The evolutionary prerequisites of myelin -- the fatty substance that insulates axons and enables rapid communication between cells of the nervous system in jawed vertebrates -- are described in new research in fish published in JNeurosci .
Myelinated axons increases a neuron's transmission speed by as much as 100 times that of an unmyelinated axon. Myelin is not present in jawless vertebrates, which diverged from the jawed vertebrates approximately 560 million years ago.
Taking advantage of recent technical advances in visualization techniques, Wiebke Möbius, Hauke Werner, and colleagues observed the spinal cord and part of the peripheral nervous system in the sea lamprey. Axons of the lamprey lateral line nerve were all surrounded by glial cells, which are responsible for myelination in the jawed vertebrates. These glial cells expressed the equivalent genes expressed by the Schwann cells that myelinate axons of the peripheral nervous system in mammals. Similarly in the spinal cord, the researchers observed glial cells resembling astrocytes. The larger size of axons in adult lamprey compared to the larval stage may enable rapid signal transmission, suggesting that myelin may have evolved to achieve similarly fast neuronal communication in the much smaller axons of jawed vertebrates.
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Article: Axonal ensheathment in the nervous system of lamprey: Implications for the evolution of myelinating glia
DOI: https://doi.org/10.1523/JNEUROSCI.1034-18.2018
Corresponding authors: Wiebke Möbius, Moebius@em.mpg.de and Hauke Werner, Hauke@em.mpg.de (Max Planck Institute of
Experimental Medicine, Göttingen, Germany)
About JNeurosci
JNeurosci , the Society for Neuroscience's first journal, was launched in 1981 as a means to communicate the findings of the highest quality neuroscience research to the growing field. Today, the journal remains committed to publishing cutting-edge neuroscience that will have an immediate and lasting scientific impact, while responding to authors' changing publishing needs, representing breadth of the field and diversity in authorship.
About The Society for Neuroscience
The Society for Neuroscience is the world's largest organization of scientists and physicians devoted to understanding the brain and nervous system. The nonprofit organization, founded in 1969, now has nearly 37,000 members in more than 90 countries and over 130 chapters worldwide.