Résumé :
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Desminopathy is a clinically and genetically heterogeneous group of sporadic and familial skeletal and cardiac muscular disorders with a common morphological phenotype (Goldfarb et al., 2004; Paulin et al., 2004). Little is known about the pathogenesis of desminopathy. Currently, more than forty different mutations have been identified in desmin gene as responsable for desminopathy. Desmin is a major intermediate filament protein of muscle cells. It is one of the earliest muscle-specific proteins. Although the expression of mutated desmin gene occurs during early stages of embryogenesis in muscle cells, myopathies develop as early as in adolescence or later in adulthood. Nevertheless, it is possible that disturbances occuring during early state of myogenesis gradually lead to some symptoms of desminopathy. Following this, our team is interested in decrypting the early event occurring during the establishment of desminopathy. The aim of this study is to correlate the perturbations of myogenesis induced by different desmin mutations (R406W and I451M) with several cellular and molecular parameters. To conduct this, we use stably transfected C2C12 myoblast cell lines with a construction consisting of the human cDNA desmin sequence under the control of the desmin promoter. After amplification of each selected clone expressing wild-type, R406W or I451M desmin, we first examined their capacities of adhesion, proliferation, fusion and differentiation. We found that the cells which express human wild-type desmin or I451M desmin mutants actively proliferate, fuse and differentiate to form multinucleated myotubes in culture, which indicates that myogenic potential is not impaired. In contrast, the cells expressing R406W desmin mutant are characterized by small size and round shape. In addition, during the first days of culture, a lot of cells were weakly attached to cell culture surface. Several markers of differentiation were quantified by a combination of qPCR and western-blot which confirm impaired myogenic differentiation of cells expressing R406W desmin mutant. To confirm our results in a more in vivo context, injections of the cell lines under the dorsal skin of C57BL/6 mice were performed. Taken together, these results underline that R406W mutation may consequently alter the myogenic program by disturbing cell attachment and interaction with sarcolemmal proteins.
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