Syncytin is a captive retroviral envelope protein involved in human placental morphogenesis

Nature. 2000 Feb 17;403(6771):785-9. doi: 10.1038/35001608.


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.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Cell Fusion
  • Endogenous Retroviruses / genetics*
  • Gene Expression
  • Gene Products, env / genetics
  • Gene Products, env / physiology*
  • Genes, Viral
  • Giant Cells / metabolism
  • Green Fluorescent Proteins
  • HeLa Cells
  • Humans
  • Interleukin-12 / genetics
  • Interleukin-12 / metabolism
  • Luminescent Proteins / genetics
  • Molecular Sequence Data
  • Pregnancy Proteins / genetics
  • Pregnancy Proteins / physiology*
  • Proviruses / genetics
  • Sequence Homology, Amino Acid
  • Tissue Distribution
  • Transfection
  • Trophoblasts / metabolism
  • Tumor Cells, Cultured


  • Gene Products, env
  • Luminescent Proteins
  • Pregnancy Proteins
  • syncytin
  • Green Fluorescent Proteins
  • Interleukin-12

Associated data

  • GENBANK/AF208161