Growth Associated Protein 43 (GAP-43), isolated from rat brain and considered a neuronal marker, is found involved in neurite branching, cytoskeleton remodelling, neuronal development and protection. However, GAP-43 mRNA or protein was found in embryonic chicken cells positive to meromyosin, as well as in human satellite cells, myoblasts and myotubes deriving from healthy or dystrophic muscles. Despite these evidences, there is no clear data about its localization or relationship with other muscle proteins.

The aim of our study was to investigate GAP-43 protein expression and localization in C2C12 cells and mice skeletal muscle fibres, using immunoblot and immunofluorescence protocols for confocal mycroscopy.

Immunoblot analyses showed the presence of the protein in C2C12 cell homogenates as well as in mature muscle fibers. Immunofluorescent images revealed that the protein was localized nearby the external nuclear membranes in C2C12 myoblasts, while in C2C12 myotubes, it was detected on muscular streaks, in a regular double strand pattern. This localization was found also in EDL fibres isolated from 1 week, 1 and 24 months old mice. In isolated adult mouse fibres, GAP-43 localization appeared in relationship with triadin, a-actinin, RyR, DHPR and mitochondria organization.

In conclusion, these preliminary data confirm the presence of GAP-43 in the skeletal muscle, and its localization support the hypothesis of a possible new functional role in the E-C coupling process.