Herpes simplex virus/Sleeping Beauty Vector-based embryonic gene transfer using the HSB5 mutant: loss of apparent transposition hyperactivity in vivo


  • S. de Silva
  • M.A. Mastrangelo
  • L.T. Lotta
  • C.A. Burris
  • Z. Izsvak
  • Z. Ivics
  • W.J. Bowers


  • Human Gene Therapy


  • Hum Gene Ther 21 (11): 1603-1613


  • The Sleeping Beauty (SB) transposon system has been successfully utilized as a gene delivery tool in non-viral and viral vector platforms. Since its initial reconstruction, a series of hyperactive mutants of SB have been generated. Questions remain as to whether the enhanced in vitro activities of these SB transposase mutants translate to the in vivo setting, and whether such increased integration efficiencies will ultimately compromise the safety profile of the transposon platform by raising the risk of genomic insertional mutagenesis. Herein, we compared the in vivo impact of a Herpes simplex virus (HSV) amplicon-vectored "wild-type" SB transposase (SB10) and a hyperactive SB mutant (HSB5), co-delivered in utero with the HSVT-betageo transposable reporter amplicon vector to embryonic day 14.5 C57BL6 mice. The SB10 and HSB5 transposases do not disparately affect the viability and development of injected mouse embryos. Quantitation of brain-resident betageo expression at postnatal day 21 revealed that mice receiving HSB5 exhibited only a trending increase in transgene expression compared to the SB10-infused group, an outcome that did not mirror the marked enhancement of HSB5-mediated transposition observed in vitro. These findings indicate that in vivo application of hyperactive SB mutants, while not differentially genotoxic to the developing mouse embryo, does not necessarily provide a significant "therapeutic" advantage over the employment of a lesser active SB when delivered in the context of the HSV/SB amplicon platform.