Fig. 3. A selective antagonist of Cyp26 enzymes recapitulates the cyp26a1 ; cyp26b1;cyp26c1 phenotype. RNA in situ hybridizations with the markers described in Fig. 2. (A-F) Compared with DMSOtreated controls (A,C,E), treatment with 10 µM R115866 (B,D,F) causes an anterior shift of hoxb1a (arrowhead in A,B) and hoxd4 (arrowhead in C,D) towards the presumptive cerebellum, marked by en3 (red in A,B) and by pax2a (brackets in C-F). This effect of R115866 is reversed by co-treatment with 10 µM DEAB (E,F). Scale bars: 100 µm. Scale bar in A is for A,B; Scale bar in C is for C-F.