title: Syncytin is a captive retroviral envelope protein involved in human placental morphogenesis.
abstract: Many mammalian viruses have acquired genes from their hosts during their evolution. The rationale for these acquisitions is usually quite clear: the captured genes are subverted to provide a selective advantage to the virus. Here we describe the opposite situation, where a viral gene has been sequestered to serve an important function in the physiology of a mammalian host. This gene, encoding a protein that we have called syncytin, is the envelope gene of a recently identified human endogenous defective retrovirus, HERV-W. We find that the major sites of syncytin expression are placental syncytiotrophoblasts, multinucleated cells that originate from fetal trophoblasts. We show that expression of recombinant syncytin in a wide variety of cell types induces the formation of giant syncytia, and that fusion of a human trophoblastic cell line expressing endogenous syncytin can be inhibited by an anti-syncytin antiserum. Our data indicate that syncytin may mediate placental cytotrophoblast fusion in vivo, and thus may be important in human placental morphogenesis.
authors.affiliation: Genetics Institute, Inc., Cambridge, Massachusetts 02140, USA.
authors.forename: S
authors.initials: S
authors.lastname: Mi
authors.forename: X
authors.initials: X
authors.lastname: Lee
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: G M
authors.initials: GM
authors.lastname: Veldman
authors.forename: H
authors.initials: H
authors.lastname: Finnerty
authors.forename: L
authors.initials: L
authors.lastname: Racie
authors.forename: E
authors.initials: E
authors.lastname: LaVallie
authors.forename: X Y
authors.initials: XY
authors.lastname: Tang
authors.forename: P
authors.initials: P
authors.lastname: Edouard
authors.forename: S
authors.initials: S
authors.lastname: Howes
authors.forename: J C
authors.initials: JC
authors.lastname: Keith
authors.forename: J M
authors.initials: JM
authors.lastname: McCoy
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002459:Cell Fusion; D020077:Endogenous Retroviruses / Q000235:genetics*; D015870:Gene Expression; D015686:Gene Products, env / Q000235:genetics / Q000502:physiology*; D005814:Genes, Viral; D015726:Giant Cells / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D018664:Interleukin-12 / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D011257:Pregnancy Proteins / Q000235:genetics / Q000502:physiology*; D011533:Proviruses / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014162:Transfection; D014327:Trophoblasts / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D015686:Gene Products, env; D008164:Luminescent Proteins; D011257:Pregnancy Proteins; C405335:syncytin; D049452:Green Fluorescent Proteins; D018664:Interleukin-12