A targeting vector, containing human PCSK9 cDNA under the control of a 2.34 kb mouse albumin promoter/enhancer and a floxed cassette containing cre recombinase cDNA under the control of a 698 bp testis-specific angiotensin converting enzyme promotor and neomycin phosphotransferase selection marker driven by the pol II promoter, was inserted into the endogenous locus. Flp-mediated recombination removed the floxed cre and neo cassette.