Fig. 2.

Quantitative 4D analyses of cells in the dorsal folds. (A) Basalmost initiating cells tracked into the anterior and posterior folds between 0 s and 800 s past the completion of cellularization. Colors designate the same cell between these two time points. (B) (Left) Example of smoothed traces of apical-basal length and volume for an individual cell. Gray points designate actual measurements. (Right) Boxplots of apical-basal cell length at the completion of cellularization (t=0 s) and at t=800 s for N=29 basalmost initiating cells. (C) The aspect ratio of basalmost initiating cells as measured manually using ImageJ from 2D z-stacks through the dorsal folds. (B,C) The ends of the boxes are the quartiles; the centerline is the median; and whiskers extend 1.5 times the interquartile range. (D) An example of a segmented cell (left) and its neighbors (middle). The contact surfaces of the cell (right) have been colored according to the colors of its neighbors. (E) (Left) Cell-cell contacts at the completion of cellularization (t=0 s) are indicated by edges in the graph. Nodes are positioned at projected cell centroids. Only cell-cell contacts between basalmost initiating cells and their first and second degree neighbors that were reliably tracked between t=0 s and t=800 s and that remained in the field of view were analyzed. Purple edges designate cell-cell contacts among these cells that decrease in surface area, and green edges designate cell-cell contacts that increase in surface area at 800 s. (Center and right) Smooth traces of cell contact surface area for the designated cell-cell contacts, as indicated by the colored squares in the left figure. Points correspond to actual surface area measurements. (F) Distribution of cell surface centroids relative to the projected cell centroid (center black point) at the completion of cellularization (t=0 s) for basalmost initiating cells and their first and second degree neighbors. Purple points designate the positions of contact surfaces that decrease in area at t=800 s past cellularization; green points designate the position of surfaces that increase in area at t=800 s relative to the focal cell. (G) Cells are labeled based on their neighbor relationship to the basalmost initiating cells (green). (H) Median distance of nuclei from the cell apices over time for the basalmost cells and their neighbors. Note that neighbors along the edge of the field of view were not analyzed.