Fig. 2. The targeted mutation of the RARE abrogates RA-response in tissue culture. F9 embryocarcinoma cells were transfected with 1.5 µg of wild-type (Wt) Cdx1 reporter, a reporter with a mutated RARE (Mut) or an RARE equivalent to the targeted mutation after Cre-mediated recombination (Lox mut). Twenty-four hours after transfection, cells were treated with vehicle or 10^-6 M RA and luciferase activity assessed 24 hours post-treatment. Results, from independent triplicate experiments, were expressed as fold RA-induction relative to vehicle treated cells. Each transfection was repeated at least twice with similar results.