One loxP site was inserted in intron 3 just 5' to exon 4. A neomycin resistance cassette, a second loxP site and an EGFP construct were inserted 3' to exon 8. Cre mediated excision will remove exons 4-8 and the resistance cassette. This results in a fusion protein composed of exons 1-3 and EGFP.