A loxP site was inserted upstream of the start codon in exon 1. A loxP site, GFP reporter gene, polyadenylation sequence, and FRT-flanked neomycin resistance cassette were inserted into intron 1. Flp-mediated recombination removed the selection cassette. Cre-mediated recombination removed the coding sequence of exon 1. (J:226158)