The hallmark pathologies of AD are the extracellular accumulation of the processing products (Aβ42) of amyloid-β protein precursor (APP), which tend to aggregate forming beta-folded sheets, (amyloid plaques), and extracellular fibrillar aggregates of the microtubule-associated protein tau (neurofibrillary tangles), which are neurotoxic [5]. The gene discussed is APP; the disease is Alzheimer disease.