MAPT and Alzheimer disease: Three-dimensional organoids and three-dimensional hippocampal spheroids composed of AD iPSC-derived neural cells also showed increased levels of p-tau, Aβ pathology and synaptic dysfunction, the latter of which is an early feature of AD pathology (Raja et al., 2016; Gonzalez et al., 2018; Lin et al., 2018; Pomeshchik et al., 2020; Zhao et al., 2020).