Featured Research

from universities, journals, and other organizations

Both the rate and direction of axon growth in the spinal cord can be controlled

Date:
November 22, 2010
Source:
University of Southern California
Summary:
Both the rate and direction of axon growth in the spinal cord can be controlled, according to new research.

Axons (green) growing around one side of the developing spinal cord in the control (left) and in the experiment (right). In the experiment, by lowering the level of Limk1, the axons have now projected much further (yellow arrow) at the same stage in development.
Credit: Image courtesy of Samantha Butler.

Both the rate and direction of axon growth in the spinal cord can be controlled, according to new research by USC College's Samantha Butler and her collaborators.

The study by Butler; lead researcher Keith Phan and graduate students Virginia Hazen and Michele Frendo of USC College; and Zhengping Jia of the University of Toronto, was published online in the November 17 issue of the Journal of Neuroscience.

Butler, assistant professor of biological sciences, found that a series of connections at the cellular level produce a guidance cue that tells an axon how fast and in which direction to grow in an embryonic environment. Butler and her team also discovered that by modulating the activity of enzyme LIM domain kinase 1 (Limk1), the rate of axon growth can be stalled or accelerated.

Future applications of these findings may include enhancing the ability to regenerate neuronal circuits in patients suffering from spinal cord injuries or neurodegenerative diseases.

Initially, to understand these guidance cues, Butler and her colleagues studied the mechanisms by which neuronal circuits first develop in the embryonic states of rodents and chickens. While researching how an axon is programmed to grow in a particular direction, Butler and her group made a surprising discovery.

"We were expecting that when we perturbed the signaling pathway, the axon would be confused in terms of direction," Butler said. "But we found a much greater effect -- the axon grew at a different speed."

Under normal conditions, guidance cues cause a developing neuron to extend an axon into the environment. In a developing spinal cord, the cue comes in the form of a repellant, which acts from behind the cell body to direct the growth of the axon in the opposite direction. This repellant is mediated by bone morphogenetic proteins (BMPs).

In the beginning of the multi-step growth process, BMPs bind to a cell and activate its receptors; then a second messenger is triggered, in this case Limk1. Limk1 modifies the activity of a protein called cofilin. When cofilin is active, the axon grows. If the cofilin becomes inactive, growth comes to a halt.

Butler and her team discovered that by increasing the amount of cofilin, or decreasing the amount of the restricting Limk1, the commissural axon growth accelerated. Likewise, when the amount of cofilin was decreased, or the amount of Limk1 was increased, axon growth stopped.

The axon growth in embryonic spinal cords in which Limk1 was lowered appeared to be more advanced than in controls -- the axons grew up to 25 percent faster.

Since the axon is growing through an ever-changing environment, if the accelerated rate moves the axon to its subsequent signal destination too fast, that destination may not yet be created. As a result, growth acceleration can lead to errors in the process, Butler said. She hopes to determine the optimal rate of acceleration that prevents these errors but still supports enhanced regeneration.

"That the growth of axons needs to be controlled in time as well as space is something that is an interesting piece of biology," Butler said. "How it can be applied is very exciting."

Butler sees the application of this research as one part of the process for rebuilding damaged circuits in patients who have sustained spinal cord injuries, or those suffering from Parkinson's or Alzheimer's diseases, possibly using stem-cell-derived therapy. The average rate of axon growth is just 1 mm per day, so any increase would improve a patient's treatment.

"If we knew how to modulate cofilin to maximize the speed of axon growth," Butler said, "perhaps we could shave time off that process of circuit regeneration."


Story Source:

The above story is based on materials provided by University of Southern California. The original article was written by Laurie Moore. Note: Materials may be edited for content and length.


Journal Reference:

  1. K. D. Phan, V. M. Hazen, M. Frendo, Z. Jia, S. J. Butler. The Bone Morphogenetic Protein Roof Plate Chemorepellent Regulates the Rate of Commissural Axonal Growth. Journal of Neuroscience, 2010; 30 (46): 15430 DOI: 10.1523/JNEUROSCI.4117-10.2010

Cite This Page:

University of Southern California. "Both the rate and direction of axon growth in the spinal cord can be controlled." ScienceDaily. ScienceDaily, 22 November 2010. <www.sciencedaily.com/releases/2010/11/101122141047.htm>.
University of Southern California. (2010, November 22). Both the rate and direction of axon growth in the spinal cord can be controlled. ScienceDaily. Retrieved April 17, 2014 from www.sciencedaily.com/releases/2010/11/101122141047.htm
University of Southern California. "Both the rate and direction of axon growth in the spinal cord can be controlled." ScienceDaily. www.sciencedaily.com/releases/2010/11/101122141047.htm (accessed April 17, 2014).

Share This



More Health & Medicine News

Thursday, April 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Could Even Casual Marijuana Use Alter Your Brain?

Could Even Casual Marijuana Use Alter Your Brain?

Newsy (Apr. 16, 2014) A new study conducted by researchers at Northwestern and Harvard suggests even casual marijuana use can alter your brain. Video provided by Newsy
Powered by NewsLook.com
Thousands Of Vials Of SARS Virus Go Missing

Thousands Of Vials Of SARS Virus Go Missing

Newsy (Apr. 16, 2014) A research institute in Paris somehow misplaced more than 2,000 vials of the deadly SARS virus. Video provided by Newsy
Powered by NewsLook.com
Formerly Conjoined Twins Released From Dallas Hospital

Formerly Conjoined Twins Released From Dallas Hospital

Newsy (Apr. 16, 2014) Conjoined twins Emmett and Owen Ezell were separated by doctors in August. Now, nearly nine months later, they're being released from the hospital. Video provided by Newsy
Powered by NewsLook.com
Ebola Outbreak Now Linked To 121 Deaths

Ebola Outbreak Now Linked To 121 Deaths

Newsy (Apr. 15, 2014) The ebola virus outbreak in West Africa is now linked to 121 deaths. Health officials fear the virus will continue to spread in urban areas. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins