Construction of a polarized neuron


  • This review was presented at The Journal of Physiology Symposium entitled Size Matters: Formation and Function of GIANT Synapses, which took place at the Annual Meeting of the Society for Neuroscience, New Orleans, LA, USA, on 12 October 2012. It was commissioned by the Editorial Board and reflects the views of the authors.

G. A. Spirou: Center for Neuroscience, West Virginia University School of Medicine, One Medical Center Drive, Morgantown, WV 26506-9303, USA.  Email:


Abstract  Aside from rare counterexamples (e.g. the starburst amacrine cell in retina), neurons are polarized into two compartments, dendrites and axon, which are linked at the cell body. This structural polarization carries an underlying molecular definition and maps into a general functional polarization whereby inputs are collected by the dendrites and cell body, and output is distributed via the axon. Explanations of how the polarized structure arises invariably coalesce around somatic polarity, defined by the roving location of the microtubule organizing centre, or centrosome, the Golgi apparatus, associated endosomes and the nucleus during early development. In some neurons, proper positioning of these structures can determine the sites for axon and dendrite elongation, and support processes that underlie cell migration. We briefly review these events as a basis to propose a new role for polarized arrangement of somatic organelles as a potential determinant for patterned innervation of the cell body membrane. We cite an example from preliminary studies of synaptogenesis at the calyx of Held, a large nerve terminal that selectively innervates the cell body of its postsynaptic partner, and suggest other neural systems in which polarity mechanisms may guide initial synapse formation onto the somatic surface.