Figure 4. Three-dimensional tracking of all epiblast nuclei in a region of the epiblast.

(A) Kymographs of apical and basal migrations. The positions of each nucleus were reconstructed in Movies S4 (distal view) and S5 (lateral view). (B) Nuclear density compared among three sections along apical–basal axis (n = 18). (C) The correlation between velocity and the difference between the distances of a nucleus from its forward and backward neighbors. If migrations were caused by pushing forces from neighboring nuclei, the velocity should become grater when the difference in distances increases. However, velocity in neither direction was correlated with the difference in distance (apical, R² = 0.0232; basal, R² = 0.0011).