Cell and Tissue Research

, Volume 357, Issue 1, pp 355–362 | Cite as

Syncytin-1 in differentiating human myoblasts: relationship to caveolin-3 and myogenin

  • Bolette Bjerregard
  • Iwona Ziomkiewicz
  • Alexander Schulz
  • Lars-Inge Larsson
Regular Article


Myoblasts fuse to form myotubes, which mature into skeletal muscle fibres. Recent studies indicate that an endogenous retroviral fusion gene, syncytin-1, is important for myoblast fusions in man. We have now expanded these data by examining the immunolocalization of syncytin in human myoblasts induced to fuse. Additionally, we have compared the localization of syncytin with the localization of caveolin-3 and of myogenin, which are also involved in myoblast fusion and maturation. Syncytin was localized to areas of the cell membrane and to filopodial structures connecting myoblasts to each other and to myotubes. Weaker staining was present over intracellular vesicles and tubules. Caveolin-3 was detected in the sarcolemma and in vesicles and tubules in a subset of myoblasts and myotubes. The strongest staining occurred in multinucleated myotubes. Wide-field fluorescence microscopy indicated a partial colocalization of syncytin and caveolin-3 in a subset of myoblasts. Super-resolution microscopy showed such colocalization to occur in the sarcolemma. Myogenin was restricted to nuclei of myoblasts and myotubes and the strongest staining occurred in multinucleated myotubes. Syncytin staining was observed in both myogenin-positive and myogenin-negative cells. Antisense treatment downmodulated syncytin-1 expression and inhibited myoblast cell fusions. Importantly, syncytin-1 antisense significantly decreased the frequency of multinucleated myotubes demonstrating that the treatment inhibited secondary myoblast fusions. Thus, syncytin is involved in human myoblast fusions and is localized in areas of contact between fusing cells. Moreover, syncytin and caveolin-3 might interact at the level of the sarcolemma.


Syncytin Caveolin-3 Myogenin Myoblast Fusion Human 


  1. Aagaard L, Bjerregaard B, Kjeldbjerg AL, Pedersen FS, Larsson LI, Rossi JJ (2012) Silencing of endogenous envelope genes in human choriocarcinoma cells shows that envPb1 is involved in heterotypic cell fusions. J Gen Virol 93:1696–1699PubMedCentralPubMedCrossRefGoogle Scholar
  2. Beer C, Andersen DS, Rojek A, Pedersen L (2005) Caveola-dependent endocytic entry of amphotropic murine leukemia virus. J Virol 79:10776–10787PubMedCentralPubMedCrossRefGoogle Scholar
  3. Bjerregaard B, Holck S, Christensen IJ, Larsson LI (2006) Syncytin is involved in breast cancer-endothelial cell fusions. Cell Mol Life Sci 63:1906–1911PubMedCrossRefGoogle Scholar
  4. Bjerregaard B, Talts JF, Larsson LI (2011) The endogenous envelope protein syncytin is involved in myoblast fusion. In: Larsson LI (ed) Cell fusions: regulation and control. Springer, Berlin, pp 267–275CrossRefGoogle Scholar
  5. Blaise S, de Parseval N, Bénit L, Heidmann T (2003) Genomewide screening for fusogenic human endogenous retrovirus envelopes identifies syncytin 2, a gene conserved on primate evolution. Proc Natl Acad Sci U S A 100:13013–13018PubMedCentralPubMedCrossRefGoogle Scholar
  6. Blond JL, Lavillette D, Cheynet V, Bouton O, Oriol G, Chapel-Fernandes S, Mandrand B, Mallet F, Cosset FL (2000) An envelope glycoprotein of the human endogenous retrovirus HERV-W is expressed in the human placenta and fuses cells expressing the type D mammalian retrovirus receptor. J Virol 74:3321–3329PubMedCentralPubMedCrossRefGoogle Scholar
  7. Bolte S, Cordelières FP (2006) A guided tour into subcellular colocalization analysis in light microscopy. J Microsc 224:213–232PubMedCrossRefGoogle Scholar
  8. Chen EH, Olson EN (2005) Unveiling the mechanisms of cell-cell fusion. Science 308:369–373PubMedCrossRefGoogle Scholar
  9. Davis HL, Whalen RG, Demeneix BA (1993) Direct gene transfer into skeletal muscle in vivo: factors affecting efficiency of transfer and stability of expression. Hum Gene Ther 4:151–159PubMedCrossRefGoogle Scholar
  10. Dupressoir A, Vernochet C, Bawa O, Harper F, Pierron G, Opolon P, Heidmann T (2009) Syncytin-A knockout mice demonstrate the critical role in placentation of a fusogenic, endogenous retrovirus-derived, envelope gene. Proc Natl Acad Sci U S A 106:12127–12132PubMedCentralPubMedCrossRefGoogle Scholar
  11. Dupressoir A, Lavialle C, Heidmann T (2012) From ancestral infectious retroviruses to bona fide cellular genes: role of the captured syncytins in placentation. Placenta 33:663–671PubMedCrossRefGoogle Scholar
  12. Frendo JL, Olivier D, Cheynet V, Blond JL, Bouton O, Vidaud M, Rabreau M, Evain-Brion D, Mallet F (2003) Direct involvement of HERV-W Env glycoprotein in human trophoblast cell fusion and differentiation. Mol Cell Biol 23:3566–3574PubMedCentralPubMedCrossRefGoogle Scholar
  13. Galbiati F, Volonte D, Engelman JA, Scherer PE, Lisanti MP (1999) Targeted down-regulation of caveolin-3 is sufficient to inhibit myotube formation in differentiating C2C12 myoblasts. Transient activation of p38 mitogen-activated protein kinase is required for induction of caveolin-3 expression and subsequent myotube formation. J Biol Chem 274:30315–30321PubMedCrossRefGoogle Scholar
  14. Gazzerro E, Sotgia F, Bruno C, Lisanti MP, Minetti C (2010) Caveolinopathies: from the biology of caveolin-3 to human diseases. Eur J Hum Genet 18:137–145PubMedCentralPubMedCrossRefGoogle Scholar
  15. Gullberg D (2003) Cell biology: the molecules that make muscle. Nature 424:138–140PubMedCrossRefGoogle Scholar
  16. Hansen CG, Nichols BJ (2010) Exploring the caves: cavins, caveolins and caveolae. Trends Cell Biol 20:177–186PubMedCrossRefGoogle Scholar
  17. Jansen KM, Pavlath GK (2008) Molecular control of mammalian myoblast fusion. Methods Mol Biol 475:115–133PubMedCrossRefGoogle Scholar
  18. Koch D, Westermann M, Kessels MM, Qualmann B (2012) Ultrastructural freeze-fracture immunolabeling identifies plasma membrane-localized syndapin II as a crucial factor in shaping caveolae. Histochem Cell Biol 138:215–230PubMedCrossRefGoogle Scholar
  19. Larsson LI (2004) Novel actions of tyrphostin AG 879: inhibition of RAF-1 and HER-2 expression combined with strong antitumor effects on breast cancer cells. Cell Mol Life Sci 61:2624–2631PubMedCrossRefGoogle Scholar
  20. Mi S, Lee X, Li X, Veldman GM, Finnerty H, Racie L, LaVallie E, Tang XY, Edouard P, Howes S, Keith JC Jr, McCoy JM (2000) Syncytin is a captive retroviral envelope protein involved in human placental morphogenesis. Nature 403:785–789PubMedCrossRefGoogle Scholar
  21. Parton RG, Way M, Zorzi N, Stang E (1997) Caveolin-3 associates with developing T-tubules during muscle differentiation. J Cell Biol 136:137–154PubMedCentralPubMedCrossRefGoogle Scholar
  22. Pavlath GK (2011) Current progress towards understanding mechanisms of myoblast fusion in mammals. In: Larsson LI (ed) Cell fusions: regulation and control. Springer, Berlin, pp 249–265CrossRefGoogle Scholar
  23. Quach NL, Biressi S, Reichardt LF, Keller C, Rando TA (2009) Focal adhesion kinase signaling regulates the expression of caveolin 3 and beta1 integrin, genes essential for normal myoblast fusion. Mol Biol Cell 20:3422–3435PubMedCentralPubMedCrossRefGoogle Scholar
  24. Richardson BE, Nowak SJ, Baylies MK (2008) Myoblast fusion in fly and vertebrates: new genes, new processes and new perspectives. Traffic 9:1050–1059PubMedCentralPubMedCrossRefGoogle Scholar
  25. Sabourin LA, Rudnicki MA (2000) The molecular regulation of myogenesis. Clin Genet 57:16–25PubMedCrossRefGoogle Scholar
  26. Schermelleh L, Heintzmann R, Leonhardt H (2010) A guide to super-resolution fluorescence microscopy. J Cell Biol 190:165–175PubMedCentralPubMedCrossRefGoogle Scholar
  27. Scriven DR, Klimek A, Asghari P, Bellve K, Moore ED (2005) Caveolin-3 is adjacent to a group of extradyadic ryanodine receptors. Biophys J 89:1893–1901PubMedCentralPubMedCrossRefGoogle Scholar
  28. Søe K, Andersen TL, Hobolt-Pedersen AS, Bjerregaard B, Larsson LI, Delaissé JM (2011) Involvement of human endogenous retroviral syncytin-1 in human osteoclast fusion. Bone 48:837–846PubMedCrossRefGoogle Scholar
  29. Strick R, Ackermann S, Langbein M, Swiatek J, Schubert SW, Hashemol-hosseini S, Koscheck T, Fasching PA, Schild RL, Beckmann MW, Strissel PL (2007) Proliferation and cell-cell fusion of endometrial carcinoma are induced by the human endogenous retroviral Syncytin-1 and regulated by TGF-beta. J Mol Med 85:23–38PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Bolette Bjerregard
    • 1
  • Iwona Ziomkiewicz
    • 2
  • Alexander Schulz
    • 2
  • Lars-Inge Larsson
    • 2
    • 3
  1. 1.SymphogenLyngbyDenmark
  2. 2.Center for Advanced Bioimaging, Section for Transport Biology, Department of Plant Biology and Environmental SciencesUniversity of CopenhagenCopenhagenDenmark
  3. 3.Department of PathologyCopenhagen University Hospital HvidovreCopenhagenDenmark

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