BPS2026 – Unveiling the mechanism of cortical actin flows during cytokinesis

Cytokinesis is the final step of cell division in which a parent cell is divided into two daughter cells. Large-scale cortical actin flows from poles to the cell equator have been observed before cytokinesis in animal cells. It has been suggested that the cortical flow contributes to the assembly of the contractile ring. It has been hypothesized that this cortical flow originates from the coordinated activities of actin filaments, cross-linking proteins, and myosin motors in the cell cortex. However, a detailed mechanism driving the cortical flow remains poorly understood. To unveil the mechanism, we employed an agent-based computational model for a two-dimensional actomyosin network with or without a cell membrane. Our simulations successfully reproduced the cortical flow and revealed that its emergence and dynamics are highly dependent on key molecular and structural parameters, including the densities of myosin motors and cross-linking proteins and the stiffness, orientation, and turnover of actin filaments. These results demonstrate how molecular-scale interactions between cytoskeletal proteins give rise to cell-scale flows. More broadly, our study provides new insights into understanding the physical principles of cytoskeleton remodeling and highlights the potential of agent-based models for bridging molecular mechanisms with emergent cell-scale behaviors.