The targeting construct is designed to introduce a C420R point mutation (T2928C; TGT - CGT) into exon 8 of the gene with flanking loxP sites in introns 7 and 9. An FRT-flanked cassette containing the engrailed-2 strong splice acceptor and a reverse-orientation neomycin cassette under the control of the PGK promoter was also inserted immediately downstream of the intron 9 loxP site. (J:101977)