Fig. 8. Cyclopamine treatment leads to RPE defects. An embryo incubated in cyclopamine solution (B) displays an abnormal pigmentation of the RPE (arrow) compared with the control embryo (A). Whole-mount in situ hybridisation (K-N) or retinal sections after whole-mount in situ hybridisation (G-J,Q-X), or immunostaining on retinal sections (C-F,O,P) of stage 40 embryos incubated with or without cyclopamine solution, as indicated, from stage 20 onwards. The probes or the antibodies are indicated for each panel. Cyclopamine does not interfere with the staining of ß-tubulin (C,D), R2-12 (E,F), Brn3.0 (G,H; the arrow indicates the expression in the ganglion cell layer in G), Xotx2 (I,J; the arrow in I indicates the expression in the inner nuclear cell layer, while the arrowhead indicates the expression in the CMZ) or Vax2 (K,L; the arrows indicate the ventral part of the retina expressing Vax2). Pax2 expression is strongly reduced (N; the arrow in M indicates Pax2 normal expression in the ventral retina). XAR1 immunostaining is completely abolished in the RPE in cyclopamine treated embryos (arrows in P), compared with control staining (arrows in O). XMitf expression is decreased in the presence of cyclopamine in the central RPE (arrow in R compared with Q) and abolished in the more peripheral region of the RPE (arrowheads in R compared with Q). Xotx5 expression is decreased mainly in the ventral region of the RPE in cyclopamine-treated embryos (arrow in T). X-bhh and X-chh expression in cyclopamine-treated embryos is reduced in the RPE, mainly in the peripheral part of the expression domain (arrows in V and X). le, lens; GCL, ganglion cell layer; INL, inner nuclear layer; PR, photoreceptor layer. Scale bar: 300 µm in A,B,K-N; 30 µm in C,D,G-J,O-X; 20 µm in E,F.