What can we learn from self-organization for the understanding of the spatio-temporal dynamics of the cytoskeleton

The response of the actin cytoskeleton to external chemical stimuli plays a fundamental role in numerous cellular functions. One of the key players that governs the dynamics of the actin network is the motor protein myosinII. Here we report on experiments and modeling on the interplay between myosinII and filamentous actin in Dictyostelium discoideum. In chemotactically compentent cells, upon uniform stimulation with the chemoattractant cAMP, myosinII is first released from the cortical region and then translocated back to the cortex with a time delay relative to the rapid increase of cortical actin. After the initial release of myosinII, the freshly formed filamentous actin pushed the membrane outward resulting in a change of cell morphology. By comparing with myosinII-null cells, we found that in the last stage of the cell response the coupling between myosinII and actin determines contraction dynamics. I shall also report on our approaches using phase field modeling.