Satellite DNA induces unstable expression of the adjacent herpes simplex virus tk gene cotransfected in mouse cells.

Talarico, Daniela; Peverali, A F; Ginelli, E; Meneveri, R; Mondello, C; Valle, G Della

doi:10.1128/mcb.8.3.1336

Cited by 8 publications

(1 citation statement)

References 38 publications

(65 reference statements)

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“…A transgene inserted into the X chromosome (10) or an X-autosome translocation (20) generates mosaic expression due to stochastic X chromosome inactivation. Silencing has also been observed when the transgene integrates into repeat sequence or satellite DNA (11,12), whereas different levels of transgene expression between animals of the same lineage have been attributed to strain-specific modifier genes (13-15).…”

Section: Introductionmentioning

confidence: 99%

Variegated transgene expression in mouse mammary gland is determined by the transgene integration locus.

Dobie

Lee

Fantes

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

139

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Mice carrying an ovine 18-lactoglobulin (BLG) transgene secrete BLG protein into their milk. To explore transgene expression stability, we studied expression levels in three BLG transgenic mouse lines. Unexpectedly, two lines exhibited variable levels of transgene expression. Copy number within lines appeared to be stable and there was no evidence of transgene rearrangement. In the most variable line, BLG production levels were stable within individual mice in two successive lactations. Backcrossing demonstrated that genetic background did not contribute significantly to variable expression. Tissue in situ hybridization revealed mosaicism of transgene expression within individual mammary glands from the two variable lines; in low expressors, discrete patches of cells expressing the transgene were observed. Transgene protein concentrations in milk reflected the proportion of epithelial cells expressing BLG mRNA. Furthermore, chromosomal in situ hybridization revealed that transgene arrays in both lines are situated close to the centromere. We propose that mosaicism of transgene expression is a consequence of the chromosomal location and/or the nature of the primary transgene integration event.f3-Lactoglobulin (BLG) is a major ovine milk protein. The function of BLG is unknown, though the crystal structure of bovine BLG is consistent with a role in vitamin A transport (1). We previously reported that mice carrying a sheep BLG transgene secrete BLG into their milk (2); BLG regulatory regions can direct expression of biomedical proteins into the milk of transgenic mice and sheep (3)(4)(5). In this context, it is important that transgene expression is stable. Unstable transgene expression has been described previously; Palmiter et al. (6) reported that the level of herpes simplex virus thymidine kinase expression could vary by more than an order of magnitude among progeny of the same founder. Although other transgene insertions express to variable degrees within individual cell lines or transgenic mouse lines (refs. 7-19; M. Mehtali and R.L., unpublished data), there has been no common explanation for the instability of expression. Unstable expression may be due to strong selection against the transgene, for instance by the failure of sperm fertility engendered by testicular thymidine kinase expression (7,8) or by the toxicity of high-level hepatic expression of plasminogen activator (9). A transgene inserted into the X chromosome (10) or an X-autosome translocation (20) generates mosaic expression due to stochastic X chromosome inactivation. Silencing has also been observed when the transgene integrates into repeat sequence or satellite DNA (11,12), whereas different levels of transgene expression between animals of the same lineage have been attributed to strain-specific modifier genes (13-15).Mosaic patterns of expression were also observed in transgenic animals bearing intestinal fatty-acid binding protein fusion transgenes (16). Here, mosaicism was attributed to a deficit of cis-acting elements in the tr...

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Section: Introductionmentioning

confidence: 99%

Variegated transgene expression in mouse mammary gland is determined by the transgene integration locus.

Dobie

Lee

Fantes

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

139

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Involvement of unstable chromosomal regions containing C-heterochromatin and fragile sites in the integration of amplifieddhfr domains

Riva

Morghen

Larizza

1989

Somat Cell Mol Genet

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A 10(-3) M methotrexate (MTX)-resistant variant (H2), selected from the murine fibrosarcoma line B77-3T3/AA12, was characterized after 5 (H2 MTXRes I) and 9 (H2 MTXRes II) months of in vitro propagation in the presence of the drug. Southern blot hybridization of wild-type and H2 MTXRes DNAs confirmed amplification of the dhfr gene without apparent rearrangements in its structure. Cytogenetic analysis revealed that double minutes (DMs) predominated in H2 MTXRes I, whereas homogeneously staining regions (HSRs) were the main feature of H2 MTXRes II cells. HSRs, shown to contain dhfr sequences by in situ chromosome hybridization, were localized within two rearranged chromosomes, designated as m1 and m2 because of their derivation from the marker chromosome m of AA12 cells. This chromosome, characterized by two interstitial C bands adjacent to two nonstaining gaps, was no longer observed in H2 MTXRes II cells. A role for nonrandom involvement of chromosome m in the integration of amplified DNA is suggested by the finding of another HSR-chromosome, m3, derived from m, in an independent MTXRes clone (B1). Rearrangement in one of the unstable C-band/gap regions of chromosome m is proposed as the unifying mechanism that may account for the outcome of the three HSR chromosomes observed.

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Effect of cis-located human satellite DNA on the electroporation efficiency of neo and HSV-1 tk containing plasmids

Fouquet

DuBow

1992

Mutation Research/Fundamental and Molecular Mechanisms of Mutag

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Satellite DNA induces unstable expression of the adjacent herpes simplex virus tk gene cotransfected in mouse cells.

Cited by 8 publications

References 38 publications

Variegated transgene expression in mouse mammary gland is determined by the transgene integration locus.

Variegated transgene expression in mouse mammary gland is determined by the transgene integration locus.

Involvement of unstable chromosomal regions containing C-heterochromatin and fragile sites in the integration of amplifieddhfr domains

Effect of cis-located human satellite DNA on the electroporation efficiency of neo and HSV-1 tk containing plasmids

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