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

Abstract

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.

Keywords

Syncytin Caveolin-3 Myogenin Myoblast Fusion Human 

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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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