Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Salk scientists identify key nerve navigation pathway

23.11.2007
A mutation named Magellan steers nerve cells off course

Newly launched nerve cells in a growing embryo must chart their course to distant destinations, and many of the means they use to navigate have yet to surface. In a study published in the current issue of the journal Neuron, scientists at the Salk Institute for Biological Studies have recovered a key signal that guides motor neurons – the nascent cells that extend from the spinal cord and must find their way down the length of limbs such as arms, wings and legs.

The Salk study, led by Samuel Pfaff, Ph.D, a professor in the Gene Expression Laboratory, identifies a mutation they christened Magellan, after the Portuguese mariner whose ship Victoria was first to circumnavigate the globe. The Magellan mutation occurs in a gene that normally pilots motor neurons on the correct course employing a newly discovered mechanism, their results demonstrate.

In the mutants, growing neurons can be seen leaving the spinal cord normally but then appear to lose direction. The elongating cells develop “kinks” and sometimes fold back on themselves or become entwined in a spiral, forming coils outside the spinal cord. “They appear to become lost in a traffic roundabout,” described Pfaff, who observed the growing neurons with fluorescent technology.

... more about:
»Axon »Magellan »Mutation »Nerve »Neuron »cone »receptor

Understanding how motor neurons reach the appropriate targets is necessary for the implementation of novel therapies, including embryonic stem cell replacement for the treatment of presently incurable disorders such as Lou Gehrig’s disease, in which motor neurons undergo irreversible decay.

“Embryonic studies provide useful insights on how to replicate the system in an adult,” said Pfaff. And, as he also pointed out, the mechanisms used by motor neurons are likely to be similar to those used in other parts of the central nervous system, such as the brain. The Magellan mutation discovered by Pfaff’s group was found in mice, but the affected gene, called Phr1, has also been identified in other model systems, including fruit flies and the worm species C. elegans.

A growing nerve bears at its bow a structure called the growth cone, a region rich in the receptor molecules whose job is to receive cues from the environment, much as ancient mariners who observed the stars and set their course accordingly. During development, the growth cone continuously pushes forward, while the lengthening neuron behind it matures into the part of the cell called the axon. Once the growing cell “lands” at its target in a muscle cell, it is the axon that will relay the messages that allow an animal to control and move its limbs at will.

In Magellan mutants, Pfaff’s team discovered that the growth cone becomes disordered. Rather than forming a distinct “cap” on the developing neuron, the cone is dispersed in pieces along both the forward end and the axon extending behind it.

“The defect is found in the structure of the neuron itself,” said Pfaff, noting that the fundamental pieces, such as the receptors capable of reading cues, all seem to be present. Without the correct orientation of receptors, however, signals cannot be read accurately, resulting in growth going off course.

“A precise gradient normally exists across the cone,” said Pfaff, “which is disrupted in the Magellan mutants.” As a result, cells lose their polarity. They literally do not know the front end from the back end, according to Pfaff. This sense of polarity is a universal feature common to all growing neurons. Therefore, “Phr1 is likely to play a role in most growing neurons to ensure their structure is retained at the same time they are growing larger,” he said.

Pfaff and his group identified Magellan using a novel system they had developed, in which individual motor neurons and axons can be visualized fluorescently. They were able to screen more than a quarter of a million mutations, and the mutations of interest were rapidly mapped to known genes as a result of the availability of the sequenced mouse genome – a byproduct of the effort to sequence entire genomes such as that in the human.

The Magellan mutation is located in a gene known as Phr1, which is also active in other parts of the nervous system, indicating that it most likely functions to steer other types of neurons, such as those that enervate sensory organs or connect different regions of the brain. Studies of Magellan may therefore shed light on how a variety of neurological disorders might be treated with cell replacement strategies.

Gina Kirchweger | EurekAlert!
Further information:
http://www.salk.edu

Further reports about: Axon Magellan Mutation Nerve Neuron cone receptor

More articles from Life Sciences:

nachricht Bare bones: Making bones transparent
27.04.2017 | California Institute of Technology

nachricht Link Discovered between Immune System, Brain Structure and Memory
26.04.2017 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>