Immunolocalization and developmental expression of dystrophin related protein in skeletal muscle.

Dystrophin Related Protein is the recently identified protein product of a large autosomal transcript, showing significant similarity to dystrophin at the carboxyl terminus. Dystrophin related protein and dystrophin share a similar abundance and molecular weight, however, they differ both in their tissue distribution and expression in Duchenne/Becker muscular dystrophy. Here we define the immunolocalization of dystrophin related protein to neuromuscular and myotendinous junctions, along with peripheral nerves and vasculature of skeletal muscle. Groups of regenerating muscle fibres as well as embryonic and neonatal muscle express far greater amounts of dystrophin related protein compared with adult mdx mice. These findings may explain the paradoxical labelling seen using dystrophin antibodies in Duchenne patients and dystrophin deficient mdx mice. Finally, no abnormalities of dystrophin related protein expression were detected in three patients with Duchenne-like autosomal recessive muscular dystrophy.