APP and Alzheimer disease: AD iPSC-derived neurons carrying mutations in APP, PSEN1 or PSEN2 show an increased production of Aβ or an increased Aβ42/ Aβ40 ratio, as well as elevated levels of total tau and phosphorylated tau (p-tau), which accumulates in neurofibrillary tangles (Muratore et al., 2014; Ortiz-Virumbrales et al., 2017; Yang et al., 2017; Qu et al., 2023).