Nestin is expressed during development and in myotendinous and neuromuscular junctions in wild type and desmin knock-out mice

Desmin, the main component of intermediate filaments (IFs) in mature skelet al muscle, forms an interlinking scaffold around myofibrils with connection s to the sarcolemma and the nuclear membrane. Desmin is enriched in neuromu scular and myotendinous junctions. Mice lacking the desmin gene develop nor mally and reproduce. However, postnatally they develop a cardiomyopathy and a dystrophy in highly used muscles. We have investigated whether and how n euromuscular and myotendinous junctions are affected and whether nestin com pensates for the lack of desmin in the knock-out (K/O) mice. We show that n either neuromuscular nor myotendinous junctions were markedly affected in t he desmin K/O mice. In neuromuscular junctions nestin was present between t he postjunctional folds and the subneural nuclei and between the nucleus an d the myofibrillar cytoskeleton. In myotendinous junctions nestin was prese nt between myofibrils at the Z-disc level and in longitudinal strands close to and at the junction. Nestin expression at these specialized sites, as w ell as during myogenesis and myofibrillogenesis, is independent of the pres ence of desmin. In desmin K/O mice nestin was also found in regenerating my ofibers. The presence of nestin at neuromuscular and myotendinous junctions might provide enough strength for preservation and organization of the jun ctional areas, although desmin is lacking, (C) 1999 Academic Press.