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 5. Flp-mediated recombination removed the neomycin resistance cassette and left exons 2 through 5 floxed. Cre-mediated recombination removed exons 2 through 5. Western blot analysis confirmed the absence of protein expression in neonatal mouse epidermis. (J:196489)