APP and osteoporosis: Furthermore, mutations in the genes encoding amyloid precursor protein, presenilin 1, and presenilin 2 are responsible for early-onset autosomal-dominant Alzheimer disease.15 One of the functions of amyloid precursor protein is related to the suppression of osteoblastogenesis and bone formation,60 implicating amyloid precursor protein as a risk factor of osteoporosis and bone fracture.