Fig. 3. Loss of RARE function affects Cdx1 expression in vivo. Whole-mount in situ hybridization analysis of Cdx1 expression in wild type (A,C,E) and RARE mutants (B,D,F). All stages to be compared were processed and stained in parallel. (A,B) Analysis of early E7.0 to late head folds stages demonstrates onset of Cdx1 expression at late primitive streak stages (E7.5) in both wild-type (A) and RARE mutant embryos (B). Dark field micrographs are shown for ease of stage comparison. (C,D) Wild-type (C) and RARE mutant (D) embryos ranging from 1 (left) to 7 (right) somites. Note the diminution of expression in mutant embryos relative to stage matched controls. (E,F) Wild-type (E) and RARE mutant (F) embryos ranging from 7 (left) to 13 or 14 (right) somites. Note the near loss of expression in the mutants relative to stage matched controls.