A FRT site flanked neomycin resistance cassette was inserted in intron 3 along with loxP sites upstream of exon 3 and immediately downstream of the resistance cassette. The neo cassette was removed via Flp-mediated recombination and the loxP flanked exon 3 was deleted via Cre-mediated recombination. Western blot analysis confirmed absence of protein in all tissues examined. (J:204620)