Fig. 2
The presumptive neuroectoderm of the VNC is derived from sub-clones of the 2d112 blastomere. (a–f′) Apotome images of DiI injected animals from stages 3–6 shown in ventral view. Top rows (a, b, c, d, e, f) show merged channels for nuclear stain (cyan) and DiI (red) while bottom row (a′, b′, c′, d′, e′ f′) indicates only DiI labeling in black and white. Panels a–e’ are superficial, panels f and f' indicate a subsurface projection showing VNC ganglia. In panels f and f', DiI labeling in the neurites is brighter than other tissues as labeling in the cell bodies become patchier after fixation. (g–l) Orthogonal sections through the anterior half of the ventral trunk neuroectoderm showing apical (up) and basal (down) boundaries of DiI labeled patches (red) and nuclear stain (cyan). Panel l highlights an orthogonal view of a 2d1 injected embryo grown for 120 hpi (stage 6 late) showing neurotroch (nt) on the surface and VNC subsurface. (m, n) Ventral views of DiI injected animals at 48 hpi (stage 4) with cell outlines marked with F-actin (white) for a 2d112 injected animal m and a 2d2 injected animal n. Arrows in m and n indicate F-actin bundles showing apical constriction. Closed arrowheads in panel n shows a DiI+ cell intercalated with DiI− cells denoted by open arrowheads. o Diagram showing the different tissues contributed by each of the 2d daughters at different developmental stages encompassing neurogenesis. The length of time grown is indicated as hours post-injection (hpi) on the lower left corner of each figure panel. Asterix denotes the position of the mouth. In panels a–f′, the number of animals evaluated at each stage after injection is shown at the upper right corner. The corresponding stages of each animal is indicated on the upper right corner of the lower panels a’–f′. In all orthogonal views g–l, apical is up and basal is down and the yellow dot shows the position of the ventral midline. Orange dashed line indicated the leading edge of the DiI+ trunk neuroectoderm. Prototroch (pt) and telotroch (tt) are indicated by dashes. bp: blastopore, nt: neurotroch, ntL: left neurotroch, ntR: right neurotroch, mo: mouth, sc: sensory cell, nec: neuroectoderm, vnc: ventral nerve cord, pt.: prototroch, ptL: left prototroch, ptR: right prototroch tt: telotroch, ttL: left telotroch, ttR: right telotroch, pg: pygidium, pgL: left pygidium, pgR: right pygidium, ST3bp: Stage 3 blastopore, ST3mo: Stage 3 mouth, ST6l: Stage 6 late. Scale bar: 50 μm