Phys. Rev. Lett. 114, 208101 (2015)

Credit: © PHOTOTAKE INC. / ALAMY

Cells programmed to die undergo what's known as blebbing: the thin layer of crosslinked biopolymers underlying the membrane ruptures, causing it to bulge outwards in transient fluid-filled protrusions (pictured). These shape changes also occur during cell division and migration, and are generally thought to be driven by pressure-induced flow inside the cell — without radically modifying its volume. But now Alessandro Taloni and colleagues have observed fluid transport through the membrane of migrating stem cells, and found evidence to suggest that it facilitates blebbing.

The authors developed a way of imaging that allowed them to observe water flow in and out of the cells. They noted a marked reduction in bleb activity when this flow was hindered, and a correlation between surface and volume fluctuations. Together with simulations of fluid-mediated deformations, this led them to infer a link between blebbing and the fluctuations induced by water transport. Both experimental and numerical results seem to be incompatible with the oft-held assumption of conserved volume via an impermeable membrane — which may breathe new life into the study of cell death.