Short report
Human endogenous retrovirus-FRD envelope protein (syncytin 2) expression in normal and trisomy 21-affected placenta
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* Corresponding author: Danièle Evain-Brion daniele.evain-brion@univ-paris5.fr
1 INSERM, U767, 4 avenue de l'Observatoire 75006 Paris, France
2 Université Paris Descartes, Faculté des Sciences Pharmaceutiques et Biologiques, 4 avenue de l'Observatoire, 75006 Paris, France
3 CNRS, Paris, F-75006 France
4 Unité des Rétrovirus Endogènes et Eléments Rétroïdes des Eucaryotes Supérieurs UMR 8122 CNRS, Institut Gustave Roussy, 39 rue Camille Desmoulins, 94805 Villejuif, France
5 PremUP, Paris, France
Retrovirology 2008, 5:6 doi:10.1186/1742-4690-5-6
Published: 23 January 2008Abstract
Human trophoblast expresses two fusogenic retroviral envelope proteins, the widely studied syncytin 1, encoded by HERV-W and the recently characterized syncytin 2 encoded by HERV-FRD. Here we studied syncytin 2 in normal and Trisomy 21-affected placenta associated with abnormal trophoblast differentiation. Syncytin 2 immunolocalization was restricted throughout normal pregnancy to some villous cytotrophoblastic cells (CT). During the second trimester of pregnancy, syncytin 2 was immunolocalized in some cuboidal CT in T21 placentas, whereas in normal placentas it was observed in flat CT, extending into their cytoplasmic processes. In vitro, CT isolated from normal placenta fuse and differentiate into syncytiotrophoblast. At the same time, syncytin 2 transcript levels decreased significantly with syncytiotrophoblast formation. In contrast, CT isolated from T21-affected placentas fused and differentiated poorly and no variation in syncytin 2 transcript levels was observed. Syncytin 2 expression illustrates the abnormal trophoblast differentiation observed in placenta of fetal T21-affected pregnancies.