ASCL1 and Alzheimer disease: To prepare AD patient iNs that express APOE ε4 at the amyloid-seeding and amyloid-aggregation stages, fibroblasts of AD patients harboring presenilin mutations were transduced with lentivirus constitutively expressing Ascl1, Brn2, and Myt1l (ABM) along with doxycycline-inducible APOE ε4 lentivirus (Fig. 1a).