Fig. 5. Ectopic Sox9 expression suppresses neurogenesis. Immunohistochemical detection of neural progenitor markers (A-I) and interneuron markers (J-R) on transverse sections of neural tubes 24 hours (A-I) and 48 hours (J-R) after electroporation with Sox9. Ectopic Sox9 suppresses Pax7 (A-C), Pax6 (D-F) and Nkx6 (G-I) expression in the neural progenitor cells in a cell-autonomous manner. Moreover, neuronal differentiation is inhibited by Sox9 expression. Induction of Lbx1-expressing interneurons in the dorsal neural tube is inhibited by Sox9 expression (J-L), as are the induction of Pax2-expressing interneurons (M-O) and HB9/MNR2-expressing motor neurons (P-R). The effect of Sox9 is cell autonomous, with untransfected cells differentiating into neuronal subtypes in a position-appropriate manner.