Fig. 7. Hox identity is not determined in tail bud progenitor cells. (A) Tail bud (stage 15 HH) hybridised for Hoxa10. (A') Mid-sagittal section (stage 16 HH) immunostained for Hoxc10. Arrow indicates the CNH. (B-D') CNH or dpTB regions (stage 15 HH) grafted into stage 8 HH hosts. In situ hybridisations were carried out for Hoxa10. (B,B') One hour incubation. GFP⁺ tissue expresses Hoxa10. Eight-(C,C') or 48 (D,D')-hour incubations. Anterior GFP⁺ tissue is negative for Hoxa10. (E,E') Anterior transverse section from a similarly grafted embryo after 48 hours, immunostained for Hoxc10. Arrows indicate Hoxc10 positive GFP⁺ cells. (F-J') Whole-mount (F) and transverse sections (F'-J') of an embryo grafted as in B-D and incubated for four days (stage 25 HH). Transverse sections at the level of the anterior arrow were immunostained for Hoxc8 (F'-H'), and those at the level of the posterior arrow with a Hoxc10 antibody (I-J'). Anterior sections from embryos after (G,G') a homotopic caudal node graft or (H,H') a heterochronic CNH graft, immunostained for Hoxc8. Arrows indicate Hoxc8-positive GFP⁺ cells; asterisks indicate Hoxc8-positive host cells. Posterior sections after (I,I') a homotopic caudal node graft or (J,J') a heterochronic CNH graft, immunostained for Hoxc10. Arrows indicate Hoxc10-positive GFP⁺ cells. Blue, nuclear stain. Scale bars: A,B,B'-D', 0.5 mm; A', 0.1 mm; F', 250 µm; E,E',G-I', 30 µm.