The targeting construct replaced the coding sequence with a loxP site, FRT-flanked neomycin resistance cassette, the human coding sequence for isoform 3 (E3F) with signal peptide, an F3 flanked puromycin resistance cassette, loxP site, and human GH polyadenylation sequence. Flp-mediated recombination removed the FRT-flanked neomycin resistance cassette. (J:311531)