Fig. 1. Neural plate hinge cells contain heterogeneous apical domains.

a, b’ Dorsal view of the middle area of a control Xenopus neural plate stained with phalloidin (a) and the segmented image (a’) at stage 15. The rectangular area in (a), corresponding to the medial hinge, is enlarged in (b). b Cells with small apical domain (red) are interspersed with large cells elongated along the AP axis (green bars). c Rose plots show the orientation of the cells relative to the anteroposterior (AP) axis. n = 929 cells. Data from three stage 15 embryos are combined. d In the dorsolateral hinge region, cells with small apical domain (red) are adjacent to elongated cells (blue). Neuroepithelium (NE) and non-neural ectoderm (N-NE) are in the upper and lower parts of images, respectively. The histogram of apical domain size (e) and cell aspect ratios (f) of cells in stage 11 embryonic ectoderm (green), and cells in the medial or dorsolateral hinge (blue) and non-hinge (red) areas of stage 15 neural plate. Four-to-five rows of cells at the dorsal midline were considered the medial hinge area. The non-hinge areas exclude four-to-five rows of cells from the medial and dorsolateral hinges. Data (means ± s.d.) are combined for three stage 15 embryos and four 11 stage embryos, representative of three independent experiments. Stage 15 hinge, n = 255 cells; stage 15 non-hinge, n = 426 cells; stage 11 ectoderm, n = 1218 cells. The experiments were repeated at least three times. Coefficients of variation (CV) are shown in Supplementary Table 1. One-way ANOVA Kruskal-Wallis test. One-sided. p < 0.0000000001 (e). p < 0.0000000001 (f). Scale bars are 50 μm in (a, a’), 20 μm in (b) and (d).