Figure 1

Retinoic acid and olfactory induction. (A-F) Chicken embryos treated with disulphiram-impregnated beads (100 μM in DMSO) during OP induction (HH-stage 14) show unaffected placodal development (A,C: whole-mounts; B,D: frontal sections after Dlx6 labeling) and Fgf8 expression in the placodal rim (E,F). (G-L) Raldh3^−/− mouse mutants (I,J) and Raldh2^−/−; Raldh3^−/− compound mutants (K,L) exhibit a Dlx5-labeled olfactory placode at E9.5 (G,I,K: whole-mounts; H,J,L: transverse sections). (M-R) Raldh3 is expressed within chicken (M-P) and mouse (Q) early embryonic OE. Raldh2 appears later (E11.5 in mouse) in surrounding mesenchyme (R). On the right are schemes explaining the section planes used throughout this study. Chicken and mouse embryos were sectioned according to a frontal section plane, as suggested by the colored Z-plane shown in perspective. For older mouse embryos and fetuses (Q,R, and subsequent figures), a detail of one of the nasal cavities is shown, as suggested by the boxed area in the bottom scheme. Mouse schemes are adapted from [23].