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Journal of Virology, February 2008, p. 1622-1625, Vol. 82, No. 3
0022-538X/08/$08.00+0     doi:10.1128/JVI.02097-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Murine Endogenous Retrovirus MuERV-L Is the Progenitor of the "Orphan" Epsilon Viruslike Particles of the Early Mouse Embryo

David Ribet,^1, Sophie Louvet-Vallée,^2, Francis Harper,³ Nathalie de Parseval,^1, Marie Dewannieux,^1, Odile Heidmann,¹ Gérard Pierron,³ Bernard Maro,² and Thierry Heidmann^1*

Unité des Rétrovirus Endogènes et Éléments Rétroïdes des Eucaryotes Supérieurs, CNRS UMR 8122, Institut Gustave Roussy, Villejuif F-94805, and Université Paris-Sud, Orsay F-91405, France,¹ Laboratoire de Biologie Cellulaire du Développement, CNRS UMR 7622, Université Pierre et Marie Curie, Paris F-75252, France,² Laboratoire de Réplication de l'ADN et Ultrastructure du Noyau, UPR 1983 Institut André Lwoff, Villejuif F-94801, France³

Received 21 September 2007/ Accepted 13 November 2007

Viruslike particles which displayed a peculiar wheellike appearance that distinguished them from A-, B- or C-type particles had previously been described in the early mouse embryo. The maximum expression of these so-called epsilon particles was observed in two-cell-stage embryos, followed by their rapid decline at later stages of development and no particles detected at the zygote one-cell stage. Here, we show that these particles are in fact produced by a newly discovered murine endogenous retrovirus (ERV) belonging to the widespread family of mammalian ERV-L elements and named MuERV-L. Using antibodies that we raised against the Gag protein of these elements, Western blot analysis and in toto immunofluorescence studies of the embryos at various stages disclosed the same developmental expression profile as that observed for epsilon particles. Using expression vectors for cloned, full-length, entirely coding MuERV-L copies and cell transfection, direct identification of the epsilon particles was finally achieved by high-resolution electron microscopy.

Published ahead of print on 28 November 2007.

These authors contributed equally to this work.

Present address: INSERM, Département de la Recherche en Santé Publique, F-75654 Paris cedex 13, France.

Present address: Department of Immunology and Molecular Pathology, University College of London, Windeyer Institute, London W1T 4JF, United Kingdom.

This article has been cited by other articles:

• Ribet, D., Harper, F., Esnault, C., Pierron, G., Heidmann, T. (2008). The GLN Family of Murine Endogenous Retroviruses Contains an Element Competent for Infectious Viral Particle Formation. J. Virol. 82: 4413-4419 [Abstract] [Full Text]