Fibroblasts Fuse with Myotubes Developing in Culture
Skeletal muscle cells are formed during development in vivo as well as in vitro by the fusion of mononucleate, undifferentiated precursors, termed myoblasts. Over the last year, we have observed that, although rarely, fibroblasts also are able to fuse with developing myotubes in tissue culture (Chaudhari et al., 1989). The experiments which we present here were carried out primarily on muscle cells from the muscular dysgenesis (mdg) strain of mice (Pai, 1965). This strain carries a mutation in the gene for a skeletal muscle specific calcium channel (Tanabe et al. 1988), rendering skeletal muscle totally paralyzed. When dysgenic myoblasts fuse in culture, these myotubes are unable to twitch, either spontaneously or in response to electrical stimulation. However, dysgenic myotubes can be induced to regain twitch responses by the introduction of either a normal myoblast nucleus (Peterson and Pena, 1984) or a normal gene to replace the altered calcium channel (Tanabe et. al. 1988). Thus, dysgenic myotubes allowed us to visualize (through their altered phenotype), rare events: the incorporation of single, normal, fibroblast nuclei.
KeywordsNormal Fibroblast Mouse Myoblast Fibroblast Type Fibroblast Nucleus Punctate Fluorescence
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