Although D-serine supplementation did not enhance astrogliosis in APPKI mice at 12 months of age (Supplementary Figure 3), possibly due to a ceiling effect, APPKI-SRRKO mice exhibited lower GFAP expression than APPKI mice at 9 months of age (Figures 4C, D and Supplementary Figure 4), again suggesting that D-serine influences astrogliosis during AD progression by promoting excessive NMDAR activity. Here, GFAP is linked to Alzheimer disease.