Fig. 5. RA induction of Cdx1 in RARE-null mutants is independent of de novo protein synthesis. RARE-null mutant E8.5 embryos were cultured for 4 hours with vehicle (A), 10^-6 M RA (B), cycloheximide (C) or cycloheximide plus RA (D; all cycloheximide cultures were initiated 30 minutes prior to addition of RA). Note that cycloheximide did not prevent RA induction of Cdx1 in the RARE-null mutants (compare D with B). The embryos are arranged to represent stage-matched samples between the four panels, with those on top possessing 8-12 somites and those on the bottom having between one and eight somites.