Newly established ectopic cell–cell contact acts as a symmetry-breaking cue to recruit WAVE and Arp2/3. (A) Micrographs from time-lapse movies of chimeric embryos created by combining two embryos expressing WAVE and Arp2/3. The DIC channel of the whole chimera is shown on the left, and two fluorescence channels of a blow-up of the chimeric contact (outlined region) are shown on the right. Yellow arrows point to ectopic cell–cell contacts. (B) Violin plots reporting normalized fluorescence intensity of WAVE and Arp2/3 at ectopic/endogenous cell–cell contacts and the contact-free cell apex (center dot, mean; vertical line, s.d.; outline, the distribution of the data; n = 15 chimeras). Statistical tests for experiments in B were chosen based on the normality and variance of the data: For WAVE, Kruskal–Wallis test followed by post-hoc Dunn’s test; for Arp2/3, one-way ANOVA followed by post-hoc Tukey’s tests. **P < 0.01, ***P < 0.001, ****P < 0.0001. Scale bar: 5 µm.