Alzheimer's disease (AD) is characterized by progressive cognitive decline associated with the accumulation of amyloid-β (Aβ) peptides and dysregulation of β-site amyloid precursor protein-cleaving enzyme (BACE1) and its phosphorylation at T252 (P-BACE1-T252) as well to the kinase's expression and activity. The gene discussed is BACE1; the disease is early-onset autosomal dominant Alzheimer disease.