Neurons take shape.

To construct the intricate network of connections that supports the functions of an adult nervous system, neurons must form highly elaborate processes, extending in the appropriate direction across long distances to form synapses with their partners. As the nervous system takes shape, the process of neuronal morphogenesis is controlled by a broad repertoire of cellular signals. These extracellular cues and cellular interactions are translated by receptors at the cell surface into physical forces that control the dynamic architecture of the neuron as it explores the surrounding terrain. The interpretation of these cues involves a large set of intracellular proteins, whose functional logic we are just beginning to appreciate. We shall consider the basic mechanics of neuronal morphogenesis and some of the emerging pathways that seem to link the outer and inner worlds of the neuron.