A loxP site was inserted into intron 1 and an FRT site flanked neomycin resistance gene cassette, loxP site, and splice acceptor and EGFP cassette were inserted into intron 4 via homologous recombination. Subsequent flp-mediated recombination removed the neo cassette and cre-mediated recombination deleted exons 2-4. (J:211639)