Isolation and characterization of an avian myogenic cell line.

Myogenic cell lines have proven extremely valuable for studying myogenesis in vitro. Although a number of mammalian muscle cell lines have been isolated, attempts to produce cell lines from other classes of animals have met with only limited success. We report here the isolation and characterization of seven avian myogenic cell lines (QM1-4 and QM6-8), derived from the quail fibrosarcoma cell line QT6. A differentiation incompetent QM cell derivative was also isolated (QM5DI). The major features of QM cell differentiation in vitro closely resemble those of their mammalian counterparts. Mononucleated QM cells replicate in medium containing high concentrations of serum components. Upon switching to medium containing low serum components, cells withdraw from the cell cycle and fuse to form elongated multinucleated myotubes. Cultures typically obtain fusion indices of 43-49%. Northern blot and immunoblot analyses demonstrate that each differentiated QM cell line expresses a wide variety of genes encoding muscle specific proteins: desmin, cardiac troponin T, skeletal troponin T, cardiac troponin C, skeletal troponin I, alpha-tropomyosin, muscle creatine kinase, myosin light chain 2, and a ventricular isoform of myosin heavy chain. While all QM lines analyzed to date express at least some myosin light chain 2, only one line, QM7, expresses this gene at high levels. Surprisingly, none of the QM lines reported here express any known form of alpha-actin. The absence of sarcomeric actin expression may explain the absence of myofibrils in QM myotubes. These novel features of muscle gene expression in QM cells may prove useful for studying the role of specific muscle proteins during myogenesis. More importantly, however, the isolation of QM cell lines indicates that it may be feasible to isolate other avian myogenic cell lines with general utility for the study of muscle development.