Fig. 4. Cdx1 is induced by RA in RARE-null mutants. In situ hybridization analysis of Cdx1 expression of wild-type (A,B,E,F,I,J,M,N) or Rare^-/- (C,D,G,H,K,L,O,P) embryos following treatment with vehicle (A,C,E,G,I,K,M,O) or RA (B,D,F,H,J,L,N,P) at E7 (A-D), E7.5 (E-H), E8.0 (I-L) or E8.5 (M-P). All embryos were recovered 4 hours after in utero treatment with RA and equivalent stage matched samples processed in parallel for analysis. Note that Cdx1 was induced by RA at gastrulation stages, with induction seen in both wild-type (A versus B) and RARE mutants (C versus D). Induction also occurred at all later stages irrespective of genotype.