ScienceDaily (Nov. 19, 2008) — 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.

Story Source:

Adapted from materials provided by Rockefeller University Press, via EurekAlert!, a service of AAAS.

Related Stories

Autopilot Guides Proteins In Brain (Apr. 27, 2009) — Proteins go everywhere in the cell and do all sorts of work, but a fundamental question has eluded biologists: how do the proteins know where to go? A new study offers one ...  > read more

Turn Back, Wayward Axon: Coreceptors Work Together As 'Navigators' For A Growing Axon, Study Shows (Mar. 15, 2009) — To a growing axon, the protein RGMa is a "Wrong Way" sign, alerting it to head in another direction. As a new study shows, translating that signal into cellular action requires teamwork from two ...  > read more

Neurons Found To Be Similar To U.S. Electoral College (Sep. 15, 2009) — A study has found that certain neurons, at one level, operate a little like the US Electoral College. The findings provide evidence supporting the "two-layer integration model," which attempts to ...  > read more

Brain Works More Chaotically Than Previously Thought (Mar. 11, 2007) — The brain seems process information more chaotically than has long been assumed. The passing of information from neuron to neuron does not occur exclusively at the synapses, i.e. the junctions ...  > read more

Search ScienceDaily

Detecting Diabetes With Light