Treatment with CK666 inhibits Arp2/3-mediated branched actin network formation, leading to reduced lamellipodial protrusions and impaired cell polarization. This figure compares untreated HaCaT cells (control) with cells treated with 1% DMSO (vehicle control) and increasing concentrations of CK666 (from 25 μM to 100 μM). Violin plots show the angular probability distribution (φ+) of +1/2 defect orientation during near-annihilation events. The root-mean-square velocity (VRMS, mean ± standard deviation; shown on the right blue axis) decreases sharply. Despite the strong reduction in collective cell motion, the bimodal distribution of φ+ remains consistent across all treatment groups, in agreement with the results presented in Extended Data Fig. 3. HaCaT cells were generously provided by Joseph Kost (Ben-Gurion University of the Negev). The data represent measurements from n = 3 independent biological replicates, each collected over a 20-hour period following cell confluence. Upon reaching confluence, the growth medium was replaced with fresh medium containing CK666 (Sigma-Aldrich, SML0006) at concentrations ranging from 0 μM to 100 μM, prepared in growth medium supplemented with 1% DMSO. The 0 μM condition served as the vehicle control and contained 1% DMSO without CK666. (a) Distance between ± 1/2 defect pairs as a function of time after creation (blue)...