Axon selection: From a polarized cytoplasm to a migrating neuron.

The shape of a neuron supplies valuable clues as to its function. Neurons typically extend a single long, thin axon, which will transmit signals and several shorter and thicker dendrites, which will receive signals. The understanding of the means by which neurons acquire a polarized morphology is a fundamental issue in developmental neurobiology. The current view suggests that axon selection involves a stochastic mechanism. However, new data suggest that a polarized cytoplasm not only determines the position of neurite emergence, but also sets the conditions for morphological polarization. In vertebrates, neurons migrate before establishing their final morphology. Recent work shows that the polarized cytoplasm also determines how neurons migrate. Thus, neuronal migration might influence the processes by which neurons form an axon.