title: Coexpression after electroporation of plasmid mixtures into muscle in vivo.
abstract: OBJECTIVE
  Muscle is perhaps the most frequently considered tissue for non-viral gene therapy, in particular after gene transfer by electroporation. Expression in muscle is stable, but since the cell turnover is so slow incorporation in the host genome is not required. This raises interesting practical and theoretical questions related to the behaviour of the transgenic DNA under such conditions.
  
  
  METHODS
  We have investigated expression of reporter genes from plasmid mixtures electroporated into the extensor digitorum longus (EDL) muscle in mice in order to assess the degree of coexpression.
  
  
  RESULTS
  Under conditions where the reporter is easily identified the coexpression rate was 100%, as none of 287 fibres from five different muscles expressing blue fluorescent protein (BFP) failed to express green fluorescent protein (GFP). With other reporter combinations the rate was lower, but this we attribute to marginal sensitivity for fluorescent proteins, or from reporter protein degradation for beta-galactosidase.
  
  
  CONCLUSIONS
  The high degree of coexpression suggests that a large copy number takes part in the final transcription with this system. The finding also enhances the usefulness of muscle and electroporation for gene therapy and experimental biology.
authors.affiliation: Department of Molecular Biosciences, University of Oslo, Blindern, Oslo, Norway.
authors.forename: Z A
authors.initials: ZA
authors.lastname: Rana
authors.forename: M
authors.initials: M
authors.lastname: Ekmark
authors.forename: K
authors.initials: K
authors.lastname: Gundersen
mesh_terms: D000818:Animals; D018274:Electroporation / Q000379:methods; D005260:Female; D015870:Gene Expression / Q000235:genetics*; D017930:Genes, Reporter / Q000235:genetics*; D049452:Green Fluorescent Proteins; D007202:Indicators and Reagents / Q000032:analysis; D008164:Luminescent Proteins / Q000032:analysis; D051379:Mice; D008815:Mice, Inbred Strains; D008856:Microscopy, Fluorescence / Q000379:methods; D018482:Muscle, Skeletal / Q000502:physiology*; D010957:Plasmids / Q000235:genetics*; D014162:Transfection; D001616:beta-Galactosidase / Q000032:analysis
chemical_list: D007202:Indicators and Reagents; D008164:Luminescent Proteins; C409504:blue fluorescent protein, Aequorea victoria; D049452:Green Fluorescent Proteins; D001616:beta-Galactosidase