KAT5 and Alzheimer disease: However, Tat-interacting 60 kDa protein (TIP60/KAT5, a HAT for expression of H3K9ac, H3K14ac, and H2AK5ac) was significantly reduced in both neurons and glial cells and largely absent from nuclei of neurons in the AD hippocampus 238, where TIP60 and GCN5/KAT2A were usually most strongly expressed 239-241, suggesting that H3K9ac and other acetylated histones catalyzed by TIP60, were decreased in the AD hippocampus.