KAT5 and early-onset autosomal dominant Alzheimer disease: Tip60 HAT activity has been implicated in the age-related neurodegenerative disorder Alzheimer's disease (AD) via its HAT dependent complex formation with the C-terminal fragment of the amyloid precursor protein (APP) known as the APP intracellular domain (AICD) and linker protein Fe65 [22], [55], [56], [57].