A loxP site was inserted upstream of exon 1. An FRT-flanked neomycin resistance cassette with a 3' loxP site was inserted downstream of exon 1. Flp-mediated recombination removed the selection cassette and left exon 1 floxed. Cre-mediated recombination removed exon 1. Immunohistochemistry confirmed teh absence of protein expression in the adrenal gland. (J:278935)