Motor nerve targeting to limb muscles is controlled by ephrin proteins

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Motor nerve targeting to limb muscles is controlled by ephrin proteins

http://www.eurekalert.org/pub_releases/2008-12/idrc-mnt122208.php

A study from a team of researchers including Dr. Artur Kania,

Director of the Neural Circuit Development Research Unit at the IRCM,

and Dr. Dayana Krawchuk, postdoctoral fellow, shows how a family of

proteins present in the developing limb control nerve targeting from

the spinal cord to the muscles of the limb. This discovery, co-

authored by scientists from Columbia University in New York City, is

published on December 26, 2008 in the journal Neuron.

The nervous system is a highly precise and intricate nerve network

whose major purpose is to analyze and respond to external stimuli

through coordinated movement. Such precision stems from the accuracy

of nerve connections formed between neurons and muscles. " To

understand how this occurs, " explains Dr. Kania, " we study a simple

system in which nerves extend from the spinal cord to the limb to

connect to either flexor muscles (i.e. biceps arm muscle) or extensor

muscles (i.e. triceps arm muscle). " Previously, the researchers found

that nerves connecting to extensor muscles were guided towards

specific targets by a protein present in the developing limb (ephrin-

A). Using chick and mouse embryos as models, the team of scientists

now discovered that nerves connecting to the antagonist muscle group,

the flexor muscles, are guided by a closely-related protein family,

also present in the developing limb (ephrin-. Together, these

studies present a complete picture of how both limb nerves correctly

connect the nervous system to muscles. Furthermore, by studying the

wiring of a relatively simple nerve connection, the team of

scientists has discovered a molecular strategy that is very likely

widely used in the nervous system to wire much more complex neural

circuits, such as those required for learning, memory and coordinated

movement.

Miswiring of the nervous system is thought to be a factor in

disorders such as epilepsy and mental retardation. By studying the

process of limb nerve development, this team of scientists

contributes further to the development of new strategies for

treatment of patients with a diseased and damaged nervous system.

That is because knowing how nerves form is crucial in designing

therapies that aim to rebuild damaged or diseased nerves.

" The study of the ephrin proteins should help us understand diseases

such as autism, schizophrenia as well as a number of neurological

disorders, " says Dr. Rémi Quirion, a scientific director at the

Canadian Institutes of Health Research (CIHR). " We are proud to

support this important study and hope it will help to improve the

lives of people with these health problems. "