Mutations in a protein called dynein cause defects in mice that are similar to those seen in humans with peripheral neuropathy, according to researchers at the University of Chicago Medical Center.
The Univ. of Chicago team reports that mice with mutations in only one copy of a gene coding for one part of dynein have severe defects in proprioception, the ability to perceive the spatial orientation of body parts.
“This gene codes for part of a multiprotein complex,” explains study author Brian Popko, Ph.D., Jack Miller professor in neurological diseases at the University of Chicago Medical Center. “So a mutation in any of these proteins, or disruption in the function of this multiprotein complex through some other mechanism, could also lead to very similar abnormalities” in human patients with sensory neuropathies.
Dynein is required for the proper functioning of sensory nerve cells. The genetic defects identified in the study caused a significant reduction in the number of sensory nerve cells in the affected mice, the scientists report.
Also, mutations in the gene for dynein heavy chain 1, Dync1h, led to movement defects in the hind legs of mice. These defects resembled human neuropathies, according to Dr. Popko, particularly some forms of Charcot-Marie-Tooth disease and hereditary sensory neuropathy.
Although dynein is important for the whole body, defects are found only in sensory neurons and predominantly in hind limbs, the investigators note. “The key question is why,” points out Dr. Popko. “This mutation may affect transport proteins in all neurons, but perhaps the region that is mutated is more important for the proteins that it transports in sensory neurons, whereas other regions could play a role in motor neurons. Also, mutations in different regions of this protein seem to have different effects. That may be due to differences in the cargo-binding domains.”
Dr. Popko and his group say that they are already looking at human patients for similar mutations. They are also trying to answer new questions such as what are the binding partners of dynein that are disrupted in diseases and why does this affect sensory and not motor neurons.
The current study is reported in the December 26 issue of The Journal of Neuroscience.