A DNA fragment that contained a loxP sequence and pgk-1 promoter-driven neomycin phosphotransferase gene (Neo cassette) flanked by two Flp recognition target (frt) sites was inserted into a site 107 bp upstream of exon 11. The pgk-1 polyadenylation (poly-A) signal sequence was inserted downstream of the Neo cassette. The other loxP site was introduced into a site 113 bp downstream of exon 11 to eliminate the putative transmembrane domain after Cre-mediated recombination. (J:279639)