ALDH1L1 and Alzheimer disease: In order to study the role of astrocyte-derived APOE on amyloid plaque pathology, we expressed the different human APOE isoforms (further referred to as APOE2, APOE3 and APOE4), along with reporter mCherry protein, specifically in astrocytes in an Apoe-deficient AD mouse model (AppNL-G-F x Apoe−/−), using recombinant AAV2/8 particles (injected ICV at postnatal day 2/3, see Methods for details) and the astrocyte specific promoter ALDH1L1 (Fig. 1A).