Nature Biotechnology20, 1124 - 1128 (2002)
Published online: 15 October 2002; | doi:10.1038/nbt753
Site-specific genomic integration produces therapeutic Factor IX levels in mice
Eric C. Olivares1, Roger P. Hollis1, Thomas W. Chalberg1, Leonard Meuse2, Mark A. Kay2
& Michele P. Calos1
1
Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305.
2
Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94305.
Correspondence should be addressed to Michele P. Calos calos@stanford.edu
We used the integrase from phage C31 to integrate the human Factor IX (hFIX) gene permanently into specific sites in the mouse genome. A plasmid containing attB and an expression cassette for hFIX was delivered to the livers of mice by using high-pressure tail vein injection. When an integrase expression plasmid was co-injected, hFIX serum levels increased more than tenfold to 4 g/ml, similar to normal FIX levels, and remained stable throughout the more than eight months of the experiment. hFIX levels persisted after partial hepatectomy, suggesting genomic integration of the vector. Site-specific integration was proven by characterizing and quantifying genomic integration in the liver at the DNA level. Integration was documented at two pseudo-attP sites, native sequences with partial identity to attP, with one site highly predominant. This study demonstrates in vivo gene transfer in an animal by site-specific genomic integration.
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C31 to integrate the human Factor IX (hFIX) gene permanently into specific sites in the mouse genome. A plasmid containing attB and an expression cassette for hFIX was delivered to the livers of mice by using high-pressure tail vein injection. When an integrase expression plasmid was co-injected, hFIX serum levels increased more than tenfold to 
4 
g/ml, similar to normal FIX levels, and remained stable throughout the more than eight months of the experiment. hFIX levels persisted after partial hepatectomy, suggesting genomic integration of the vector. Site-specific integration was proven by characterizing and quantifying genomic integration in the liver at the DNA level. Integration was documented at two pseudo-attP sites, native sequences with partial identity to attP, with one site highly predominant. This study demonstrates in vivo gene transfer in an animal by site-specific genomic integration.
C31 integrase
