[Neuropathology of tauopathy]

Microtubules are key cytoskeletal elements found in all eukaryotic cells. Tau was identified as microtubule associated protein and was implicated in microtubule initiation as well as assembly. Its expression is increased expression in neurons and has a specific association with axonal microtubules. Neurodegenerative disorders associated with abundant tau inclusions are collectively described as tauopathies. Pathological inclusions in neurons and glial cells containing fibrillary aggregates of abnormally hyperphosphorylated tau protein are characteristic features of tauopathies. We outlined the pathological features of major tauopathies, including neurofibrillary tangle formation diseases, Pick's disease (PiD), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and argyrophilic grain disease (AGD). Disease specific isoform compositions of tau are identified in these tauopathies. Neurofibrillary tangles (NFTs) in Alzheimer's disease contain both three repeat (3R)- and four repeat (4R)-tau. Pick bodies in PiD are immunopositive for 3R-tau. In PSP NFTs, tufted astrocytes, coiled bodies and threads contain 4R-tau and in CBD, pretangles, astrocytic plaques, coiled bodies and threads also demonstrate 4R-tau. Argyrophilic grains are immunopositive for 4R-tau. Although PSP and CBD sometimes share certain pathological distribution, which makes clinical diagnosis difficult, cellular tau pathology and aggregation patterns in neurons and glia are different between the two diseases.