A loxP site was inserted upstream of exon 2. An FRT-flanked neomycin resistance cassette with a 5' loxP site was inserted downstream of exon 2. Cre-mediated recombination removed exon 2. Flp-mediated recombination removed the neomycin resistance cassette. Western blot analysis confirmed the absence of protein expression in bone marrow-derived dendritic cells and mouse embryonic fibroblasts. (J:201909)