APOE and Alzheimer disease: These platforms can be used to model the risk or protective effect of common APOE isoforms, including APOE2, APOE3, and APOE4, and other rare APOE variants, including the APOE3-Jacksonville (V236E) variant and the APOE4-R251G variant.1,20 In this study, we have demonstrated that the APOECh variant is causal to neuroprotection, extending the observation made in the 2019 single-patient study21 and providing strong rationale for developing potential AD therapies by targeting the protective APOECh variant and using the APOECh variant-carrying cells.