A recent publication by Arakhamia et al. compared cryo-EM structures and posttranslational modifications present on tau filaments purified from brains of patients with AD (9) and corticobasal degeneration (CBD) (10) showing that acetylation was found mostly within the fibril-forming core and was predicted to favor β-strand stacking and make tau less soluble (4). Here, MAPT is linked to Alzheimer disease.