Asymmetry in the frequency and position of mitosis in the mouse embryo epiblast at gastrulation

A

Representation of the position of the AVE (yellow), AVE‐opposed area (green) and the AVE‐adjacent area (pink) in WT (left) and Rac1 ^KO (right) embryos.

B, C

3D reconstruction (B) and confocal Z‐slice (C) of E6.5 WT (left) and Rac1 ^KO (right) embryos stained for an AVE marker (Cerberus, yellow), F‐actin (Phalloidin, grey) and mitosis (Phh3, magenta). Scale bar: 25 μm. Blue dotted line delimitates the pro‐amniotic cavity (apical side of the epiblast). Red arrowheads point to non‐apical mitosis. White lines delimitate the boundary between extraembryonic (up) and embryonic (down) regions of the embryo.

D

Percentage of AVE migration in WT and Rac1 ^KO mutants. Data information: Mean ± SEM. WT: n = 38 embryos; Rac1 ^KO: n = 7 embryos. Normality was assessed using a Shapiro–Wilk test followed by Mann–Whitney test. ***P‐value ≤ 0.001.

E

Ratio of non‐apical mitosis (non‐apical Phh3 over total Phh3, normalized by the volume expressed in μm³) in percentage in WT and Rac1 ^KO mutants in AVE‐adjacent compared with AVE‐opposed regions. Data information: Mean ± SEM. WT: n = 38 embryos; Rac1 ^KO: n = 7 embryos. Normality was assessed using a Shapiro–Wilk test followed by Mann–Whitney tests. **P‐value ≤ 0.01 and ***P‐value ≤ 0.001.

Figure EV5. Non‐apical mitosis is a feature associated with the PS .