We have shown previously that actomyosin contractility plays an important role in controlling nuclear movements in future interneurons born in the medial ganglionic eminence (MGE) [Bellion et al.: J Neurosci 2005;25:5691-5699]. Because microtubules are known to control the structural and motile properties of migrating neurons, we asked whether alterations in the dynamic instability of microtubules would impair MGE cell migration. Migration was analyzed in flat cocultures in which green-fluorescent-protein-expressing MGE cells migrate on cortical cells from their explant of origin. A low (100 nM) concentration of nocodazole shortened the leading process of MGE cells that nevertheless continued to migrate at the same rate but frequently changed their direction of migration relative to control cells. MGE cells treated with a higher (1 muM) concentration of nocodazole that strongly destabilized microtubules took on multipolar morphology. They extended thin and labile processes. MGE cells no longer exhibited directional migration and migration velocity slowed 2-fold. These results suggest that microtubule stability is crucial for maintaining polarity and controlling the directional migration of MGE cells, whereas additional mechanisms are required to control cell motility.
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