Site-specific genome editing provides a promising approach for achieving long-term, stable therapeutic gene expression.
Genome editing has been successfully applied in a variety of preclinical models, generally focused on targeting the
diseased locus itself; however, limited targeting efficiency or insufficient expression from the endogenous promoter may
impede the translation of these approaches, particularly if the desired editing event does not confer a selective growth
advantage. Here we report a general strategy for liver-directed protein replacement therapies that addresses these issues:
zinc finger nuclease (ZFN) –mediated site-specific integration of therapeutic transgenes within the albumin gene. By using
adeno-associated viral (AAV) vector delivery in vivo, we achieved long-term expression of human factors VIII and IX (hFVIII
and hFIX) in mouse models of hemophilia A and B at therapeutic levels. By using the same targeting reagents in wild-type
mice, lysosomal enzymes were expressed that are deficient in Fabry and Gaucher diseases and in Hurler and Hunter
syndromes. The establishment of a universal nuclease-based platform for secreted protein production would represent a
critical advance in the development of safe, permanent, and functional cures for diverse genetic and nongenetic diseases.