Originally published November 8 2005
Research on motor neurons reveals code for motor function in muscles
by Mike Adams, the Health Ranger, NaturalNews Editor
A team of scientists at Howard Hughes Medical Institute have discovered part of the code that governs the relationship between motor neurons and specific muscles in the body.
The studies suggest that the code --- which involves members of the family of transcription factors encoded by the Hox genes --- could also govern the establishment of other spinal cord circuits.
This circuitry includes interneurons that control motor neuron firing patterns and sensory neurons that transmit feedback information on muscle action.
The research team, which was led by HHMI investigator Thomas M. Jessell, published its findings in the November 4, 2005, issue of the journal Cell.
Earlier work performed by Dasen and Jessell, in collaboration with Jeh-Ping Liu, who is now at the University of Virginia, established that certain Hox proteins control the differentiation of motor neurons into columns in the spinal cord.
Using these antibodies, Dasen and colleagues pinpointed the pattern of expression of each protein within the set of motor neurons that project to limb muscles.
"Once we had these reagents, we were able to obtain the high resolution maps of Hox expression that were necessary to address more complex aspects of Hox function in motor neuron diversification," said Jessell.
To give an idea of the extent of complexity, Jessell explained, "there are few motor columns, yet within each of the columns that projects to the limb there are at least fifty different subtypes of motor neurons, termed motor pools.
Jessell said this code appears to govern three levels of motor neuron organization: the columnar organization that ensures that motor neurons project into the limb; the divisional organization of motor neurons that determines whether motor neurons project to muscles in the dorsal or ventral halves of the limb; and finally, the motor neuron pool identity that governs the muscle target of each set of motor neurons.
"Or, it could be that injury causes subtle alterations in the wiring of spinal circuits, and these alterations may constrain the capacity for full recovery of motor function.
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