Fig. 4

Global overexpression of CA-FgfR1 in fgf8^−/− mutants rescues focal left-sided expression of Tg(dusp6:d2EGFP). (A–D″) Confocal maximum projection (55 µm) showing the whole head (A–D) or confocal sections (A′–D″) showing the epithalamus of 32-hpf Tg(dusp6:d2EGFP) control embryos (A–B″) or Tg(dusp6:d2EGFP) fgf8^−/− mutants (C–D″) that express (B–B″ and D–D″) or not (A–A″ and C–C″) Tg(hsp70:ca-fgfr1) transgene after heat shock at 26 and 29 hpf. (Scale bars, 25 µm in A–D and 10 µm in A′–D″.) The image in A″–D″ corresponds to the image in A′–D′ (green) superimposed on nuclear staining (gray) allowing visualization of the epiphysis (white circle) and parapineal (yellow circle); embryo view is dorsal, anterior is up. (E–H′) Polar graphs showing the distribution and mean number of total (E′–H′) or Tg(dusp6:d2EGFP)⁺ (E–H) parapineal cells in each 45 °C semiquadrant (1–8) relative to the parapineal mean position (center) at 32 hpf. Cell distribution and mean number are shown for control embryos that express (F and F′; n = 11) or not (E and E′; n = 10) CA-FgfR1 transgene and for fgf8^−/− mutants that express (H and H′; n = 16) or not (G and G′; n = 12) CA-FgfR1. Radial axis (vertical scale on the left side) represent the mean number of Tg(dusp6:d2EGFP)⁺ parapineal cells (green area in E–H, scale 0–2) or all parapineal cells (gray area in E′–H′, scale 0–3) per semiquadrant and per embryo. The expression of Tg(dusp6:d2EGFP) is increased in the parapineal of embryos expressing CA-FgfR1 although it is still mosaic and enriched on the left/posterior side (B–B″ and F; n = 11) as in controls (A–A″ and E; n = 10). In fgf8^−/− embryos, Tg(dusp6:d2EGFP) is either not expressed in the parapineal or weakly detected (C–C″ and G; n = 12) while its expression is rescued in the parapineal of fgf8^−/− embryos expressing CA-FgfR1 transgene (D–D″ and H; n = 16).