Induced pluripotent stem cells (iPSCs) were created from human fibroblasts (S1 Table). Two of the iPSC lines carrying duplications in the gene for Amyloid Precursor Protein (APP; APPDp1-1 and APPDp2-3) were provided by Dr. Lawrence Goldstein at the University of California, San Diego, and have been described previously [44]. One control iPSC line (AG09173) was kindly provided by Dr. Bruce A. Yankner at McLean Hospital and Harvard Medical School. The other lines were generated from fibroblasts at the Picower institute of Learning and Memory, iPSC core facility at the Massachusetts Institute of Technology (MIT) using Sendai virus to overexpress OCT4, SOX2, KLF4, and c-MYC. S1 Table. details the sources and attributes of the cells used in this study. Pluripotency was confirmed by immunocytochemistry for TRA-1-81 and TRA-1-60 (S1 Fig). All reagents were purchased from Life Technologies Corporation, Grand Island, NY, unless mentioned otherwise. iPSCs were cultured on irradiated mouse embryonic fibroblasts (MEFs, MTI-GlobalStem, Gaithersburg, MD) in DMEM/F12 media supplemented with knockout serum replacement (KSR, 20% v/v), non-essential amino acids (NEAA-1X), GlutaMAX (1X), beta-Fibroblast Growth Factor (FGF2, PeproTech, Inc, Rocky Hill,
