Fig. 5. (A-C,N-R) Immunostaining of sections of tadpole eyes with antibodies against rhodopsin and calbindin. (D-M) Whole-mount staining of tadpoles with antibodies against rhodopsin. (A) Section of a stage 39 tadpole that does not carry the Xrx1A-FGFR4a construct stained with antibodies against rhodopsin, demonstrating the presence of photoreceptor cells. (B) Section of a stage 39 tadpole that carries the Xrx1A-FGFR4a construct stained with antibodies against rhodopsin. Note the lack of photoreceptor cells. (C) Section of a tadpole carrying the Xrx1A-FGFR4a construct stained with rhodopsin antibodies that shows some photoreceptor cells in ectopic position. (D-G) Whole-mount staining of Xenopus tadpoles that do not carry the Xrx1A-FGFR4a construct with rhodopsin antibodies at different stages, demonstrating the normal accumulation of photoreceptor cells during development. (H-M) Whole-mount staining of transgenic Xenopus tadpoles expressing the Xrx1A-FGFR4a construct with rhodopsin antibodies at different stages, demonstrating lower numbers of photoreceptor cells in these embryos at all stages. D,H, stage 33; E,K, stage 35; F,L, stage 36; G,M, stage 38. (N) Staining of a section from a stage 46 embryo that does not carry the Xrx1A-FGFR4a construct with antibodies against rhodopsin. (O) Staining of a section of stage 45 embryo that does not carry the Xrx1A-FGFR4a construct with antibodies against cone-specific calbindin. (P) An eye section from a stage 45 tadpole expressing the Xrx1A-FGFR4a construct stained with rhodopsin antibodies. Note the lack of rhodopsin-positive rods. (R) An eye section from a stage 45 tadpole expressing the Xrx1A-FGFR4a construct stained with calbindin antibodies. Only few cones are present (arrowheads), some of them in ectopic locations.