There are three kinds of glial cells in the brain, oligodendrocyte, astrocyte and microglia. Oligodendrocytes myelinate neuronal axons to increase conduction velocity of neuronal impulses. A Japanese research team in National Institute for Physiological Sciences (NIPS, Okazaki, Aichi, Japan) finds a characteristic feature of oligodendrocytes that selectively myelinate a particular set of neuronal axons.
It is known that maturation of oligodendrocyte is necessary for motor skill learning. The structure of the white matter changes after motor skill learning (e.g., juggling or playing piano). These reports suggest that a single oligodendrocytes selectively myelinate a particular set of axons. In addition, oligodendrocyte dysfunction causes severe neurological disorders, such as multiple sclerosis. So, better understanding of interaction between oligodendrocytes and neuronal axons is highly desired. However, it was difficult to identify interaction between oligodendrocyte and neuronal axons in the brain because the high density of oligodendrocytes in the white matter prevents us from detecting precise morphology of each oligodendrocyte.
The Japanese research group in NIPS found one of the viral vectors labels single oligodendrocytes in the white matter. Using multiple viral vector injections, neuronal axons derived from distinct brain region (motor cortex or sensory cortex) and oligodendrocytes in the white matter were simultaneously labeled. Surprisingly, the research group found that oligodendrocyte did not just ensheath axons randomly, but some oligodendrocytes selectively myelinated axons from a particular brain region.
This method developed by the research group can be available for demyelinating animal model to assess demyelinating diseases. “Now, we plan to analyze oligodendrocyte morphology and myelination in demyelinating mouse models” corresponding author Dr. Shimizu says. “Furthermore, axon selective myelination for a specific neuronal subtype found in this study encourages us to investigate physiological relevance of multiple myelination to higher brain function.”