Endogenous retroviral syncytin: compilation of experimental research on syncytin and its possible role in normal and disturbed human placentogenesis

Mol Hum Reprod. 2004 Aug;10(8):581-8. doi: 10.1093/molehr/gah070. Epub 2004 Jun 4.


Placental syncytin was first described in the year 2000 as a fusogenic glycoprotein originally derived from a human endogenous retroviral envelope gene. Although the presence of stable integrated retroviral elements within the human genome has been known for many years, their biological significance is still obscure and has usually been designated as irrelevant or even harmful. Syncytin, however, demonstrates tissue-specific expression and distinctive receptor interaction during trophoblast cell differentiation and syncytium formation. These findings indicate an involvement of syncytin in the development of the human placenta. Disturbances in placental architecture leading to severe placental dysfunction, such as pre-eclampsia, may therefore be discussed as a consequence of an altered syncytin system. We evaluate the hypothesis that syncytin is essential for human placenta formation and may also have played an important role in human placental evolution.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Transport System ASC / metabolism
  • Biological Evolution
  • Cell Differentiation
  • Endogenous Retroviruses / genetics
  • Endogenous Retroviruses / metabolism*
  • Female
  • Gene Products, env / genetics
  • Gene Products, env / metabolism*
  • Gestational Age
  • Humans
  • Immune Tolerance
  • Minor Histocompatibility Antigens
  • Placenta / chemistry
  • Placentation*
  • Pregnancy
  • Pregnancy Proteins / genetics
  • Pregnancy Proteins / metabolism*


  • Amino Acid Transport System ASC
  • Gene Products, env
  • Minor Histocompatibility Antigens
  • Pregnancy Proteins
  • SLC1A5 protein, human
  • syncytin