Fig. 3: Regional analysis of mechanical feedback coefficient and directionality.

A, A′ Trajectories of cells tracked for 20 min following head activation in dorsal (A) and ventrolateral (A′) regions ~50 um wide along the full AP axis. B Same regions as (A) and (A′) 10 min post activation (mpa) color coded for eccentricity. KS test returns the distributions of cell eccentricity are different, p = 7.5 × 10⁻⁴. B′ Same regions as (B) color coded for orientation of the cell long axis relative to the AP axis. KS test returns distributions of cell orientations are different, p = 5 × 10⁻¹⁹. C JMA in the dorsolateral region of the control (top) and activated (bottom) embryos at the same developmental stage. C′ JMA in the ventrolateral region of activated (top) and control (bottom) embryos at the same developmental stage. Regions in C, C′ are 30 um wide, spanning the full AP axis. B, C′ (See Fig. S1J). White dashed line shows the boundary of the activation region in the anterior. D Strain rate in junctions parallel to the AP axis in dorsal and ventral regions following head activation. N \(\ge\) 200 per region. E Myosin rate on junctions parallel to the AP axis in dorsal and ventral regions. Sample size as in D. D, E Red line indicates the median, box lower and upper quartiles, whiskers are minimum and maximum. F, F′ Strain rate vs myosin rate on junctions parallel to the AP axis in the dorsal (F) and ventral (F′) regions for all head activation experiments, N = 5 embryos. The Red line shows the best-fit proportionality of the data points. The legend shows the feedback coefficient and the 95% confidence interval. Error bars are SEM. G Comparison of feedback coefficient based on junction orientation (parallel to DV vs AP) and region (dorsal vs ventral). This coefficient is the proportionality between strain rate vs myosin rate plot as in (F, F′), Fig. S4G. H. P values are obtained by single-sided Welch t-test. N = 10. D–G Source data are provided as a Source Data file.