During mitosis, adherent cells change from a flattened to a rounded morphology, and this is thought to be necessary for the geometric requirements of cell division. Here, the forces that drive this shape change are studied. Mitotic rounding force depends both on the actomyosin cytoskeleton and the cell's ability to regulate osmolarity. The rounding force is generated by osmotic pressure and the actomyosin cortex maintains this rounding pressure against external forces. These results support the idea that in animal cells, the actomyosin cortex behaves like an internal cell wall that directs osmotic expansion to control cell shape.
- Martin P. Stewart
- Jonne Helenius
- Anthony A. Hyman
