Variant A673T, corresponding to a single nucleotide alanine-to-threonine substitution adjacent to the β-secretase (BACE1) site in APP, was markedly more common in the elderly control than in the AD subjects; this is consistent with an ≈ 40% reduction in the Aβ, formation observed in vitro (42). The gene discussed is BACE1; the disease is Alzheimer disease.