UNFUSED C2C12 MOUSE SKELETAL-MUSCLE CELLS EXPRESS NEUROFILAMENT 140K PROTEIN

Expression of neurofilament 140K protein in C2C12 mouse skeletal muscl e cells was studied. Immunofluorescence and immunoblot analyses reveal ed that NF140K was expressed at the proliferative stage and was coloca lized with the muscle-specific intermediate protein desmin, As muscle cell differentiation proceeded, the number of NF140K-positive cells de creased whereas the number of cells expressing muscle-specific marker proteins such as sarcomeric myosin heavy chain and troponin-T increase d, Down-regulation of NF140K and upregulation of a myogenic regulatory gene, the myogenin gene, started simultaneously. In differentiated mu scle cell cultures, unfused cells residing between myotubes remained N F140K-positive, NF140K and desmin double-positive cells were also foun d in a primary culture of adult mouse skeletal muscle cells. The resul ts suggest that NF140K may be a unique marker for uncommitted myoblast s.