Fig. 9

Specific suppression of the Fgf8 subfamily growth factors by sdn-R3 overexpression. Zebrafish embryos were co-injected with mRNA (250 pg/embryo) for egfp (A–E) or sdn-R3 (A′–D′ and E) together with different fgf mRNA (fgf3, fgf4, fgf8, fgf8.2, fgf16, fgf17b, fgf24) at minimal amounts sufficient to attain complete dorsalization. The effect of fgf overexpression (elongation) was examined to evaluate the suppressive effects of sdn-R3. (A–D and A′–D′) Typical results for the suppressive effects of sdn-R3 on the dorsalizing activities of fgf3, fgf4, and fgf8 are shown. The dorsalizing activity of fgf3 and fgf4, as revealed by the elongated morphology, was not affected by sdn-R3, whereas the effects of fgf8 were strongly suppressed. It should be noted that embryos co-injected with mRNA for fgf8 and sdn-R3 were no more simply elongated, but that they were distorted as shown in Fig. 8A′, which is the reason why embryos also seem slightly elongated. Importantly, the FGF signal was disrupted in these apparently elongated embryos as visualized by the downregulation of spry4 (Supplementary Fig. 2K and N, additional data not shown). Scale bars, 1 mm. (E) Embryos were judged as rescued as described in the legend to Fig. 4 and Supplementary Fig. 3B. The ordinates represent the percentages of embryos which were judged dorsalized. Co-injection was repeated three times for each combination, and the error bars show standard errors of means. The amounts of sdn-R3 and egfp mRNA are shown at the bottom of each panel.