ATP6AP2 and early-onset autosomal dominant Alzheimer disease: Functionally, ATP6AP2 plays important roles in multiple organs and cell types; and dysregulation of ATP6AP2 is implicated in the pathogenesis of numerous diseases, such as hypertension, pre-eclampsia, diabetic microangiopathy, acute kidney injury, cardiovascular disease, cancer, obesity, mental disorders (e.g., depression and post-traumatic stress disorder), and neurodegenerative diseases (e.g., Parkinson disease and Alzheimer disease).9,19–31 Notice that ATP6AP2 is abundantly expressed in bone cells, including OBs and OCs.