Glial fibrillary acidic protein (GFAP), a class-III intermediate filament, is a cell-specific marker that, during the development of the central nervous system, distinguishes astrocytes from other glial cells. Defects in GFAP are a cause of Ale, Xenopus/Amphibian,ander disease (ALE, Xenopus/Amphibian,D). Ale, Xenopus/Amphibian,ander disease is a rare disorder of the central nervous system. It is a progressive leukoencephalopathy whose hallmark is the widespread accumulation of Rosenthal fibers which are cytoplasmic inclusions in astrocytes.