Shape is Coupled with Active Motion in Cell Aggregates

Cell motion involves active processes where energy in the form of ATP is expended to drive motility. In eukaryotic cells, this motion is mediated by the actin-myosin complex, which acts on the cell cytoskeleton to induce motility. The forces that allow cells to move also cause changes in their shape. In isolation, cell shape can be highly fluctuating. However, when cells form confluent aggregates, we find that the cell shape distributions take on distinct forms for static versus mobile aggregates. For example, we find that the distribution of shape parameters P(A) (ratio of the perimeter squared to 4 times the area) for confluent monolayers of motile MDCK cells is a Gamma distribution with an average shape parameter Ā~1.34. To investigate the mechanisms that control to the shape parameter distribution, we carried out deformable particle model simulations with energetic terms that penalize deviations in cell volume and bending of the cell surface, as well as active Brownian forces with magnitude f₀ and persistence time t_p that generate cell motion. For each persistence time t₀, we find a characteristic active force above which the aggregates are fluid-like with significant cell motion and below which the aggregates are static. For all f₀< f₀*, the shape parameter distribution is a Gamma function with average shape parameter Ā~1.15, whereas for liquid-like systems with f₀< f₀*, the distribution broadens with Ā~1.34.

We acknowledge funding from the NIH Training Grant Award Number 1T32GM145452