Fig. 2. Experiment A (see Fig. 1C). One day after APH excision (E2.5), (A) a fragment of notochord or (B) SHH-producing cells were grafted between the neural tube deprived of midline cells and the paraxial mesoderm over a length of several somites. (F,J) Dorsal views, at E3.5, of embryos grafted respectively with a notochord or SHH-producing cells. Consecutive sections, at the levels indicated, either in the notochord-grafted region (C-E), or in the non-grafted region of the same embryo (G-I), or in the region grafted with SHH-producing cells (K-M), were hybridized with Shh (C,G,K) or Pax3 (D,H,L) probes or examined for apoptosis using TUNEL (arrowheads) (E,I,M). En, endoderm; No, notochord; NT, neural tube; Shh, SHH-producing cells; So, somite.
