SPP1 and neurodegenerative disease: To understand the early-disease-enriched microglial populations, we visualized the microglial activation signature (CD74, SPP1, VIM, FTL, B2M) (APOE, TYROBP, CTSB) (C1QB and C1QC) as well a homeostatic signature (P2RY12, P2RY13, and OLFML3) on control-enriched and early-disease-enriched clusters from neurodegenerative diseases (Fig. 3E).