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What Makes An Axon An Axon?

Date:
November 19, 2008
Source:
Rockefeller University Press
Summary:
Inside every axon is a dendrite waiting to get out. Scientists converted mature axons into dendrites by banishing a protein crucial for neuron development. The results suggest that this transformation could occur after nerve cell damage.
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Inside every axon is a dendrite waiting to get out. Hedstrom et al. converted mature axons into dendrites by banishing a protein crucial for neuron development. The results suggest that this transformation could occur after nerve cell damage.

At the junction between the axon and the cell body is the axon initial segment (AIS), which sparks action potentials. Researchers also suspect that the AIS enables an axon to maintain its identity. Although scientists have teased out some of the molecular events that determine whether a neuron outgrowth will become an axon or a dendrite, they know little about what keeps these structures distinct.

In cultured neurons, Hedstrom et al. used RNAi to cut production of ankyrinG, a protein that helps spur formation of the AIS. Loss of ankyrinG caused the AIS to disappear. For example, sodium channels that normally crowd the AIS's plasma membrane dispersed. When ankyrinG was absent the erstwhile axons began to resemble dendrites, sprouting spines and developing excitatory synapses. Characteristic molecules from the cell body and dendrites, such as the microtubule polymerizing protein MAP2, also infiltrated the axons.

The AIS appears to serve as a filter that screens out dendritic proteins, Hedstrom et al. conclude. How the structure bars some proteins from the axon is still uncertain. Injuries and diseases can transform dendrites into axons. The findings raise the possibility that these insults could cause the reverse transformation by changing the amount of ankyrinG and altering the AIS.

Journal reference: Hedstrom, K.L., et al. 2008. J. Cell Biol. Nov. 17, 2008 doi:10.1083/jcb.200806112.


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The above story is based on materials provided by Rockefeller University Press. Note: Materials may be edited for content and length.


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Rockefeller University Press. "What Makes An Axon An Axon?." ScienceDaily. ScienceDaily, 19 November 2008. <www.sciencedaily.com/releases/2008/11/081110112055.htm>.
Rockefeller University Press. (2008, November 19). What Makes An Axon An Axon?. ScienceDaily. Retrieved April 26, 2015 from www.sciencedaily.com/releases/2008/11/081110112055.htm
Rockefeller University Press. "What Makes An Axon An Axon?." ScienceDaily. www.sciencedaily.com/releases/2008/11/081110112055.htm (accessed April 26, 2015).

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