Using a targeting vector from the International Knockout Mouse Consortium (IKMC), the following elements were inserted: an FRT site, a lacZ beta-galactosidase reporter gene cassette (En2 splice acceptor, IRES, lacZ gene, poly(A) signal sequence), a loxP site, a neomycin resistance gene cassette, a second FRT site, and a second loxP site into intron 1 and a third loxP site into intron 2. The floxed exon 2 was deleted through subsequent cre-mediated recombination by crossing mice carrying this allele with mice carrying a Zp3-Cre allele. (J:296111)