Extended Data Fig. 3: Cell sorting involves active directed migration of PrE cells towards the surface via actin-mediated protrusions.
From: Coupling of cell shape, matrix and tissue dynamics ensures embryonic patterning robustness
a. Representative time-lapse images of mosaic-labelled blastocysts at E3.5 and E4.5 generated to visualize EPI and PrE cell dynamics. b. Probability of EPI and PrE cells to move towards the cavity surface as a function of cellular distance from the lumen, plotted as mean±SD. Probabilities are estimated from single-cell tracking in mosaic-labelled blastocysts from Fig. 2b, c n = 14 EPI cells, 31 PrE cells from 13 embryos. For details, see Methods. c. Polar histogram for protrusion angles sampled from a uniform distribution between 0-180 degrees. d. Distribution of protrusion length in PrE cells as measured from centre of the nucleus to tip of the longest protrusion. Mean protrusion length = 13.38 ± 3.12 µm. n = 113 measurements, 43 cells from 12 embryos. e. Quantification of total number of ICM cells in control and latrunculin B-treated ICMs. n = 20,11 ICMs for the two groups, respectively. Two-sided Mann–Whitney U-test, p = 0.207. f. Representative images of control E4.5 blastocysts and 100 µM and 200 µM NSC23766-treated E4.5 blastocysts and quantification of number of ectopic PrE cells in each condition. White arrowheads, ectopic PrE cells. n = 22, 8, 8 blastocysts for the treatment groups, respectively. Two-sided Mann–Whitney U-test, p = 0.011 for comparison between control and 100 µM group, p = 0.012 for comparison between control and 200 µM group. g. Quantification of total number of EPI and PrE cells in control and NSC23766-treated E4.5 blastocysts. n = 22, 8, 8 blastocysts respectively. Kruskal–Wallis test, p = 0.62 for EPI cell numbers, p = 0.903 for PrE cell numbers across the treatment groups. h. Quantification of total number of ICM cells in Rac1+/+, Rac1+/−, and Rac1−/− E4.5 blastocysts. n = 9, 17, 16 blastocysts respectively. One-way ANOVA, p = 0.826. Quantification of EPI/PrE cell fate proportion within the ICM in Rac1+/+, Rac1+/−, and Rac1−/− E4.5 blastocysts, plotted as mean±SD. One-way ANOVA, p = 0.216. Scale bar 20 μm. ns, non-significant, *p ≤ 0.05.
