PTPA and early-onset autosomal dominant Alzheimer disease: PP2A heterotrimers play critical roles in diverse signaling pathways including regulation of the cell cycle, cell proliferation, and neuronal signalling, and deficits in PP2A function are implicated in many human diseases including cancer, Alzheimer’s disease and major depressive disorder (Sontag and Sontag, 2014; Network and Pathway Analysis Subgroup of Psychiatric Genomics Consortium, 2015; Sangodkar et al., 2016).