Murine endogenous retrovirus MuERV-L is the progenitor of the "orphan" epsilon viruslike particles of the early mouse embryo.
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.
Unité des Rétrovirus Endogènes et Eléments Rétroïdes des Eucaryotes Supérieurs, CNRS UMR 8122, Institut Gustave Roussy, 39 Rue Camille Desmoulins, F-94805 Villejuif, France.
David
D
Ribet
Sophie
S
Louvet-Vallée
Francis
F
Harper
Nathalie
N
de Parseval
Marie
M
Dewannieux
Odile
O
Heidmann
Gérard
G
Pierron
Bernard
B
Maro
Thierry
T
Heidmann
D000818:Animals; D015153:Blotting, Western; D004622:Embryo, Mammalian / Q000821:virology*; D020077:Endogenous Retroviruses / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D030283:Epsilonretrovirus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D051379:Mice; D014764:Viral Proteins / Q000276:immunology; D022701:Virosomes / Q000276:immunology / Q000302:isolation & purification*
D014764:Viral Proteins; D022701:Virosomes