Fig. 5. Exogenous RA disrupts cyp26b1 and cyp26c1 expression in cyp26a1^-/- embryos but not in wild type. cyp26b1 (A-D) and cyp26c1 (E-H) expression (blue) is established normally in wild-type (A,E) and cyp26a1^-/- (B,F) embryos at the 6-somite stage (12 hpf). cyp26b1 and cyp26c1 expression is also established normally in wild-type embryos treated with a sub-teratogenic concentration of RA (5 nM; C,G), but not in cyp26a1^-/- embryos treated with 5 nM RA (D,H). krox20 expression is shown in red.