The development of non-viral gene-transfer technologies that can support stable chromosomal integration and persistent gene expression in vivo is desirable. Here we describe the successful use of transposon technology for the nonhomologous insertion of foreign genes into the genomes of adult mammals using naked DNA. We show that the Sleeping Beauty transposase can efficiently insert transposon DNA into the mouse genome in approximately 5-6% of transfected mouse liver cells. Chromosomal transposition resulted in long-term expression (>5 months) of human blood coagulation factor IX at levels that were therapeutic in a mouse model of haemophilia B. Our results establish DNA-mediated transposition as a new genetic tool for mammals, and provide new strategies to improve existing non-viral and viral vectors for human gene therapy applications.

These results suggest that biglycan may bind apoE and apoB in atherosclerotic intima. They also raise the possibility that apoE may act as a "bridging" molecule that traps apoA-I-containing HDL in atherosclerotic intima. Taken together, these findings are consistent with the hypothesis that biglycan may contribute to the pathogenesis of atherosclerosis by trapping lipoproteins in the artery wall.

Human-immunodeficiency-virus (HIV)-based lentiviral vectors are a promising tool for in vivo gene therapy. Unlike Moloney-murine-leukaemia-based retroviruses (MLV), lentiviruses are believed to stably transduce quiescent (non-cycling) cells in various organs. No previous studies, however, have directly established the cell-cycle status of any transduced cell type at the time of vector administration in vivo. In vitro studies using wild-type HIV or HIV-based vectors have shown that, in some cases, cell-cycle activation is required for infection, even though cellular mitosis is not an absolute requirement for integration. Even if the block in reverse transcription is overcome in quiescent T cells, productive infection by HIV cannot be rescued in the absence of cell-cycle activation. The potential use of these vectors for gene therapy prompted our study, which establishes a cell-cycle requirement for efficient transduction of hepatocytes in vivo.

Recombinant adeno-associated virus vectors (rAAV) show promise in preclinical trials for the treatment of genetic diseases including hemophilia. Liver-directed gene transfer results in a slow rise in transgene expression, reaching steady-state levels over a period of 5 weeks concomitant with the conversion of the singlestranded rAAV molecules into high-molecular-weight concatemers in about 5% of hepatocytes. Immunohistochemistry and RNA in situ hybridization show that the transgene product is made in about ϳ5% of hepatocytes, suggesting that most rAAV-mediated gene expression occurs in hepatocytes containing the doublestranded concatemers. In this study, the mechanism(s) involved in stable transduction in vivo was evaluated. While only ϳ5% of hepatocytes are stably transduced, in situ hybridization experiments demonstrated that the vast majority of the hepatocytes take up AAV-DNA genomes after portal vein infusion of the vector. Two different vectors were infused together or staggered by 1, 3, or 5 weeks, and two-color fluorescent in situ hybridization and molecular analyses were performed 5 weeks after the infusion of the second vector. These experiments revealed that a small but changing subpopulation of hepatocytes were permissive to stable transduction. Furthermore, in animals that received a single infusion of two vectors, about one-third of the transduced cells contained heteroconcatemers, suggesting that dimer formation was a critical event in the process of concatemer formation. To determine if the progression through the cell cycle was important for rAAV transduction, animals were continuously infused with 5-bromo-2-deoxyuridine (BrdU), starting at the time of administration of a rAAV vector that expressed cytoplasmic ␤-galactosidase. Colabeling for ␤-galactosidase and BrdU revealed that there was no preference for transduction of cycling cells. This was further confirmed by demonstrating no increase in rAAV transduction efficiencies in animals whose livers were induced to cycle at the time of or after vector administration. Taken together, our studies suggest that while virtually all hepatocytes take up vector, unknown cellular factors are required for stable transduction, and that dimer formation is a critical event in the transduction pathway. These studies have important implications for understanding the mechanism of integration and may be useful for improving liver gene transfer in vivo.

Collectively, these results suggest that oxidative processes may regulate GPI-PLD expression and suggest a role for GPI-PLD in inflammation and in the pathogenesis of atherosclerosis.