Pinching the cortex of live cells reveals thickness instabilities caused by myosin II motors

The cell cortex is a contractile actin meshwork, which determines cell shape and is essential for cell mechanics, migration, and division. Because its thickness is below optical resolution, there is a tendency to consider the cortex as a thin uniform two-dimensional layer. Using two mutually attracted magnetic beads, one inside the cell and the other in the extracellular medium, we pinch the cortex of dendritic cells and provide an accurate and time-resolved measure of its thickness. Our observations draw a new picture of the cell cortex as a highly dynamic layer, harboring large fluctuations in its third dimension because of actomyosin contractility. We propose that the cortex dynamics might be responsible for the fast shape-changing capacity of highly contractile cells that use amoeboid-like migration.

Automated summary

The cell cortex is a contractile actin meshwork that determines cell shape and is essential for cell mechanics, migration, and division. The thickness of the cortex fluctuates in the third dimension due to actomyosin contractility, leading to a highly dynamic layer. This dynamic nature of the cortex may be responsible for the fast shape-changing capacity of highly contractile cells using amoeboid-like migration.