A loxP site flanked neomycin resistance gene cassette was inserted into intron 4 and point mutations were introduced into exon 5, resulting in the substitution of proline 202 and phenylalanine 203 with alanines (p.(P202_F203delinsAA)) in the encoded proetin. Livers from homozygous mice show increased expression of the mutant mRNA and protein compared to endogenous gene expression in wild-type controls. Subcellular localization of the mutant protein is similar to wild-type.