HIF1A and Alzheimer disease: Mi_6 was enriched in aged E4 mice (12.9% of all microglia) relative to E3 (6.1%) (Figure 2E; Figures S4A and S4B), and a pathway analysis of the Mi_6 biomarkers highlighted “Alzheimer’s disease” and metabolic pathways including “cholesterol metabolism” and “HIF1 signaling” (Figure 2F).