Fig. 3. PDGFR signaling is necessary for opV trigeminal placode induction in vitro. (A) Diagram of explanted conjugates. Quail ectoderm, cultured in collagen on top of chick dorsal neural tube for 18 hours, expresses opV trigeminal placode marker Pax3. PDGFR inhibitor reduces Pax3 induction. Ectoderm-derived Pax3+ cells are distinguished from neural tubes cells using quail specific marker QCPN. (B) Quantification of reduction of Pax3+ induction in explants. Pax3+ cells are reduced by 58% and 84% by 10 nM and 100 nM PIII, respectively (control, n=15 explants; 10 nM, n=15; 100 nM, n=11). (C-N) Sections of control, 10 nM, and 100 nM PDGFR inhibitor (PIII) treated explants stained with Pax3 (green), QCPN (red) and DAPI (blue). Pax3/QCPN+ cells are placode derived (arrow). DAPI shows overall health of explants. (C) Many Pax3+ cells are induced in control explants. (G) 10 nM PIII dramatically reduces number of Pax3+ cells in ectoderm. (K) At 100 nM PIII, very few Pax3+ cells are detected. Error bar=s.e.m. ^*P<0.001. ecto, ectoderm; nt, neural tube.