Fig. 5. After only neural tube removal, En1 but not Wnt11 is activated at the level of the presomitic mesoderm (PSM). (A) The neural tube (nt) was removed from somite X to the PSM (between the arrows) leaving the notochord (nc) in place. Embryos were fixed after 48 hours (in B, the bracket indicates a region where a ventral part of neural tube was accidentally left in place). Dorsal views and corresponding transverse sections of embryos hybridized with Wnt11 (B-D) or En1 (E-G) probes. (B,C,E,F) At the anterior level, where somites were already segmented, Wnt11 (B,C) and En1 (E,F) are expressed in distinct domains of the mesenchyme. (B,D,E,G) At the posterior level, where somites were still unsegmented, Wnt11 is not activated (B,D), in contrast to En1, the expression domains of which are fused in a single medial band (E,G). ec, ectoderm; dml, dorsomedial lip. Scale bars: 50 µm.