Abstract:
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Communication n° 164. Introduction : The absence of dystrophin protein leads to different phenotypes in different species, despite complete loss of dystrophin in all muscles. Patients affected by Duchenne Muscular Dystrophy show chronic degeneration/regeneration with progressive muscle wasting and an early death. Differently the mdx mouse initially shows normal muscle, with widespread skeletal muscle necrosis at the age of 3-4 weeks, followed by "successful" muscle fiber regeneration. Objectives : We hypothesized that comparison of 60,000-gene profiles in human DMD muscle (U95 GeneChip series and custom Affymetrix MuscleChip), and 36,000 gene profiles in mdx and experimental muscle regeneration (U74 GeneChip series) would identify differentially expressed genes as potential candidates for conferring protection to murine dystrophin deficient muscle. Methods : Expression profiling was performed using Affymetrix Chips U95 and U74 and data were analyzed using Microarray Suite version 4.0 (U95 A,B,C,D,E) and version 5.0 (U74 series). Confirmation of the expression profiling was performed through immunoistochemistry and immunoblotting, using custom-made antibodies. Results : we found different genes highly up-regulated in mdx mouse and in an experimental model of muscle regeneration, without any change in the DMD profiles. Custom-made antibodies confirmed the differential expression of the protein between the two species, showing a prevalent localization of the proteins at the myotendinous junction (MTJ) Conclusions : our data raise the hypothesis that the proteins, coded by the upregulated genes, could have a role in the better histopathological, thus clinical recovery of the mouse model. In particular remodeling at the MTJ and tendon could be a major player, since this sites are involved in the transmission of the contractile force generated by the myofibers to the bone. The MTJ is, indeed, a very dynamic site where two distinct lineages and tissues, tendon and muscle, form very specific yet strong interactions. We conclude that our approach enriched for components of the MTJ that are strongly up-regulated during muscle regeneration. Remodeling of the MTJ is likely an understudied aspect of neuromuscular disease, and may play a key role in the contractures seen in DMD.
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