A loxP site was inserted upstream of exon 67 and an FRT-flanked PGK-neomycin cassette and second loxP site were inserted downstream of the 3 UTR. In addition, a triple HA epitope-tag was inserted in frame at the C-terminus. The floxed region harbors the nuclear localization signal and the PC2-binding site and is a site for pathogenic mutations in humans. (J:296109)