MAPT and tauopathy: Tau aggregates vary across the tauopathies (Table 1) with respect to (i) their isoform composition (3R vs. 4R); (ii) their accumulation in disparate cell types (e.g., neurons or astrocytes); (iii) their morphologies and ultrastructure (e.g., spherical Pick bodies vs. neuro-filamentous tangles in neurons; paired helical filaments vs. straight helical filaments); and (iv) their propensity to affect distinct brain regions [39].