Résumé :
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Communication n° 269. The development and plasticity of the nervous and neuromuscular systems involve highly regulated steps. Neuronal growth and differentiation rely on growth cone progression, which involves microtubules and related regulatory proteins. Stathmin family phosphoproteins share the ability to sequester tubulin and participate in the control of microtubule dynamics. Their developmentally regulated expression and their specific intracellular localization in elongating processes suggest that they may regulate neuronal growth and differentiation by locally controlling microtubule assembly. To better understand the common vs specific properties of stathmin family proteins during neuronal differentiation, we characterized their expression profile and localization in primary neuron cultures, in particular in the growth cone during process elongation. Stathmin family proteins are strongly expressed during the first stages of differentiation, accumulated in the Golgi, and specifically targeted to the regions where microtubules are highly dynamic. They are accumulated in the central domain of the growth cone, associated with bundled microtubules, and also detected in the peripheral actin-rich region, with individual "exploratory" microtubules. We then investigated their expression and localization in situ, in the neuromuscular system. At birth, stathmin, SCG10 and SCLIP are detected in all neurons of the spinal cord, as well as in intramuscular nerves and neuromuscular junctions. This expression is maintained in the adult for stathmin, whereas it is dramatically reduced for SCG10 and SCLIP, which become restricted to preganglionic neurons of the lateral horn and some of the motoneurons of the ventral horn. These observations suggest a role of stathmin family proteins in the establishment of the neuromuscular system. Functional studies are now in progress to understand their role in motoneuron differentiation and outgrowth in culture.
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