MAPT and Alzheimer disease: In this study, we investigated the association between DARPP-32 and CREB malfunction in AD pathology and found cleavage of DARPP-32 in AD brain tissue and neuronal cells treated with Aβ or okadaic acid (OA), a protein phosphatase-2A (PP2A) inhibitor that induces tau hyperphosphorylation and neuronal death in vitro (Yoon et al., 2012).