A loxP site was inserted upstream of exon 11. An FRT-flanked neomycin resistance cassette with a 3' loxP site was inserted downstream of exon 12. Flp-mediated recombination removed the neomycin resistance cassette. Cre-mediated recombination removed exons 11 and 12. Western blot analysis confirmed the absence of protein expression in the heart, lung, liver, kidney and spleen. (J:203735)