title: Multiple effects of genetic background on variegated transgene expression in mice.
abstract: BLG/7 transgenic mice express an ovine beta-lactoglobulin transgene during lactation. Unusually, transgene expression levels in milk differ between siblings. This variable expression is due to variegated transgene expression in the mammary gland and is reminiscent of position-effect variegation. The BLG/7 line was created and maintained on a mixed CBA x C57BL/6 background. We have investigated the effect on transgene expression of backcrossing for 13 generations into these backgrounds. Variable transgene expression was observed in all populations examined, confirming that it is an inherent property of the transgene array at its site of integration. There were also strain-specific effects on transgene expression that appear to be independent of the inherent variegation. The transgene, compared to endogenous milk protein genes, is specifically susceptible to inbreeding depression. Outcrossing restored transgene expression levels to that of the parental population; thus suppression was not inherited. Finally, no generation-dependent decrease in mean expression levels was observed in the parental population. Thus, although the BLG/7 transgene is expressed in a variegated manner, there was no generation-associated accumulated silencing of transgene expression.
authors.affiliation: Roslin Institute (Edinburgh), Division of Molecular Biology, Roslin, Midlothian, EH25 9PS, United Kingdom.
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Opsahl
authors.forename: Margaret
authors.initials: M
authors.lastname: McClenaghan
authors.forename: Anthea
authors.initials: A
authors.lastname: Springbett
authors.forename: Sarah
authors.initials: S
authors.lastname: Reid
authors.forename: Richard
authors.initials: R
authors.lastname: Lathe
authors.forename: Alan
authors.initials: A
authors.lastname: Colman
authors.forename: C Bruce A
authors.initials: CB
authors.lastname: Whitelaw
mesh_terms: D000818:Animals; D003433:Crosses, Genetic; D015870:Gene Expression; D007178:Inbreeding; D007782:Lactoglobulins / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic / Q000235:genetics; D019076:Transgenes
chemical_list: D007782:Lactoglobulins