Fig. 2: Emergence of a nematic phase during Xenopus CE.

a, b Snapshots of Xenopus laevis tissue at different timepoints. c Time dependent changes in the shape index SI(t) of the notochord cells in the field of view. The orange and red lines are linear fits (SI(t) = 4.7 × 10⁻⁴t + 1.59, 6.1 × 10⁻⁴t + 1.6) with open circles (mean values). The data at early and late timepoints are separated by a jump (blue dashed line, see also the inset for the derivative of SI(t)) in SI(t) at t = 70 min. The open circles give the mean SI values of all cells in the field of view at each time point. The shaded area shows the SEM. n ≈ 200 cells from Supplementary Movie IV. d Cell orientation in Xenopus tissues early during CE. The short lines are color coded by the value of |\(\theta\)| (defined in Fig. 1d). e, f Nematic order parameter, S, as a function of the cell position along anteroposterior or mediolateral axis at an early timepoint. The two curves are obtained by averaging over 30 successive time frames spanning one hour. g–i Same as (d–f), except later. j Temporal evolution of the nematic order parameter S of cells in the field of view. The solid line is a power-law fit (functions listed in the figure) with circles (mean values). The shaded area shows the SEM. The inset shows the SI(t) and S(t) in the same plot. k Spatial correlation, S, of notochord cells at different times. Solid lines are a power-law fits (functions listed in the figure) of the data at different times. l (I–VIII) Same as Fig.1l, showing the propagation of the nematic order (see the black region enclosed by the white dotted line). Each figure in (I–VIII) is averaged over three successive time frames (2-min interval). The scale bar in (a), (b), and (l) is 50 μm.