APP and Alzheimer disease: IPSC-derived neurons display many of the cellular phenotypes found in AD patients which are associated with amyloid precursor protein (APP) [29], presenilin [30], or SORL1 mutation [31], which are involved in amyloid precursor protein processing; dysfunction of these proteins could lead to impaired γ-secretase activity, endoplasmic reticulum and oxidative stress with tau protein hyperphosphorylation, and amyloid β peptide (Aβ) accumulation.