Résumé :
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Dysferlin gene mutations cause limb-girdle muscular dystrophy (LGMD) 2B and miyoshi myopathy. These muscular dystrophies are characterized by progressive muscle weakness. Dysferlin is known to play an essential role in skeletal muscle membrane repair, although its proper function and the underlying mechanism remain unclear. Mutations in the caveolin-3 (Cav-3) gene cause LGMD 1C. Cav-3 is a muscle specific form of the caveolin family. Cave-3 plays a role in the formation of the caveolae, flask-shaped invaginations of the plasma membrane. Caveolae are a special type of membrane rafts. Cav-3 interacts with dysferlin and regulates its plasma membrane expression and rate of endocytosis. Resealing defects of the sarcolemma in mouse models of caveolinopathy indicate an importance of cav-3 within the membrane repair mechanism. In this study we sought to characterize interacting partners of dysferlin within the membrane repair machinery and create a link to the formation of membrane rafts. Experiments were performed on human dysferlin- and caveolin-deficient cell lines. These cell lines were obtained from muscle biopsies of LGMD patients. Each cell line harbors different disease-causing mutation(s) leading to the total absence, miss-folding or miss-location of the dysferlin or cav-3 protein within the cell. The primary cell lines have been immortalized and characterized. To investigate the impact of dysferlin-deficiency on the structure of the sarcolemma, we apply electron microscopy on differentiated myotubes. Immunogold labeling of dysferlin, possible interacting partners within the membrane repair machinery and membrane raft markers will be done.
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