Fig. 4. Tissue movements during both WT and Tc-zen1^RNAi DC include early pulsatile progression and flank spreading, followed by a global anteriorward shift.

(A–B) WT, (C–E) Tc-zen1^RNAi. (A,C) Representative images from nuclear tracking analyses, with color-coding for tissue type as indicated (see also supplementary material Movies 3, 4, 6, 8). Images are stage-matched for EE area, meaning that only the later, faster phase is shown for Tc-zen1^RNAi DC. For clarity, Tc-zen1^RNAi amniotic tracks are omitted in C2 (but shown in supplementary material Movie 8, as are anterior nuclei that could only be followed prior to anterior bulge resorption). Shorter tracks for three individual Tc-zen1^RNAi epidermal cells are due to a small, external visual obstruction. (B,D) Higher magnification of selected tracks (5.2-hour duration, earlier start time in D than in C1) that are marked with white circles in A,C, respectively. The initial zigzag track shape shows the undulating waves of DC phase I, which is more pronounced in WT. (E) Labeling of the left flank from C3, illustrating the changing epidermal cell trajectories (15.5-hour interval, starting 6.8 hours before C1): vertical dashed line demarcates anterior from posterior halves, as determined by spreading of the flanks over the egg equator; horizontal dashed line demarcates early (lower) and later (upper) track segments at the point when the anteriorward postural shift begins. This also occurs in WT (A3). Views are dorsal, with anterior left. Abbreviations as in previous figures. Scale bars: 100 µm (A1–A3,C1–C3), 20 µm (shown in D for B,D), 50 µm (E).