Evidence for myelin sheath remodeling revealed by in vivo imaging

February 15, 2018, Technical University Munich
Using newly developed markers, the scientists were able to visualize axons, myelin, and nodes of Ranvier in vivo. A version of this image is used in the current article in Current Biology, DOI: 10.1016/j.cub.2018.01.017 (CC BY-NC-ND 4.0) ) Credit: Czopka / TUM

Nerve fibers are surrounded by a myelin sheath. Scientists at the Technical University of Munich (TUM) have now made the first-ever "live" observations of how this protective layer is formed. The team discovered that the characteristic patterns of the myelin layer are determined at an early stage. However, these patterns can be adjusted as needed in a process apparently controlled by the nerve cells themselves.

The myelin sheath surrounding the axons are comparable to the insulation covering an electric wire. Without it, the rapid propagation of electric signals would not be possible. Damage to this insulating layer, for example from illnesses such as , may result in serious impairments.

But myelin does not form a continuous coating along the axon. Instead, it is divided into segments. These can vary in length and are separated by gaps known as nodes of Ranvier. For the complex network of the central nervous system to function properly, the speed of the connections is not the only consideration. The crucial factor is the fine tuning: the signals have to reach the right place at exactly the right time. The transmission speed of information through an axon is partly determined by the number and length of the segments.

The bodies of humans and animals have some ability to repair damaged myelin sheaths. Dr. Tim Czopka, a neuroscientist at TUM, has succeeded in making the first-ever in vivo observations of this process. Czopka and his team used newly developed markers to visualize the formation myelin segments surrounding axons in the spinal cords of zebrafish. They conclude that characteristic patterns made up of myelin segments with different lengths along an axon are defined within a few days after myelin formation begins. Although the segments continue growing from that time onward as the body of the zebrafish grows, the pattern is preserved.

Time lapse video of a zebrafish showing rapid growth of two nascent myelin sheaths. This video is part of the supplementary material to Auer et al., „Evidence for Myelin Sheath Remodeling in the CNS Revealed by In Vivo Imaging", Current Biology (2018). 10.1016/j.cub.2018.01.017 Credit: Czopka /TUMLicensed under (CC BY-NC-ND 4.0)

Following this observation, the researchers destroyed selected segments. "What happened next surprised us," says Tim Czopka. "After the destruction of the segments, the began to dynamically remodel. In the end, the damage was repaired and in most cases the original pattern was restored." The regeneration followed a fixed sequence. First, the adjacent segments expanded to close the gap. A new segment then formed between them, and they contracted to their original size.

This raises an important question: Who controls the emergence and the restoration of the segment pattern? "Our observations suggest that it is not the oligodendrocytes—the cells that form myelin—that decide where it is formed, but rather the axons," says Tim Czopka. "You could say that they know best which is needed for the signals to be transmitted at optimal speed."

The team is now studying how the segment patterns are affected by the targeted stimulation of nerve cell activity and by the neurotransmitters released as a result. "If we can understand the role of the axons in generation and remodelling, it may yield new approaches to controlling it," explains Czopka. "That would be relevant for the treatment of illnesses such as multiple sclerosis."

Explore further: Multiple sclerosis—cholesterol crystals prevent regeneration in central nervous system

More information: F. Auer, S. Vagionitis, T. Czopka, "Evidence for Myelin Sheath Remodeling in the CNS Revealed by In Vivo Imaging", Current Biology (2018). DOI: 10.1016/j.cub.2018.01.01

Related Stories

Multiple sclerosis—cholesterol crystals prevent regeneration in central nervous system

January 5, 2018
Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system, in which the body's own immune cells attack the fatty, insulating myelin sheath surrounding nerve fibers. The regeneration of intact ...

A little myelin goes a long way to restore nervous system function

October 24, 2017
In the central nervous system of humans and all other mammals, a vital insulating sheath composed of lipids and proteins around nerve fibers helps speed the electrical signals or nerve impulses that direct our bodies to walk, ...

Use it or lose it

August 2, 2017
An Ludwig Maximilian University of Munich study reveals that sound-evoked activity of neurons in the auditory system of the mouse increases the thickness of their myelin sheaths - and enhances the speed of signal transmission ...

Glial cells assist in the repair of injured nerves

January 28, 2013
When a nerve is damaged, glial cells produce the protein neuregulin1 and thereby promote the regeneration of nerve tissue.

Recommended for you

Being hungry shuts off perception of chronic pain

March 22, 2018
Pain can be valuable. Without it, we might let our hand linger on a hot stove, for example. But longer-lasting pain, such as the inflammatory pain that can arise after injury, can be debilitating and costly, preventing us ...

From signal propagation to consciousness: New findings point to a potential connection

March 22, 2018
Researchers at New York University have discovered a novel mechanism through which information can be effectively transmitted across many areas in the brain—a finding that offers a potentially new way of understanding how ...

Using simplicity for complexity—new research sheds light on the perception of motion

March 22, 2018
A team of biologists has deciphered how neurons used in the perception of motion form in the brain of a fly —a finding that illustrates how complex neuronal circuits are constructed from simple developmental rules.

Stiffness of connection influences exchange of physical cues during coordinated movements

March 22, 2018
When two people coordinate their movements, such as by holding hands or moving furniture, they exchange physical cues through the objects that connect them. New research published in PLOS Computational Biology suggests that ...

Focus on early stage of illness may be key to treating ALS, study suggests

March 22, 2018
A new kind of genetically engineered mouse and an innovation in how to monitor those mice during research have shed new light on the early development of an inherited form of amyotrophic lateral sclerosis (ALS).

Flow of spinal fluid disrupted in inherited developmental disorder

March 22, 2018
Scientists have pinpointed the mechanism behind hydrocephalus, an accumulation of cerebrospinal fluid around the brain, in an inherited developmental disorder called Noonan syndrome.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.