Figure 2: Mechanical induction of nuclear translocation of β-cat in the zebrafish embryo mesoderm.

(a) 4.8 hpf embryos at 30% epiboly. (b) 4.8 hpf embryos blocked at sphere after treatment with blebbistatin. (c) Blebbistatin-treated embryo compression and the resumption of epiboly movements and marginal cell dilation. (d) Blebbistatin washing and resumption of epiboly movements and marginal cell dilation. Deformations are assessed by PIV analysis. Note that velocity fields differ between c and d, but the dilations of the marginal cells in blue are the same. Scale bar, 100 μm (black and white bar). (e) β-cat labelling around the margin in dome to 5.7 hpf non-treated 50% epiboly embryos. (f) β-cat labelling around the margin in blebbistatin-treated embryos (nuclear in the dorsal pole only, see Supplementary Fig. S4a). (g) β-cat labelling around the margin after global deformation of blebbistatin-treated embryos. (h) β-cat labelling after blebbistatin washing upon resumption of endogenous movements. Scale bar, 20 μm (white bar). (i) Quantification of marginal β-cat-positive nuclei in controls (n=16), blebbistatin-treated (n=22), blebbistatin-treated and globally compressed (n=16), blebbistatin-treated and washed (n=10), and blebbistatin treated embryos with epiboly rescue by magnetic forces (n=17). Differences between control and blebbistatin-treated embryos, and between treated embryos and rescued embryos, are statistically significant according to Mann–Whitney’s exact test (P<0.001). Error bars are s.d. Note that ectopic positive nuclei in blebbistatin-treated and compressed individuals (Supplementary Fig. S5c) are not taken into account in this quantification.