Numerical simulations showing the impact of inter-filament cooperativity for the initiation of cofilin clusters on the fragmentation of twist-constrained two-filament bundles. Results of numerical simulations show that fragmentation of twist-constrained two-filament bundles (n = 50 simulated two-filament bundles) is faster with interfilament cooperativity for the initiation of cofilin clusters than without. Simulations with no interfilament cooperativity seem to better reflect the experimental observations (data from Fig. 6 C, n = 16 segments of two-filament bundles).