Three-dimensional modeling and simulation of the cell cortex: bringing remodeling, elasticity and active forces together

The cell cortex is a thin layer of cross-linked actin filaments lying just beneath the plasma membrane of animal cells. The cell cortex plays a key role in biological processes involving mechanical and active forces, such as cytokinesis or migration. The structure of the cortex undergoes a turnover in about one minute, consisting in the rearrangement of the filament network. This rearrangement results from the polymerization and depolymerization of actin and the binding and unbinding of cross-linkers to the network. Due to the turnover, the cell cortex behaves as an elastic network at short time-scales but it resembles a viscous fluid at longer time-scales. Furthermore, the cortex is crowded with myosin motors, which generate a source of active tension. Here we bring together all these different ingredients in a three-dimensional and non-linear model of the cortex. We investigate the relevance of cortex viscoelasticity in processes such as cytokinesis or migration. Furthermore, we perform computer simulations of our model in different mechanical assays resembling experiments, which allow us to extract they key parameters of the model.