The targeting construct inserted into intron 4 an FRT site, engrailed splice acceptor, IRES sequence, EGFP reporter gene, polyadenylation sequence, loxP, FRT site, and loxP site. An additional loxP site was inserted downstream of exon 5. Flp-mediated recombination removed the reporter and selection cassette. Cre-mediated recombination removed exon 5. (J:316087)