title: Morphological characterization of actively fusing L6 myoblasts.
abstract: We have characterized morphologically the surface of L6 myoblasts at the time of active cell fusion using transmission electron microscopy. Two subclones of the L6 line were used in these studies: the L6Cl55 line that fuses to form multinucleated syncytia and the NF44 non-fusing variant. Ultrastructural analysis revealed an electron-opaque material at localized points of cell-cell apposition in actively fusing L6Cl55 cells. This material may be transported by and secreted from smooth-surfaced cytoplasmic vesicles with an electron-dense core. In contrast to L6Cl55 cells, the electron-dense plaques were seen infrequently in cultures of the NF44 non-fusing variant. This previously unidentified substance may be associated with cell-cell recognition or adhesion, both necessary prerequisites for myoblast membrane fusion. Alternatively, the electron-dense plaques may be directly involved in the fusion event.
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002450:Cell Communication; D002454:Cell Differentiation; D002459:Cell Fusion; D002460:Cell Line; D002462:Cell Membrane / Q000648:ultrastructure; D008854:Microscopy, Electron; D024510:Muscle Development; D009132:Muscles / Q000502:physiology / Q000648:ultrastructure*; D051381:Rats; D013997:Time Factors