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Fig. 1
Developmental response to various concentrations of different RA isomers. (A) Isomerization reaction of 13-cis RA into all-trans RA (and vice versa). (B) Typical phenotype of a zebrafish embryo incubated in embryo medium (EM) and in DEAB. Note the enlarged heart cavity (area enclosed by yellow line). (C) Developmental response of embryos incubated in DEAB to transient (5-minute) incubation in various concentrations of all-trans RA, 9-cis RA and 13-cis RA, subjected or not to UV illumination and fixed in 4% paraformaldehyde at 33 hpf. Since the heart cavity is enlarged in DEAB, we used the ratio of its transverse area (as enclosed by the yellow line in B) to the value in DEAB as a means to quantify the rescue (which is maximal when the ratio is minimal). Note that rescue of heart development requires <1 nM all-trans RA, 10 nM 9-cis RA or 5 nM 13-cis RA plus UV illumination (1 minute). No rescue is observed in up to 50 nM 13-cis RA. The number of embryos used for each condition is <20. Error bars indicate s.d.