Fig. 4. PDGFR signaling is necessary for opV trigeminal placode induction in vivo. Vehicle control (A,C,E) or 2.5 µm PIII (B,D,F) was focally injected into the right midbrain-level mesenchyme at st. 8. At st. 10, Pax3 (green) in ectoderm marks (arrows) induced opV trigeminal placode cells. DAPI (black or blue) indicates total cell number. (A) In control embryos, Pax3 is expressed in many cells in the ectoderm. (B) 2.5 µm PIII significantly reduces Pax3+ cells in the ectoderm. (A'-F') Higher magnification of white box in matched panels A-F.