Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Gradient guides nerve growth down spinal cord


The same family of chemical signals that attracts developing sensory nerves up the spinal cord toward the brain serves to repel motor nerves, sending them in the opposite direction, down the cord and away from the brain, report researchers at the University of Chicago in the September 2005 issue of Nature Neuroscience (available online August 14). The finding may help physicians restore function to people with paralyzing spinal cord injuries.

Growing nerve cells send out axons, long narrow processes that search out and connect with other nerve cells. Axons are tipped with growth cones, bearing specific receptors, which detect chemical signals and then grow toward or away from the source.

In 2003, University of Chicago researchers reported that a gradient of biochemical signals known as the Wnt proteins acted as a guide for sensory nerves. These nerves have a receptor on the tips of their growth cones, known as Frizzled3, which responds to Wnts.

In this paper, the researchers show that the nerves growing in the opposite direction are driven down the cord, away from the brain, under the guidance of a receptor, known as Ryk, with very different tastes. Ryk sees Wnts as repulsive signals.

"This is remarkable example of the efficiency of nature," said Yimin Zou, Ph.D., assistant professor of neurobiology, pharmacology and physiology at the University of Chicago. "The nervous system is using a similar set of chemical signals to regulate axon traffic in both directions along the length of the spinal cord."

It may also prove a boon to clinicians, offering clues about how to grow new connections among neurons to repair or replace damaged nerves. Unlike many other body components, damaged axons in the adult spinal cord cannot adequately repair themselves. An estimated 250,000 people in the United States suffer from permanent spinal cord injuries, with about 11,000 new cases each year.

This study focused on corticospinal neurons, which control voluntary movements and fine-motor skills. These are some of the longest cells in the body. The corticospinal neurons connect to groups of neurons along the length of spinal cord, some of which reach out of the spinal cord. They pass out of the cord between each pair of vertebrae and extend to different parts of the body, for example the hand or foot.

Zou and colleagues studied the guidance system used to assemble this complex network in newborn mice, where corticospinal axon growth is still underway. Before birth, axons grow out from the cell body of a nerve cell in the motor cortex. The axons follow a path back through the brain to the spinal cord.

By the time of birth, the axons are just growing into the cord. During the first week after birth they grow down the cervical and thoracic spinal cord until they reach their proper position, usually after seven to ten days.

From previous studies, Zou and colleagues knew that a gradient of various Wnt proteins, including Wnt4, formed along the spinal cord around the time of birth. Here they show that two other proteins, Wnt1 and Wnt5a are produced at high concentrations at the top of the cord and at consecutively lower levels farther down.

They also found that motor nerves are guided by Wnts through a different receptor, called Ryk, that mediates repulsion by Wnts. Antibodies that blocked the Wnt-Ryk interaction blocked the downward growth of corticospinal axons when injected into the space between the dura and spinal cord in newborn mice.

This knowledge, coupled with emerging stem cell technologies, may provide the most promising current approach to nervous system regeneration. If Wnt proteins could be used to guide transplanted nerve cells -- or someday, embryonic stem cells -- to restore the connections between the body and the brain, "it could revolutionize treatment of patients with paralyzing injuries to these nerves," Zou suggests.

"Although half the battle is acquiring the right cells to repair the nervous system," he said, "the other half is guiding them to their targets where they can make the right connections."

"Understanding how the brain and the spinal cord are connected during embryonic development could give us clues about how to repair damaged connections in adults with traumatic injury or degenerative disorders," Zou added.

The National Institute of Neurological Disorders and Stroke, the Schweppe Foundation, the Robert Packard ALS Center at Johns Hopkins, the University of Chicago Brain Research Foundation and the Jack Miller Peripheral Neuropathy Center supported this study.

Additional authors include Yaobu Liu, Jun Shi. Chin-Chun Lu, and Anna Lyuksyutova of the University of Chicago, and Zheng-Bei Wang and Xuejun Song of the Parker College Research Institute in Dallas Texas.

John Easton | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München

nachricht Second research flight into zero gravity
21.10.2016 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>