A targeting vector containing DreER cDNA, SV40 poly(A) sequence and Frt site-flanked PGK-EM7-Neo resistance gene was used to insert a cDNA encoding Dre recombinase fused with a mutant form of the estrogen-receptor hormone-binding domain in frame with the translational start codon (ATG) of the Sftpc gene. (J:278107)