Fig. 7. Expression of a constitutively activated Smad2 (Smad2-2E) induces caudal Hox protein expression at the expense of rostral Hox protein expression. (A-C) Western analyses of pSmad1/5/8 and pSmad2/3 levels in neural plate explants treated with Gdf11 (A), in Gdf11 electroporated chick embryos (B) and in E9.5 Gdf11^-/- mouse embryos (C). (D-M) Hoxc6-Hoxc10 expression in longitudinally sectioned (D-H) and in cross-sectioned (I-M) HH stage 25 spinal cords 3 days after Smad2-2E electroporation. The electroporated side (on the right in all panels) is marked by GFP expression. Enlarged image of boxed areas are shown below each panel. White arrows indicate the inhibition of Hoxc6 (D,I) and Hoxc8 (E,J) expression, and the induction of Hoxc9 (F,K) and Hoxc10 (G,L) expression by Smad2-2E expression. Double labeling of Hoxc6 and Hoxc9 (H,M) demonstrate the Hoxc9⁺ cells (white arrows) induced by Smad2-2E in the Hoxc6 domain do not express Hoxc6. (D,F,H) The same section; (I,K,M) the same section. Scale bars: 50 µm.