MAPT and tauopathy: Many studies suggest that tau oligomers (soluble and intermediate tau aggregates) but not neurofibrillary tangles (NFTs) formed by the deposition of aggregated tau are the main toxic tau species in tauopathies [23, 27], and systemic administration of TOMA reversed neurodegenerative phenotypes in the brain of aged P301L tau transgenic mice [9, 10, 22].