From the WUSTL Newsroom…
Scientists have identified a gene that helps regulate how well nerves of the central nervous system are insulated, researchers at Washington University School of Medicine in St. Louis report.
Healthy insulation is vital for the speedy propagation of nerve cell signals. The finding, in zebrafish and mice, may have implications for human diseases like multiple sclerosis, in which this insulation is lost.
The study appears Jan. 21 in Nature Communications.
Nerve cells send electrical signals along lengthy projections called axons. These signals travel much faster when the axon is wrapped in myelin, an insulating layer of fats and proteins. In the central nervous system, the cells responsible for insulating axons are called oligodendrocytes.
The research focused on a gene called Gpr56, which manufactures a protein of the same name. Previous work indicated that this gene likely was involved in central nervous system development, but its specific roles were unclear.
In the new study, the researchers found that when the protein Gpr56 is disabled, there are too few oligodendrocytes to provide insulation for all of the axons. Still, the axons looked normal. And in the relatively few axons that were insulated, the myelin also looked normal. But the researchers observed many axons that were simply bare, not wrapped in any myelin at all.
Without Gpr56, the cells responsible for applying the insulation failed to reproduce themselves sufficiently, according to the study’s senior author, Kelly R. Monk, PhD, assistant professor of developmental biology. These cells actually matured too early instead of continuing to replicate as they should have. Consequently, in adulthood, there were not enough mature cells, leaving many axons without insulation.
Monk and her team study zebrafish because they are excellent models of the vertebrate nervous system. Their embryos are transparent and mature outside the body, making them useful for observing developmental processes.
“We first saw this defect in the developing zebrafish embryo,” said first author Sarah D. Ackerman, a graduate student in Monk’s lab. “But it’s not simply a temporary defect that only results in delayed myelination. When I looked at fish that were six months old, I still saw this problem of undermyelinated axons.”
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