much like the electrical wiring in homes, nerves in the body need to be completely covered by a layer of insulation to work properly. The wiring in the nervous system is protected by layers of an insulating protein called myelin. These layers increase the speed of nerve impulses that travel throughout the brain and the body.
The formation of myelin sheaths during development requires a complex choreography of the interaction between different kinds of cells. A group of Vanderbilt University at Tennessee researchers has successfully produced movies that provide the first direct view of the initial stage of this process the period when the cells that ultimately produce the myelin sheathing spread throughout the developing nervous system. The results were published online in the journal Nature Neuroscience on November 12 and should aid in the design of new therapies to promote the repair of myelin after disease or injury.
"We discovered that this process is far more dynamic than anyone had dreamed," says Bruce Appel, associate professor of biological sciences and Kennedy Center investigator who headed the study. In the central nervous system, the myelin membranes are produced by cells called oligodendrocytes. These cells must be distributed uniformly along axons--the long, wire-like extensions from neurons that carry nerve impulses--so that the membranes, which wrap the nerve fibres like millions of microscopic pieces of electrician's tape, can cover the axons completely and uniformly. The wrapping process takes place near the end of foetal development and continues for some time after birth.
In order to study this process, Appel and his research group created a transgenic zebrafish which incorporate fluorescent proteins in the cells involved in myelination. The zebrafish is a small tropical fish that has become a popular species for studying the process of development in vertebrates (animals with backbones). Because zebrafish embryos are transparent and develop within a few days, they allow biologists to watch developmental processes as they take place something they cannot do with mice or other mammals. These characteristics allowed the Vanderbilt researchers to obtain images of the cells involved in myelination using a confocal microscope and edit them into time-lapse movies.
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