LoxP site was inserted into intron 1 and a loxP site and frt-flanked neimycin selection cassette was inserted into intron 6. Cre mediated recombination resulted in the deletion of exons 2-6 and the neomycin selection cassette. Western blot analysis shows that the encoded protein is undetectable in mouse embryonic fibroblasts derived from homozygous mice. (J:251884)