Exons 7, 8, and 9 of the gen were targeted by inserting a single loxP site in intron 6 and an FRT-flanked neomycin resistance gene coupled with a loxP site in intron 9. The loxP sites flank the sequences encoding the DPWW active motif. The FRT-flanked neomycin selection cassette was removed via FLP-mediated recombination. (J:247703)