Site-specific genomic integration produces therapeutic Factor IX levels in mice

Nat Biotechnol. 2002 Nov;20(11):1124-8. doi: 10.1038/nbt753. Epub 2002 Oct 15.


We used the integrase from phage phiC31 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 approximately 4 microg/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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Factor IX / biosynthesis*
  • Factor IX / genetics*
  • Gene Expression Regulation
  • Genetic Therapy / methods
  • Genome
  • Injections, Intravenous
  • Integrases / genetics
  • Integrases / metabolism
  • Liver / drug effects
  • Liver / metabolism*
  • Liver / physiology
  • Mice
  • Mice, Inbred C57BL
  • Mutagenesis, Site-Directed*
  • Plasmids / administration & dosage
  • Plasmids / genetics
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Sequence Analysis, DNA


  • Factor IX
  • Integrases