Abstract
In the spinal cord, the axonal tracts with various caliber sizes are myelinated by oligodendrocytes and function as high-velocity ways for motor and sensory nerve signals. In some neurological disorders, such as multiple sclerosis, demyelination of small caliber axons is observed in the spinal cord. While type I/II oligodendrocytes among the four types are known to myelinate small diameter axons, their characteristics including identification of regulating molecules have not been understood yet. Here, we first found that in the wild-type mouse spinal cord, type I/II oligodendrocytes, positive for carbonic anhydrase II (CAII), were located in the corticospinal tract, fasciculus gracilis, and the inside part of ventral funiculus, in which small diameter axons existed. The type I/II oligodendrocytes started to appear between postnatal day (P) 7 and 11. We further analyzed the type I/II oligodendrocytes in the mutant mice, whose small diameter axons were hypomyelinated due to the deficiency of teneurin-4. In the teneurin-4 deficient mice, type I/II oligodendrocytes were significantly reduced, and the onset of the defect was at P11. Our results suggest that CAII-positive type I/II oligodendrocytes myelinate small caliber axons in the spinal cord and teneurin-4 is the responsible molecule for the generation of type I/II oligodendrocytes.
Highlights
The spinal cord takes on the core roles in our neuronal activity of the central nervous system (CNS)
We found that there were many carbonic anhydrase II (CAII)-positive type I/II oligodendrocytes around the small caliber axons, especially in the VFi, corticospinal tract (CST), and fasciculus gracilis (FG) of the white matter (WM) of the spinal cord
Our results in this report showed that first, CAII-positive type I/II oligodendrocytes were preferentially located in the small caliber axon areas and initiated to appear from P7 to P11 in the WT spinal cord
Summary
The spinal cord takes on the core roles in our neuronal activity of the central nervous system (CNS). After www.nature.com/scientificreports the discovery by del Río Hortega, Butt and his colleagues identified carbonic anhydrase II (CAII) as a marker for type I/II oligodendrocytes[16,17,19] They demonstrated that CAII-positive cells in the anterior medullary velum (AMV) extended their complexly arborized processes to the small diameter axons. From our results using 7-week-old WT spinal cord, CAII-positive cells were found in the whole spinal cord, but were accumulated in the CST, FG, and the inside part of VF, in which small diameter axons existed. These cells emerged from postnatal day (P) 7 to 11. This is the first report that identified a regulator of specific types (type I/II) of oligodendrocytes
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