Embryology Research Today is a free monthly online journal that collates and summarizes the latest research about Embryology, including details on stem cells, reproduction, transplants, cloning.

Murine endogenous retrovirus MuERV-L is the progenitor of the "orphan" epsilon viruslike particles of the early mouse embryo.

Ribet D, Louvet-Vallée S, Harper F, de Parseval N, Dewannieux M, Heidmann O, Pierron G, Maro B, Heidmann T

Unité des Rétrovirus Endogènes et Eléments Rétroïdes des Eucaryotes Supérieurs, CNRS UMR 8122, Institut Gustave Roussy, 39 Rue Camille Desmoulins, F-94805 Villejuif, France.

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 18 January 2008 in J Virol, 82(3): 1622-5.
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