Fig. 8. Modulation of Hh signaling can promote OPC specification at the expense of secondary motoneurons. (A,C,E) Transverse sections, dorsal upwards, of Tg[olig2:egfp] embryos labeled with pan-neuronal anti-Hu antibody (red). Asterisks and arrows mark OPCs and radial cells, respectively. (B,D,F) Lateral views of intact Tg[olig2:egfp] embryos, dorsal upwards and anterior leftwards. Brackets indicate dorsal spinal cord. (A,B) Untreated embryos showing normal number and distribution of OPCs. (C,D) Embryos treated with cyclopamine from 11-26 hpf had few OPCs. (E,F) Embryos treated from 14-26 hpf had excess OPCs. (G) Quantification of effects on SMNs and OPCs. Embryos were labeled with anti-Neurolin antibody to reveal SMNs. A total of 20 sections were counted from four embryos for each experiment. Scale bar: 20 µm for top row; 80 µm for bottom row.