Transient developmental exposure to RA disrupts cyp26a1 expression during somitogenesis. A) Embryos were exposed to 5 nM RA from 6 to 12 hpf, and RNA was collected at 12 hpf. cyp26a1 expression levels at 12 hpf in embryos exposed to 5 nM RA. (Data represent fold change relative to control exposed embryos, means±se, n=3.) ***P < 0.001, independent samples t test. B–E) Representative images at 24 hpf showing measurements of cyp26a1 transcript detected by in situ hybridization and protein levels detected by IHC in controls (B, D) as compared to RA-exposed embryos (C, E).