A loxP site was inserted upstream of exon 1. An expression cassette (loxP site and FRT-flanked splice acceptor, IRES, EGFP and neo) was inserted into the 3' UTR. Flp-mediated recombination removed the splice acceptor, IRES, EGFP and neo. Exons 1 and 2 remain floxed. (J:194760)