Résumé :
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Nuclear movement during myofiber formation The formation of a myofiber requires the fusion of myoblasts to form a myotube which then differentiate into a mature myofiber. During all these steps, the position of the nuclei changes: during the formation of the myotube, the nuclei from myoblasts move from the site of fusion to the center of the myotube. During myofiber formation, the nuclei move from the center to the periphery of the myotube. Moreover, in the mature myofiber, some nuclei become anchored close to the clusters of acetylcholine receptors, precursor of neuromuscular synapse. It has been proposed that the distribution of nuclei in the mature myofiber forms distinct functional domains and this is probably important for muscle function since mis-distribution of nuclei is observed during muscle regeneration and in some muscular disorders. The question of how the position of nucleus is established in muscle cells and what are the molecular mechanisms responsible for the position of the nucleus in muscle cells has not been addressed. To answer this question we are identifying the nuclear position events that occur during myotube formation, using both primary and immortalized myoblasts. We are using high content time-lapse microscope to determined the trajectories of nuclei after cell fusion. Using this approach, we will identify the cytoskeleton elements involved in nuclear position (actin and microtubules). Furthermore, we will characterize the pathways that regulate these nuclear movement events.
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