Fig. 4. RA alters the expression of early AP-specific genes. Dorsal views of whole embryos at late gastrula stage. Embryos at the 40% epiboly stage were treated with 10^–6 M RA for 80 minutes. The embryos were fixed at the 80 to 90% epiboly stage, and stained with cyp26 (A,B), hoxb1b (C,D), meis3 (E,F) or otx2 (G,H). The posterior genes hoxb1b and meis3 were ectopically induced in the anterior region by RA (B,D), while the anterior gene otx2 was suppressed (H). Although cyp26 is expressed in the anterior region, its expression was activated by RA(B).

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