Abstract:
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Communication n° 503 Muscular dystrophies often present a specificity of muscle involvement. For example, in Limb-girdle dystrophy 2A associated with mutations in gene encoding for calpain-3 protein, muscle weakness starts in Gluteus maximus and adductors, the neck muscles are relatively spared and facial muscles showed exceptionally a minor clinical involvement even in the late stage of the disease. Up to now, the factors implicated in this specificity of involvement are unknown but their identification could open the way to compensatory strategies for curing these diseases. In calpain-3 deficient (KO-C3) mice, the most affected muscles are the Deltoid, Psoas, Soleus, Glutueus whereas the Tibialis anterior muscle is relatively spared. We undertook studies to investigate whether the specificity of impairment could be related to 1) a differential capacity to regenerate and/or 2) a differential protein composition of myofibers. First, depending of the muscle origin of the cells , their abilities to form myotube in vitro reveals some variability. Flux cytometry analysis of muscle cells indicates that CD45, stem cell antigen-1 and CD34 expression patterns are similar between wild-type (wt) muscles described to be spared and involved in KO-C3 mice. To further characterize myogenic potency of the cells, we are now pursuing this study by investigating others factors. Second, proteomic analysis of cytosolic samples of wt and KO-C3 muscles was performed by 2-D electrophoresis method. Differential protein expression patterns were observed between wt muscles. Mass spectrometry analysis is in progress to identify these factors. Following the identification of factor(s) involved in specificity of muscle impairment, we will modulate their expression or activity in the affected muscles of KO-C3 mice to evaluate their potency to correct the phenotypic signs.
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