Although astrocytes are the major source of apoE production in brains1,7, neurons can also produce apoE, especially under stress or in response to injuries1,7,31–33. We confirmed that hiPSC-derived neurons, including glutamatergic and GABAergic neurons, did express apoE in culture (likely represents a “stress” condition) as determined by anti-apoE and anti-neuronal marker double immunostaining (Supplementary Fig. 11). Since our neuronal culture is highly pure, with negligible astrocytes (Supplementary Fig. 12a,c,e), the neuronal apoE is unlikely taken up from astrocyte-secreted pool.
