A loxP (L83) site was inserted upstream of the promoter and FRT-flanked neomycin cassette and a second loxP site were inserted downstream of intron 1. Flp-mediated recombination removed the neomycin cassette. Cre-mediated recombination removed the promoter and exon 1. Western blot analysis confirmed absence of protein in the liver, spleen, and kidney. (J:243276)