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Description
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Glial Fibrillary Acid Protein (GFAP) was discovered by Bignami et al. (Ref. 1) as a majorfibrous protein of multiple sclerosis plaques. It was subsequently found to be a member ofthe 10 nm or intermediate filament protein family, specifically the intermediate filamentprotein family Class III, which also includes peripherin, desmin and vimentin. GFAP isheavily, and specifically, expressed in astrocytes and certain other astroglia in the centralnervous system, in satellite cells in peripheral ganglia, and in non-myelinating Schwanncells in peripheralnerves. (Ref. 2) Many types of brain tumors, presumably of astrocytic origin, heavily expressGFAP. In addition, neural stem cells frequently strongly express GFAP. It is also found in thelens epithelium, Kupffer cells of the liver, in some cells of salivary tumors, and has beenreported in erythrocytes. Therefore, antibodies to GFAP are very useful as markers ofastrocytic cells and neural stem cells, and for distinguishing neoplasms of astrocytic originfrom other neoplasms in the central nervous system. Although its function is not fully understood, GFAP protein is probably involved incontrolling the shape and movement of astrocytes. The protein may also play a significantrole in the interactions of astrocytes with other cells, which are required for the formationand maintenance of the myelin layer that covers nerve cells. Additionally, GFAP may assist in maintaining the protective blood-brain barrier. In adults, GFAP levels increase as a result of the proliferation of astrocytes that occurs inresponse to a variety of physical, chemical and etiological insults, including Alzheimer'sdisease, epilepsy and multiple sclerosis. Alexander's disease was recently shown to be caused by point mutations in theprotein-coding region of the GFAP gene. (Ref. 3) All forms of Alexander's disease arecharacterized by the presence of Rosenthal fibers, which are GFAP-containing cytoplasmicinclusions found in astrocytes.
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