A loxP site was inserted upstream of exon 2. An FRT-flanked neomycin resistance cassette with a 3' loxP site was inserted downstream of exon 4. Flp-mediated recombination removed the neomycin resistance cassette. Cre-mediated recombination removed exons 2 through 4 floxed. Western blot analysis confirmed the absence of protein expression in the brain and lung.