Fig. 3

Cell proliferation profiles and architecture of the trunk neuroectoderm. a, b, c, d Apotome images of larval trunk neuroectoderm showing patterns of cell proliferation following static 30-min EdU (green) pulses and nuclear stain (magenta). Bottom two rows (a.1, a.2, b.1, b.2, c.1, c.2, d.1, d.2) show orthogonal projections of the trunk neuroectoderm through anterior and posterior segment groups along the yellow dashed lines in a, b, c, d labeled 1 and 2. Closed arrowheads in a-d.2 indicate surface EdU⁺ cells while open arrowheads indicate subsurface EdU⁺ cells within the boundaries of the presumptive neuroectoderm. e–g Graphs indicating comparative cell proliferation profiles between segments of the trunk across stages 4–6. The capital letters on top of the boxplots (e.g. A, B etc.) indicate statistical significance for comparison of individual segment groups (ROIs) across stages based on our mixed effects model analysis. The upper and lower bounds of the box plot indicate the 3rd and 1st quartiles while the middle line inside the boxplot indicates the median. The ends of the whiskers represent the 5th and 95th percentiles, dots represent outliers. h–j 45-min static EdU labeling coupled with PH3 immunostaining across stage 4 till stage 6. h', h", i', i", j' and j" represent orthogonal views of the trunk neuroectoderm through anterior (h', i', j') and posterior regions h", i", j" of the trunk. Closed arrowheads indicate PH3+ cells adjacent to another PH3+ cell or EdU⁺ cell. Open arrowheads indicate subsurface PH3+ cells in the trunk. In panels a, b, c, d, h, i, j, anterior is to the left and posterior to the right. The stage investigated is indicated on the upper right-hand corner, while the orientation of the animal is indicated on the lower right corner. Dashed circles in c, c.1, d, d.2 indicate presence and loss of EdU⁺ cells from segments 2–4. In orthogonal views (a.1, a.2, b.1, b.2, c.1, c.2, c.1, d.2, h′, h″, i′, i″,j’, j″), apical is up and basal is down and the yellow dot denotes the ventral midline. ST3mo: Stage 3 mouth, ST4pt: Stage 4 prototroch, ST4tt: Stage 4 telotroch. Vent, ventral, Asterisk indicates the mouth. Scale bar: 50 μm