A targeting construct was generated in which exons 1 and 2 was flanked with loxP sites placed 2.6 kb upstream of exon 1 in the 5 UTR and 2.6 kb downstream of exon 2 within intron 2. For selection, a neomycin (Neo) cassette flanked by frt recombination sites was also inserted into intron 2. FLP-mediated recombination in the germline removed the neomycin cassette. (J:263909)