Fig. 5.

Cell fate analysis of the anterior pineal complex indicates that parapineal precursors adopt a cone photoreceptor fate in fgf8a^x15 mutants. (A) Fate analysis scheme. Green, fluorescein-positive cells; red, Arr3a-positive cells; yellow, cells expressing both fluorescein and Arr3a. (B-C′) Dorsal views of serial confocal sections in the pineal complex of WT (B,B′) or fgf8a^x15 (C,C′) zebrafish embryos at 52 hpf, after labeling of the anterior pineal complex anlage at 24 hpf. In WT, clusters of labeled parapineal cells are evident (blue arrowheads). In fgf8a mutants, many of the cells that were labeled in the anterior pineal complex anlage at 24 hpf become cone photoreceptors (blue arrowheads). (D) When Fgf signaling is reduced, a significantly higher percentage of labeled cells become cone photoreceptors compared with controls (^**P<0.005 by t-test). Error bars represent s.e.m. Scale bar: 30 μm.