During mammalian brain development, many neurons migrate away from the site where they are born to settle in distant locations where they send out dendrites and axons to connect with other neurons. Both neuronal migration and axon/dendrite extension depend on forces generated by microtubule-based motor proteins such as cytoplasmic dynein. The effects of these forces depend, however, on the organization of the microtubule cytoskeleton. Rao et al. reveal that a small number of microtubules that aren’t attached to the centrosome, and which can therefore undergo motor-driven sliding, help migrating neurons navigate toward their destination and that, when the number of these centrosome-unattached microtubules is increased, neurons come to a halt and begin extending axon-like projections (1).

In migrating neurons, most, if not all, microtubules are attached to the centrosome. Many of them extend into a short leading process at the front...

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