Expression of various isoforms of neural cell adhesive molecules and their highly polysialylated counterparts in diseased human muscles.

Antibodies directed against neural cell adhesive molecules (NCAM) and in particular a monoclonal antibody recognizing polysialylated isoforms, were used to characterize the expression of these molecules in normal and diseased human muscles. Normal subjects as well as patients with inflammatory, dystrophic and denervating diseases were examined. By immunohistochemistry the main observations were (1) satellite cells expressed the non-sialylated form of NCAMs; (2) regenerative fibers strikingly expressed NCAMs and their sialylated isoforms both on membranes and in the cytoplasm; (3) in denervated muscles, fibers in atrophic groups and some fibers in acute denervation expressed NCAMs on their membrane but not the highly sialylated form; (4) finally, some fibers in myotonic dystrophy and fibers with rimmed vacuoles also expressed NCAMs. Biochemical approaches, using enzymes such as endoglycosidase N and phosphatidylinositol phospholipase C combined with immunoblot analysis allowed visualization of the nature of the expressed isoforms. We have shown that non activated cells, i.e. satellite cells and denervated fibers do not express polysialylated NCAMs. This post-translational modification may be only observed in activated or regenerating fibers. This would parallel the sequence of NCAM expression occurring in normal myogenic pathways.