microtubule-associated proteins that are mainly expressed in neurons. tau proteins constitute several isoforms and play an important role in the assembly of tubulin monomers into microtubules and in maintaining the cytoskeleton and axonal transport. Aggregation of specific sets of tau proteins in filamentous inclusions is the common feature of intraneuronal and glial fibrillar lesions (neurofibrillary tangles; neuropil threads) in numerous neurodegenerative disorders (alzheimer disease; tauopathies).