Resonant microchannel volume and mass measurements show that suspended cells swell during mitosis

Abstract

Suspended cells transiently increase their volume during mitosis because of ion exchange through the plasma membrane.

Coupling changes in cell shape to chromosome segregation

“…Simultaneously, the mixing of cytoplasm and nucleoplasm induced by the loss of the nuclear compartment is likely to induce a sudden drop in the concentration of proteins localized to only one of the two compartments -inducing profound changes in cellular biochemistry and cytoarchitecture. This is augmented by osmotic swelling 59 and a sudden influx of water, leading to a significant (>10%) increase in cell volume that is independent of the actin cytoskeleton 60,61 and a dramatic increase in cell height 59,62,63 . In combin ation, changes in cell architecture, actin remodelling, cell-substrate adhesion and osmotic swelling, cause cells to assume a spherical shape by the time they have assembled a metaphase plate (FIGS 1,3a).…”

“…In fact, entry into mitosis is accompanied by a rapid, nearly tenfold decrease in cell compliance (equivalent to an increase in cell stiffness). This is dependent on both osmotic swelling, which can be inhibited by the Na + /H + antiporter poison (EIPA) 59,60 , and the cortical actomyosin network 13,52 . These forces are sufficient to deform neighbouring cells within a crowded epithelial tissue 11,66 (FIG.…”

Weak protein–protein interactions in live cells are quantified by cell-volume modulation

“…In fact, the sensitivity of weak complex populations to cellular volume changes suggests a class of protein complexes whose association strongly depends on cellular crowding conditions. Such complexes imbue the cell with the ability to detect, signal, and/or directly initiate regulatory processes quickly and effectively in response to external stresses or internal signals, such as the rapid volume increase that occurs upon entry to mitosis (20,23).…”

“…Our model predicts that this sensitivity is particularly high when the dissociation constant K d is of the order of the protein's cellular concentration. It is known that the cell changes its volume as part of an internal regulatory process, or in response to environmental duress (20,23). We propose that such cellular volume change can trigger regulatory responses rapidly and reversibly, purely by altering the concentrations of complexed proteins, an effect that is amplified because the free volume (the volume that is occupied by water and other small, permeable solutes) in the cell is less than the overall cellular volume.…”

“…Volume change is a mild perturbation that happens routinely: Cells change their volume by up to 30% in both routine cell-cycle changes and in response to deleterious conditions (19)(20)(21). Rapid volume changes (approximately 1-100 s) are driven by water influx or efflux, altering the concentration of all molecular species contained within the cellular matrix (19,22,23). At such short times, regulatory actions taken by the cell to cope with the change in volume, such as synthesizing channels, chaperones, and enzymes are scarcely initiated (24,25).…”