Building Brains by unknow

Author:unknow
Language: eng
Format: epub
Publisher: John Wiley & Sons, Incorporated
Published: 2017-11-20T00:00:00+00:00

6.7.2 Ensuring there is just one axon

In cultured hippocampal cells, only a single neurite becomes the axon, the remainder later becoming dendrites. If this axon is cut off, then another neurite can differentiate to take its place (Figure 6.15). This gives a clue as to how neurons become polarized to produce just one axon. A plausible model to explain this observation is that all the neurites compete for a limited amount of growth‐permitting molecules produced in the cell body (such as PIP3 and PAR complex). One neurite wins this competition to become the axon, which then extends rapidly. If the axon is removed, then the remaining neurites can compete once more for these molecules. Both PIP3 and PAR complex are known to be transported as cargoes to the growing tip of the axon (Figure 6.12). This model also suggests how microtubule stabilization leads to axon specification and rapid extension: it may enhance the transport of these signalling components into the neurite, allowing it to monopolize the cellular pool.9

Figure 6.15 Specifying a single axon. If the axon of a cultured hippocampal neuron is cut, a second neurite elongates to form a replacement axon.

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