title: Genotypic features of lentivirus transgenic mice.
abstract: Lentivector-mediated transgenesis is increasingly used, whether for basic studies as an alternative to pronuclear injection of naked DNA or to test candidate gene therapy vectors. In an effort to characterize the genetic features of this approach, we first measured the frequency of germ line transmission of individual proviruses established by infection of fertilized mouse oocytes. Seventy integrants from 11 founder (G0) mice were passed to 111 first generation (G1) pups, for a total of 255 events corresponding to an average rate of transmission of 44%. This implies that integration had most often occurred at the one- or two-cell stage and that the degree of genotypic mosaicism in G0 mice obtained through this approach is generally minimal. Transmission analysis of eight individual proviruses in 13 G2 mice obtained by a G0-G1 cross revealed only 8% of proviral homozygosity, significantly below the 25% expected from purely Mendelian transmission, suggesting counter-selection due to interference with the functions of targeted loci. Mapping of 239 proviral integration sites in 49 founder animals revealed that about 60% resided within annotated genes, with a marked tendency for clustering in the middle of the transcribed region, and that integration was not influenced by the transcriptional orientation. Transcript levels of a set of arbitrarily chosen target genes were significantly higher in two-cell embryos than in embryonic stem cells or adult somatic cells, suggesting that, as previously noted in other settings, lentiviral vectors integrate preferentially into regions of the genome that are transcriptionally active or poised for activation.
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, School of Life Sciences, Lausanne CH-1015, Switzerland.
authors.forename: Marc-Olivier
authors.initials: MO
authors.lastname: Sauvain
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Dorr
authors.forename: Brian
authors.initials: B
authors.lastname: Stevenson
authors.forename: Alexandra
authors.initials: A
authors.lastname: Quazzola
authors.forename: Félix
authors.initials: F
authors.lastname: Naef
authors.forename: Maciej
authors.initials: M
authors.lastname: Wiznerowicz
authors.forename: Frédéric
authors.initials: F
authors.lastname: Schütz
authors.forename: Victor
authors.initials: V
authors.lastname: Jongeneel
authors.forename: Denis
authors.initials: D
authors.lastname: Duboule
authors.forename: François
authors.initials: F
authors.lastname: Spitz
authors.forename: Didier
authors.initials: D
authors.lastname: Trono
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D005822:Genetic Vectors; D016086:Lentivirus / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic / Q000821:virology*; D009030:Mosaicism; D011533:Proviruses / Q000235:genetics; D016662:Virus Integration; D014918:Wills