A GC to AG change at position 518-519 resulting in an arginine to glutamine substitution at amino acid 173 (R173Q) was introduced in exon 10 and a loxP-flanked neomycin cassette was inserted in intron 9. The neomycin selection cassette was removed via cre-mediated recombination. This is a mutation found in human dominant acute intermittent porphyria. (J:275245)