Mechanical control of mitotic progression in single animal cells

Abstract

Despite the importance of mitotic cell rounding in tissue development and cell proliferation, there remains a paucity of approaches to investigate the mechanical robustness of cell rounding. Here we introduce ion beam-sculpted microcantilevers that enable precise force-feedback-controlled confinement of single cells while characterizing their progression through mitosis. We identify three force regimes according to the cell response: small forces (∼5 nN) that accelerate mitotic progression, intermediate forces where cells resist confinement (50-100 nN), and yield forces (>100 nN) where a significant decline in cell height impinges on microtubule spindle function, thereby inhibiting mitotic progression. Yield forces are coincident with a nonlinear drop in cell height potentiated by persistent blebbing and loss of cortical F-actin homogeneity. Our results suggest that a buildup of actomyosin-dependent cortical tension and intracellular pressure precedes mechanical failure, or herniation, of the cell cortex at the yield force. Thus, we reveal how the mechanical properties of mitotic cells and their response to external forces are linked to mitotic progression under conditions of mechanical confinement.

Coupling changes in cell shape to chromosome segregation

“…The precise mechanisms underlying spindle-cortex crosstalk remains an interesting and unsolved problem. In addition, little is known about the mechanisms that are used to ensure that mitosis and cell division are mechani cally robust 62 and that the various organelles are precisely segregated during division [142][143][144] , or about the mech anisms that are used to bias these processes to achieve the same precision during asymmetric divisions. Finally, very little is known about the evolution of eukary otic cell division, which appears to have its origins in Archaea 2,145 .…”

“…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).…”

Autophagic flux is highly active in early mitosis and differentially regulated throughout the cell cycle

“…However, it is highly dynamic that includes prophase, prometaphase, metaphase, anaphase, telophase and cytokinesis. All these dynamic events need to be finished in 1–2 hours, which is a high energy demanding process and involves lots of cellular remodeling [1–4]. …”

Atomic Force Microscopy in Characterizing Cell Mechanics for Biomedical Applications: A Review

“…Actins are stained as green fluorescence. (C, D) Measuring the force generated by single cell during mitosis by AFM [148], [149]. (C) Schematic diagram of measuring the generated forces at different stages of mitosis with wedged parallel cantilever [149].…”

“…The force exerted by the rounding mitotic cell was sensed by the AFM cantilever and recorded over time [148]. The regular AFM cantilever has a tilt degree (∼10°) [149], which often results in that cells easily slide away from the cantilever when placing AFM cantilever on cells. In order to eliminate this effect, a wedge was combined with the AFM cantilever to compensate the tilt for parallel probing force of cell rounding [150].…”