Syncytin is a captive retroviral envelope protein involved in human placental morphogenesis.
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.
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Genetics Institute, Inc., Cambridge, Massachusetts 02140, USA.
Lee
X
X
Li
X
X
Veldman
G M
GM
Finnerty
H
H
Racie
L
L
LaVallie
E
E
Tang
X Y
XY
Edouard
P
P
Howes
S
S
Keith
J C
JC
McCoy
J M
JM
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
D015686:Gene Products, env; D008164:Luminescent Proteins; D011257:Pregnancy Proteins; C405335:syncytin; D049452:Green Fluorescent Proteins; D018664:Interleukin-12