First published online January 10, 2008
Journal of Cell Science 121, 205e (2008)
© The Company of Biologists Limited
Axon identity: a question of timing
During the development of multipolar neurons, many neurites extend from the cell body. A single neurite eventually differentiates to form the mature axon, and the remainder become dendrites – but how and when is the axon-to-be selected? Some studies suggest that the axonal neurite is chosen at the bipolar stage, from one of the two neurites that extend first from opposite poles of the cell body. However, there is also evidence for stochastic selection at a later stage, when more neurites have sprouted. Now, Carlos Dotti and colleagues (p. 178) show, in bipolar-stage neurons in situ, that only one of the first two neurites contains the tau-1 protein (an axonal marker). Using time-lapse microscopy of isolated neurons, they go on to show that, in most cases, one of the first two neurites develops into the axon. Moreover, polarised organisation of microtubules and membrane traffic at the bipolar stage promotes axonal growth at one of the two neurites, and severing the axon of a multipolar neuron causes axon formation at the opposite pole of the cell. These data shed light on the timing of key events in brain development.
Related articles in JCS:
- Pyramidal neuron polarity axis is defined at the bipolar stage
- Froylan Calderon de Anda, Annette Gärtner, Li-Huei Tsai, and Carlos G. Dotti
JCS 2008 121: 178-185.
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