Syncytin-2 Explained

Syncytin-2 also known as endogenous retrovirus group FRD member 1 is a protein that in humans is encoded by the ERVFRD-1 gene.^[1] This protein plays a key role in the implantation of human embryos in the womb.^[2]

This gene is conserved among all primates, with an estimated age of 45 million years. The receptor for this fusogenic env protein is MFSD2. The mouse syncytins are not true orthologues.^[3]

The virus, along with some very similar insertions, belong to a group under the Gammaretrovirus-like class I ERVs. Similar ERVs are found in artiodactyls, a result of an independent integration event.^[4] A proposed nomenclature suggests putting all such "class I" elements in a genus-level taxon separate from Gammaretrovirus.^[5]

Further reading

• de Parseval N, Lazar V, Casella JF, Benit L, Heidmann T . Survey of human genes of retroviral origin: identification and transcriptome of the genes with coding capacity for complete envelope proteins . Journal of Virology . 77 . 19 . 10414–22 . October 2003 . 12970426 . 228468 . 10.1128/JVI.77.19.10414-10422.2003 .
• Blaise S, de Parseval N, Bénit L, Heidmann T . Genomewide screening for fusogenic human endogenous retrovirus envelopes identifies syncytin 2, a gene conserved on primate evolution . Proceedings of the National Academy of Sciences of the United States of America . 100 . 22 . 13013–8 . October 2003 . 14557543 . 240736 . 10.1073/pnas.2132646100 . 2003PNAS..10013013B . free .
• Blaise S, Ruggieri A, Dewannieux M, Cosset FL, Heidmann T . Identification of an envelope protein from the FRD family of human endogenous retroviruses (HERV-FRD) conferring infectivity and functional conservation among simians . Journal of Virology . 78 . 2 . 1050–4 . January 2004 . 14694139 . 368808 . 10.1128/JVI.78.2.1050-1054.2004 .
• Renard M, Varela PF, Letzelter C, Duquerroy S, Rey FA, Heidmann T . Crystal structure of a pivotal domain of human syncytin-2, a 40 million years old endogenous retrovirus fusogenic envelope gene captured by primates . Journal of Molecular Biology . 352 . 5 . 1029–34 . October 2005 . 16140326 . 10.1016/j.jmb.2005.07.058 .
• Malassiné A, Blaise S, Handschuh K, Lalucque H, Dupressoir A, Evain-Brion D, Heidmann T . Expression of the fusogenic HERV-FRD Env glycoprotein (syncytin 2) in human placenta is restricted to villous cytotrophoblastic cells . Placenta . 28 . 2–3 . 185–91 . 2007 . 16714059 . 10.1016/j.placenta.2006.03.001 .

Notes and References

1. Web site: Entrez Gene: HERV-FRD HERV-FRD provirus ancestral Env polyprotein.
2. Vargas A, Moreau J, Landry S, LeBellego F, Toufaily C, Rassart E, Lafond J, Barbeau B . Syncytin-2 plays an important role in the fusion of human trophoblast cells . Journal of Molecular Biology . 392 . 2 . 301–18 . 2009 . 19616006 . 10.1016/j.jmb.2009.07.025 .
3. Lavialle C, Cornelis G, Dupressoir A, Esnault C, Heidmann O, Vernochet C, Heidmann T . Paleovirology of 'syncytins', retroviral env genes exapted for a role in placentation . Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences . 368 . 1626 . 20120507 . September 2013 . 23938756 . 3758191 . 10.1098/rstb.2012.0507 .
4. Vargiu . L . Rodriguez-Tomé . P . Sperber . GO . Cadeddu . M . Grandi . N . Blikstad . V . Tramontano . E . Blomberg . J . Classification and characterization of human endogenous retroviruses; mosaic forms are common. . Retrovirology . 22 January 2016 . 13 . 7 . 10.1186/s12977-015-0232-y . 26800882 . 4724089 . free .
5. Gifford . RJ . Blomberg . J . Coffin . JM . Fan . H . Heidmann . T . Mayer . J . Stoye . J . Tristem . M . Johnson . WE . Nomenclature for endogenous retrovirus (ERV) loci. . Retrovirology . 28 August 2018 . 15 . 1 . 59 . 10.1186/s12977-018-0442-1 . 30153831. 6114882 . free .