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Oligodendrocytes (from Greek, meaning ''cells with a few branches''), or oligodendroglia (Greek, ''few tree glue''),〔.〕 are a type of neuroglia. Their main functions are to provide support and insulation to axons in the central nervous system of some vertebrates, equivalent to the function performed by Schwann cells in the peripheral nervous system. Oligodendrocytes do this by creating the myelin sheath, which is 80% lipid and 20% protein.〔Carlson, Physiology of Behavior, 2010〕 A single oligodendrocyte can extend its processes to 50 axons, wrapping approximately 1 μm of myelin sheath around each axon; Schwann cells, on the other hand, can wrap around only one axon. Each oligodendrocyte forms one segment of myelin for several adjacent axons.〔 ==Origin== Oligodendroglia, types of glial cells, arise during development from oligodendrocyte precursor cells, which can be identified by their expression of a number of antigens, including the ganglioside GD3,〔Curtis et al., 1988; LeVine and Goldman, 1988; Hardy and Reynolds, 1991〕 the NG2 chondroitin sulfate proteoglycan, and the platelet-derived growth factor-alpha receptor subunit (PDGF-alphaR). Most oligodendrocytes develop during embryogenesis and early postnatal life from restricted periventricular germinal regions.〔Vallstedt et al., 2004〕 Oligodendrocytes are found only in the central nervous system which comprises the brain and spinal cord. These cells were originally thought to have been produced in the ventral neural tube; however, research now shows oligodendrocytes originate from the ventral ventricular zone of the embryonic spinal cord and possibly have some concentrations in the forebrain. They are the last cell type to be generated in the CNS. Myelination is only prevalent in a few brain regions at birth and continues into adulthood. The entire process is not complete until about 25–30 years of age.〔Fields, 2008〕 The group of Prof. Arturo Alvarez-Buylla demonstrate that oligodendrocyte formation in the adult brain is associated with glial-restricted progenitor cells, known as oligodendrocyte progenitor cells (OPCs). SVZ cells migrate away from 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 others fail to differentiate into mature oligodendroglia but persist as adult oligodendroglial progenitors.〔Wren et al., 1992〕 Remarkably, oligodendrocyte population originated in the subventricular zona can be dramatically expanded by administering epidermal growth factor (EGF). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Oligodendrocyte」の詳細全文を読む スポンサード リンク
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