Quantification of Brillouin shift averaged over 18 cells engaged in apical constriction and invagination during VFF progression, as inferred from SPIM slices (dashed box in c ). Changes in Brillouin shift are shown relative to the Brillouin shift at timepoint 0 min, which corresponds to the initiation of apical constriction. Data points are average Brillouin shift in the contractile domain, error bars denote s.d. over different slices of each analyzed embryo. Statistical significance was evaluated using a paired one-way ANOVA test (F = 44.29, P = 0.066), followed by a post-hoc multiple comparison test (false discovery rate corrected, α = 0.05, q-value = 0.1); * P = 0.039, ** P = 0.0054 ( n = 3 embryos from independent experiments).
