MAPT and Alzheimer disease: P21-activated kinase 1, encoded by the PAK1 gene, has been implicated in AD [52], and recent studies have revealed that inactivation of PAK1 obliterated social recognition without changing amyloid beta (Aβ)/tau pathology, and also exacerbated synaptic impairment and behavioral deficits in mouse models of AD [53, 54].