Fig. 3. Hoxd10 expression in whole-mount embryos after reversals of neural tube segments at the T-LS boundary. (Left) Schematics of stage 13 and 15 embryos. Anterior CNS regions are shown in blue; prospective LS regions, in yellow. The boxed areas in the drawings of normal whole embryos correspond to the expanded diagrams showing reversal surgeries. (A-D) Ventral views of posterior spinal cord regions from control (A) and experimental embryos (B-D) at stages 27-34. Transplant regions are delineated by brackets in this and all subsequent figures. Following reversals of either T6-LS3 (B) or T6-LS2 (C) at stage 15, the manipulated segments show a reversal of the normal Hoxd10 expression pattern. The spinal cord shown in C exhibits lower Hoxd10 expression in the LMC (arrow) than that shown in B, in accord with its older stage of sacrifice (B, stage 27; C, stage 34). Following reversals of T6-LS2 at stage 13, Hoxd10 expression is low in both reversed T and LS segments at stage 29. Only the originally posterior-most segment in the reversal region (the original LS2) shows Hoxd10 expression above that found in a normal mid-T segment. st, stage. Bars, 250 µm.