Abstract
Phenotypic variation in mammals is frequently attributed to the action of quantitative trait loci (QTL) or the environment, but may also be epigenetic in origin. Here we consider a mechanism for phenotypic variation based on interference of transcription by somatically active retrotransposons. Transcriptionally competent retrotransposons may number in the tens of thousands in mammalian genomes. We propose that silencing of retrotransposons occurs by cosuppression during early embryogenesis, but that this process is imperfect and produces a mosaic pattern of retrotransposon expression in somatic cells. Transcriptional interference by active retrotransposons perturbs expression of neighboring genes in somatic cells, in a mosaic pattern corresponding to activity of each retrotransposon. The epigenotype of retrotransposon activity is reset in each generation, but incomplete resetting can lead to heritable epigenetic effects. The stochastic nature of retrotransposon activity, and the very large number of genes that may be affected, produce subtle phenotypic variations even between genetically identical individuals, which may affect disease risk and be heritable in a non-mendelian fashion.
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References
Risch, N.J. Searching for genetic determinants in the new millennium. Nature 405, 847–856 (2000).
Falconer, D.S. Introduction to Quantitative Genetics 438 (Longman Scientific & Technical, Essex, 1989).
Gartner, K. A third component causing random variability beside environment and genotype. A reason for the limited success of a 30 year long effort to standardize laboratory animals? Lab. Anim. 24, 71–77 (1990).
Gruneberg, H. Is there a viral component in the genetic background? Nature 225, 39–41 (1970).
Perry, W.L., Copeland, N.G. & Jenkins, N.A. The molecular basis for dominant yellow agouti coat color mutations. Bioessays 16, 705–707 (1994).
Vasicek, T.J. et al. Two dominant mutations in the mouse fused gene are the result of transposon insertions. Genetics 147, 777–786 (1997).
Hummel, K.P. The inheritance and expression of disorganization, an unusual mutation in the mouse. J. Exp. Zool. 137, 389–423 (1958).
Essien, F.B., Haviland, M.B. & Naidoff, A.E. Expression of a new mutation (Axd) causing axial defects in mice correlates with maternal phenotype and age. Teratology 42, 183–194 (1990).
Machin, G.A. Some causes of genotypic and phenotypic discordance in monozygotic twin pairs. Am. J. Med. Genet. 61, 216–228 (1996).
Martin, N., Boomsma, D. & Machin, G. A twin-pronged attack on complex traits. Nature Genet. 17, 387–392 (1997).
Bouchard, T.J., Jr., Lykken, D.T., McGue, M., Segal, N.L. & Tellegen, A. Sources of human psychological differences: the Minnesota Study of Twins Reared Apart. Science 250, 223–228 (1990).
Gartner, K. & Baunack, E. Is the similarity of monozygotic twins due to genetic factors alone? Nature 292, 646–647 (1981).
Jablonka, E. & Lamb, M.J. Epigenetic Inheritance and Evolution: The Lamarckian Dimension 346 (Oxford University Press, Oxford, 1995).
Holliday, R. The inheritance of epigenetic defects. Science 238, 163–170 (1987).
Wolffe, A.P. & Matzke, M.A. Epigenetics: regulation through repression. Science 286, 481–486 (1999).
Martienssen, R.A. & Richards, E.J. DNA methylation in eukaryotes. Curr. Opin. Genet. Dev. 5, 234–242 (1995).
Cavalli, G. & Paro, R. The Drosophila Fab-7 chromosomal element conveys epigenetic inheritance during mitosis and meiosis. Cell 93, 505–518 (1998).
Grewal, S.I. & Klar, A.J. Chromosomal inheritance of epigenetic states in fission yeast during mitosis and meiosis. Cell 86, 95–101 (1996).
Hollick, J.B., Dorweiler, J.E. & Chandler, V.L. Paramutation and related allelic interactions. Trends Genet. 13, 302–308 (1997).
Morgan, H.D., Sutherland, H.G., Martin, D.I. & Whitelaw, E. Epigenetic inheritance at the agouti locus in the mouse. Nature Genet. 23, 314–318 (1999).
Michaud, E.J. et al. Differential expression of a new dominant agouti allele (Aiapy) is correlated with methylation state and is influenced by parental lineage. Genes Dev. 8, 1463–1472 (1994).
Smit, A.F. Interspersed repeats and other mementos of transposable elements in mammalian genomes. Curr. Opin. Genet. Dev. 9, 657–663 (1999).
SanMiguel, P., Gaut, B.S., Tikhonov, A., Nakajima, Y. & Bennetzen, J.L. The paleontology of intergene retrotransposons of maize. Nature Genet. 20, 43–45 (1998).
Wilkinson, D.A., Mager, D.L. & Leong, J.C. Endogenous human retroviruses. in The Retroviridae (ed. Levy, J.A.) 465–535 (Plenum, New York, 1994).
Kazazian, H.H., Jr. Mobile elements and disease. Curr. Opin. Genet. Dev. 8, 343–350 (1998).
Fincham, J.R. & Sastry, G.R. Controlling elements in maize. Annu. Rev. Genet. 8, 15–50 (1974).
Kidwell, M.G. & Lisch, D. Transposable elements as sources of variation in animals and plants. Proc. Natl. Acad. Sci. USA 94, 7704–7711 (1997).
Emerman, M. & Temin, H.M. Genes with promoters in retrovirus vectors can be independently suppressed by an epigenetic mechanism. Cell 39, 449–467 (1984).
Corbin, V. & Maniatis, T. Role of transcriptional interference in the Drosophila melanogaster Adh promoter switch. Nature 337, 279–282 (1989).
Proudfoot, N.J. Transcriptional interference and termination between duplicated α-globin gene constructs suggests a novel mechanism for gene regulation. Nature 322, 562–565 (1986).
Parkhurst, S.M. & Corces, V.G. Interactions among the gypsy transposable element and the yellow and the suppressor of hairy-wing loci in Drosophila melanogaster. Mol. Cell. Biol. 6, 47–53 (1986).
Olson, E.N., Arnold, H.H., Rigby, P.W. & Wold, B.J. Know your neighbors: three phenotypes in null mutants of the myogenic bHLH gene MRF4. Cell 85, 1–4 (1996).
Fiering, S. et al. Targeted deletion of 5′HS2 of the murine β-globin LCR reveals that it is not essential for proper regulation of the β-globin locus. Genes Dev. 9, 2203–2213 (1995).
Mohn, A.R., Gainetdinov, R.R., Caron, M.G. & Koller, B.H. Mice with reduced NMDA receptor expression display behaviors related to schizophrenia. Cell 98, 427–436 (1999).
McClintock, B. The states of a gene locus in maize. Carnegie Institute of Washington Yearbook 66, 20–28 (1968).
Martienssen, R. & Baron, A. Coordinate suppression of mutations caused by Robertson's mutator transposons in maize. Genetics 136, 1157–1170 (1994).
Speek, M. Antisense promoter of human L1 retrotransposon drives transcription of adjacent cellular genes. Mol. Cell. Biol. 21, 1973–1985 (2001).
Krieg, A.M., Gourley, M.F. & Perl, A. Endogenous retroviruses: potential etiologic agents in autoimmunity. FASEB J. 6, 2537–2544 (1992).
Roemer, I., Reik, W., Dean, W. & Klose, J. Epigenetic inheritance in the mouse. Curr. Biol. 7, 277–280 (1997).
Yoder, J.A., Walsh, C.P. & Bestor, T.H. Cytosine methylation and the ecology of intragenomic parasites. Trends Genet. 13, 335–340 (1997).
Monk, M., Boubelik, M. & Lehnert, S. Temporal and regional changes in DNA methylation in the embryonic, extraembryonic and germ cell lineages during mouse embryo development. Development 99, 371–382 (1987).
Kafri, T. et al. Developmental pattern of gene-specific DNA methylation in the mouse embryo and germ line. Genes Dev. 6, 705–714 (1992).
Piko, L., Hammons, M.D. & Taylor, K.D. Amounts, synthesis, and some properties of intracisternal A particle-related RNA in early mouse embryos. Proc. Natl. Acad. Sci. USA 81, 488–492 (1984).
Packer, A.I., Manova, K. & Bachvarova, R.F. A discrete LINE-1 transcript in mouse blastocysts. Dev. Biol. 157, 281–283 (1993).
Fire, A. RNA-triggered gene silencing. Trends Genet. 15, 358–363 (1999).
Jones, L. et al. RNA-DNA interactions and DNA methylation in post-transcriptional gene silencing. Plant Cell 11, 2291–2302 (1999).
Tabara, H. et al. The rde-1 gene, RNA interference, and transposon silencing in C. elegans. Cell 99, 123–132 (1999).
Ketting, R.F. & Plasterk, R.H. A genetic link between co-suppression and RNA interference in C. elegans. Nature 404, 296–298 (2000).
Chaboissier, M.C., Bucheton, A. & Finnegan, D.J. Copy number control of a transposable element, the I factor, a LINE-like element in Drosophila. Proc. Natl. Acad. Sci. USA 95, 11781–11785 (1998).
Jensen, S., Gassama, M.P. & Heidmann, T. Taming of transposable elements by homology-dependent gene silencing. Nature Genet. 21, 209–212 (1999).
Baylin, S.B. & Herman, J.G. DNA hypermethylation in tumorigenesis: epigenetics joins genetics. Trends Genet. 16, 168–174 (2000).
Lyle, R. et al. The imprinted antisense RNA at the Igf2r locus overlaps but does not imprint Mas1. Nature Genet. 25, 19–21 (2000).
Acknowledgements
We thank R. Stöger, H. Morgan, B. Graham, G. Thomson, M. Kappelman and J. Cropley for helpful discussions.
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Whitelaw, E., Martin, D. Retrotransposons as epigenetic mediators of phenotypic variation in mammals. Nat Genet 27, 361–365 (2001). https://doi.org/10.1038/86850
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DOI: https://doi.org/10.1038/86850