, Chai et al. found that, just like apoptotic cells, Q cell midbodies expose phosphatidylserine on their outer surface and that blocking this lipid signal prevented the hyp7 cell from recognizing and engulfing the remnants of Q cell divisions.

Apoptotic engulfment genes also regulated midbody clearance in other C. elegans cell lineages. But senior author Guangshuo Ou now wants to study the function of the midbodies produced by worm epithelial stem cells, which are specifically retained by the daughter cell that remains undifferentiated.