One loxP site was inserted just upstream of exon 2 and a second loxP site 61 bp into exon 3. An FRT flanked neomycin resistance gene cassette was inserted into intron 1. Flp mediated recombination removed the neo cassette. The sequence representing exon 2 through most of exon 3 was deleted through cre-mediated recombination. Western blot analysis confirmed the absence of protein expression in brain, lung, liver, pancreas, and thymus lysates from homozygous mutant mice.