The targeting construct introduced upstream of exon 5 an FRT site, lacZ reporter gene, FRT site, neomycin resistance cassette, FRT site, and loxP site. A second loxP site was inserted downstream of exon 5. Cre-mediated recombination removed exon 5 and left the reporter/selection cassette intact. Flp-mediated recombination removed the reporter/selection cassette. (J:326301)