Proteomic profiling of x-linked muscular dystrophy

Progressive x-linked muscular dystrophy represents the most commonly inherited neuromuscular disorder in humans. Although the disintegration of the dystrophin-associated glycoprotein complex triggers the initial pathogenesis of Duchenne muscular dystrophy, secondary alterations in metabolic pathways, cellular signaling and the regulation of ion homeostasis are probably crucial factors that cause end-stage fibre degeneration. The application of mass spectrometry-based proteomics for the global cataloguing of muscle biomarkers has recently been applied to the analysis of the mdx animal model of muscular dystrophy and the biochemical evaluation of experimental exon skipping therapy. The fluorescence difference in-gel electrophoretic analysis of normal versus mdx diaphragm muscle revealed changed expression levels of proteins involved in nucleotide metabolism, Ca 2+-handling, the cellular stress response and key bioenergetic processes. The swift up-regulation of small heat shock proteins, such as cvHsp, seems to form an integral part of the repair mechanisms in dystrophic fibres and may be exploitable as a new option to treat inherited muscle degeneration. Importantly, the mass spectrometry-based profiling of mdx muscle following the specific removal of exon 23 in the mutated dystrophin gene transcript showed a partial reversal of important secondary changes. Experimental exon skipping restored the expression of the dystrophin isoform Dp427, its associated glycoprotein beta-dystroglycan, neuronal nitric oxide synthase, calsequestrin, adenylate kinase and the muscle-specific stress protein cvHsp. In the future, a well defined set of signature molecules could be used to improve diagnosis, monitor disease progression, identify new therapeutic pathways, and validate the effects of novel drugs or experimental treatments such as gene therapy.