APP and early-onset autosomal dominant Alzheimer disease: The amino acid aggregates of Aβ peptides forming the major component of plaques characteristic of Alzheimer's Disease (AD) result from N-terminal cleavage of the amyloid precursor protein (APP) (Goedert and Spillantini, 2006) mediated by an aspartyl protease referred to as Beta-site APP Cleaving Enzyme 1 (BACE1) (Hussain et al., 1999; Sinha et al., 1999; Vassar et al., 1999; Yan et al., 1999).