Proteolysis of the single pass trans-membrane protein APP (Amyloid Precursor Protein) leads to the generation of Aβ (beta amyloid), a 40 or 42 amino acid peptide that is the main constituent of the amyloid plaques found in the brains of people with Alzheimer's disease [1]. The gene discussed is APP; the disease is early-onset autosomal dominant Alzheimer disease.