Neuronal polarity: from extracellular signals to intracellular mechanisms

After they are born and differentiate, neurons break their previous symmetry, dramatically change their shape, and establish two structurally and functionally distinct compartments-axons and dendrites-within one cell. How do neurons develop their morphologically and molecularly distinct compartments? Recent studies have implicated several signalling pathways evoked by extracellular signals as having essential roles in a number of aspects of neuronal polarization.