Oligodendrocyte

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**Oligodendrocyte**
General Information

Tissue type	Nervous
Cell type	Neuroglia
Location	Central nervous system
Role	Myelination
Identification	Robertson, 1899
Ultrastructure
Soma size	10–20μm
Unique organelles	None
Unique feature	Myelinating processes

Oligodendrocytes (from Greek literally meaning few tree cells), or oligodendroglia (Greek, few tree glue),^[1] are a variety of neuroglia. Their main function is the myelination of axons exclusively in the central nervous system of the higher vertebrates, a function performed by Schwann cells in the peripheral nervous system. A single oligodendrocyte can extend to up to 50 axons, wrapping around approximately 1 mm of each and forming the myelin sheath.

1 Origin
2 Function
3 Pathology
4 Notes
5 References

[edit] Origin

Oligodendroglia arise during development from an oligodendrocyte precursor cell which can be identified by its expression of a number of antigens, including the ganglioside GD3 (Curtis et al., 1988; LeVine and Goldman, 1988; Hardy and Reynolds, 1991; Levine et al., 1993), the NG2 chondroitin sulfate proteoglycan (Levine et al., 1993), and the platelet derived growth factor-alpha receptor subunit (PDGF-alphaR) (Pringle et al., 1992). In the rat forebrain the majority of oligodendroglial progenitors arise during late embryogenesis and early postnatal development from cells of the subventricular zones (SVZ) of the lateral ventricles. SVZ cells migrate away from these germinal zones to populate both developing white and gray matter, where they differentiate and mature into myelin-forming oligodendroglia (Hardy and Reynolds, 1991; Levison and Goldman, 1993). However, it is not clear whether all oligodendroglial progenitors undergo this sequence of events. It has been suggested that some undergo apoptosis (Barres et al., 1992) and that some fail to differentiate into oligodendroglia but persist into maturity as adult oligodendroglial progenitors (Wren et al., 1992).

[edit] Function

The nervous system of mammals depends crucially on this sheath for insulation as it results in decreased ion leakage and lower capacitance of the cell membrane. There is also an overall increase in impulse speed as saltatory propagation of action potentials occurs at the nodes of Ranvier in between Schwann cells (of the PNS) and oligodendrocytes (of the CNS); furthermore miniaturization occurs, whereby impulse speed of myelinated axons increases linearly with the axon diameter, whereas the impulse speed of unmyelinated cells increases only with the square root of the diameter.

As part of the nervous system they are closely related to nerve cells and like all other glial cells the oligodendrocytes have a supporting role towards neurons. They are intimately involved in signal propagation, providing the same functionality as the insulation on a household electrical wire.

[edit] Pathology

Diseases that result in injury to the oligodendroglial cells include demyelinating diseases such as multiple sclerosis and leukodystrophies. Oligodendroglia are also susceptible to infection by the JC virus, which causes progressive multifocal leukoencephalopathy (PML), a condition which specifically affects white matter, typically in immunocompromised patients. Tumors of oligodendroglia are called oligodendrogliomas.

[edit] Notes

^ (Ragheb 1999, p. 14).

[edit] References

Ragheb, Fadi (1999), The M3 Muscarinic Acetylcholine Receptor Mediates p42^mapk Activation and c-fos mRNA Expression in Oligodendrocyte Progenitors, Ottawa: National Library of Canada [2006-03-07]

Raine, C.S. (1991). Oligodendrocytes and central nervous system myelin. In Textbook of Neuropathology, second edition, R.L. Davis and D.M. Robertson, eds. (Baltimore, Maryland: Williams and Wilkins), pp. 115–141.