The recombinase site flanked reporter cassette (FRT site, engrail2 splice acceptor, IRES, LacZ, polyadenylation sequence and loxP site) and selection cassettes (beta-geo, polyadenylation site, FRT site and loxP site) were inserted upstream of exon 5. An additional loxP site was inserted downstream of exon 6. (J:186412)