The role of the fibroblast growth factor receptor in skeletal myogenesis
Skeletal muscle development can be modeled using primary myocytes or established myocyte lines. These in vitro models have been used to study regulatory events of myogenesis. Early studies demonstrated that fibroblast growth factors promote proliferation and prevent differentiation of skeletal myocytes. FGFs and FGF receptors are both downregulated with myocyte differentiation. Studies have demonstrated that endogenous FGFs regulate myogenesis. The influence of FGFs was believed to be mediated through high affinity receptor tyrosine kinases. However, some studies demonstrating a role for nuclear localized FGF, challenged this belief. Furthermore, the two best characterized FGFs lack signal sequences making unclear whether they needed to exit the cell in order to exert their effects. In order to determine whether endogenous FGFs exit the cell to regulate myogenesis and, if so, whether high affinity tyrosine kinase receptors mediate the myogenic response of FGFs, two approaches were used. The first approach, stably expressing a dominant negative FGFR-1 in skeletal myocytes, was used to determine if decreasing receptor availability decreases proliferation and/or promotes differentiation. The second approach was to make myocyte lines that constitutively express the wild type FGF receptor-1. These cells were used to determine whether increasing signaling through the FGF receptor increases proliferation and/or delays differentiation. The ability of these cells to proliferate was measured by cell counting and enzymatic activity of muscle specific creatine kinase was measured as a marker of differentiation. Myocytes expressing the dominant negative receptor proliferated more slowly and differentiated more quickly than control cells. Conversely, the myocytes constitutively expressing the wild type receptor proliferated more quickly and differentiated more slowly than control cells. These results demonstrate that endogenously produced FGFs use a transmembrane mediated signaling pathway to exert their effects and that the FGFR plays a regulatory role in myogenesis.
Scata, Kimberly Ann, "The role of the fibroblast growth factor receptor in skeletal myogenesis" (1996). Dissertations available from ProQuest. AAI9636213.