Fig. 4. Dissection of pieces for grafting. (A) Ventral view of rostral node (RN), border (B) and streak 1 (St1) regions of an E8.5 embryo hybridised with a T (brachyury) in situ probe; (B,C) sagittal sections showing the same region in embryos hybridised with Foxa2 (B) or Fgf8 (C). Arrows delimit the regions dissected. (D-I) In situ hybridisation of dissected pieces. The rostral node expresses Foxa2 (D), but not Fgf8 (G); streak 1 expresses Fgf8 (I), but not Foxa2 (F); however, the border expresses both markers (E,H). (J-M) Transverse sections through mid-streak (St2) of E8.5 embryos hybridised with T (J), Wnt3a (K), Fgf8 (L) and Evx1 (M). Line in J marks the midline, arrows mark the lateral region grafted (Lt).