Alzheimer’s disease (AD) is a progressive neurological disease that causes impairments in memory and cognition. AD is believed to result from the deposition of protein “plaques” consisting of amyloid beta (Aβ) proteins sequentially generated via the enzyme γ-secretase. Although most cases of AD are sporadic or late-onset, early-onset or familial AD (FAD) caused by mutations in genes encoding γ-secretase is also noted. Differences in the sequential processing of Aβ proteins between sporadic AD and FAD have so far remained unclear.