The targeting construct introduced into intron 13 a loxP site, minigene contains exons 14 through 18 and an FRT and loxP site flanked neomycin resistance cassette. The mini gene exon 14 sequence was modified to introduce the nucleotide substitution of AG to CA that results in the amino acid substitution of glutamine for arginine at position 367 (R367Q). (J:257751)