Navigation Links
Cerebral navigation: How do nerve fibers know what direction to grow in?

Nervous system development requires billions of neurons to migrate to the appropriate locations in the brain and grow nerve fibers (axons) that connect to other nerve cells in an intricate network. Growth cones, structures in the tips of growing axons, are responsible for steering axons in the right direction, guided by a complex set of signals from cells they encounter along the way. Some signals lure the axons to extend and grow in a particular direction; others are inhibitory, making the axon turn away or stop growing.

In two papers in the April 21 Neuron, researchers from Children's Hospital Boston reveal important insights into how inhibitory cues affect the growth cone, and identify possible targets within axons that could be blocked to overcome this inhibition. Such intervention could possibly enable damaged axons to regenerate (normally impossible in a mature nervous system) and ultimately restore nerve function.

It's been known that cells synthesize an inhibitory protein called ephrin, which binds to a receptor called Eph on the axon's growth cone. But how this triggers the axon to change course or stop growing has been a mystery.

"Very little has been known about the inner workings of the cell that govern axon guidance," says Michael Greenberg, PhD, Director of the Neurobiology Program at Children's and senior author on both studies. "These studies begin to give insight into how the various steps of axon guidance are controlled."

The first paper found that when ephrin binds to Eph receptors on the axon, it activates a protein called Vav2 in the cell's growth cone. Activation of Vav2 induces the cell to engulf the ephrin-Eph complex, breaking the bond between the two and repelling the axon, causing it to turn away. When mice were genetically modified to lack Vav2 and the related Vav3, thereby eliminating this repellent signal, the mice had abnormal axon projections and defects in neural circuitry formation.

The second paper demonstrates the role of a protein called ephexin1 in axon guidance. By itself, ephexin 1 promotes axon growth; neurons from mice genetically modified to lack ephexin1 had significantly shorter axons. But when ephrin is present and binds to Eph receptors, ephexin1 is chemically modified, causing it to alter the cell's cytoskeleton, or internal scaffolding. This alteration makes the growth cone collapse, steering the axon in a new direction or halting its growth. In chicken motor neurons whose ephexin1 was inactivated, the axons grew into the hind limb prematurely, indicating faulty axon guidance.

"Understanding these pathways could help in understanding the process of nerve regeneration," says Greenberg, who is also Professor of Neurology and Neurobiology at Harvard Medical School. "The mechanisms we've uncovered could provide opportunities for the development of therapies for spinal cord injury, targeting ephexin and possibly Vav," he speculates, "but much more needs to be known about how ephexin, Vav and other proteins work together to coordinate axon guidance."


'"/>

Source:Children's Hospital Boston


Related biology news :

1. Wisconsin scientists grow critical nerve cells
2. Clam embryo study shows pollutant mixture adversely affects nerve cell development
3. Zebrafish may hold key to understanding human nerve cell development
4. New component of the brakes on nerve regeneration found
5. Molecular messengers perform a crucial role in the ability of injured nerve cells to heal themselves
6. Diabetic nerve therapy shows striking results
7. Malfunctioning bone marrow cells sabotage nerve cells in diabetes
8. UIC researchers show protein routes messages in nerve cells
9. Researchers find molecule that inhibits regrowth of spinal nerve cells
10. Gradient guides nerve growth down spinal cord
11. Scientists discover the molecular switch for nerve cells insulating jelly rolls
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:1/26/2017)... DENVER , Jan. 26, 2017  Acuity ... Trends for Biometrics and Digital Identity".  Acuity characterizes ... digital identity when increased adoption reflects a new ... "Biometrics and digital identity are ... says Maxine Most , Principal of Acuity ...
(Date:1/24/2017)... , Jan. 24, 2017  It sounds ... baby,s sock that monitors vital signs and alerts ... an infant,s oxygen saturation level drops. But pediatric ... alarm to parents, with no evidence of medical ... devices are marketed aggressively to parents of healthy ...
(Date:1/19/2017)... PUNE, India , January 19, 2017 ... Sensor Market, Opportunities and Forecast, 2014 - 2022," the global biometric sensor ... of 9.6% from 2016 to 2022. In 2015, Asia-Pacific ... for both public and private sectors. Continue Reading ... ...
Breaking Biology News(10 mins):
(Date:2/24/2017)... Provectus Biopharmaceuticals, Inc. (OTCQB: PVCT, ... oncology and dermatology biopharmaceutical company, today is providing ... its previously announced rights offering of up to ... stock and Series C Convertible Preferred Stock to ... As previously announced, the rights offering ...
(Date:2/24/2017)... N.J. , Feb. 24, 2017  Driven ... and biotechnology are now the fastest growing categories, ... Specialty Actives in Personal Care: Multi-regional Market ... research and management consulting firm Kline. ... bioprocesses that make them more effective for skin ...
(Date:2/24/2017)... Inc. (NASDAQ: CBPO) ("China Biologic" or the "Company"), a leading ... financial results for the fourth quarter and fiscal year of ... Total sales in the fourth quarter of ... 13.6% in USD terms to $77.6 million from $68.3 million ... profit increased by 13.3% to $46.8 million from $41.3 million ...
(Date:2/23/2017)... NEW YORK , Feb. 23, 2017 ... a leading digital health company, and Digital ... telemedicine and remote patient monitoring, announce they are ... DN Telehealth maximizes collaboration compatibility ... extending consultations beyond a physical clinical setting to ...
Breaking Biology Technology: