Single‐cell RNA sequencing identified astrocytes, oligodendrocytes, endothelial cells, and microglia as the cell types most impacted by the apoE ε4 to apoE ε2 “switch.” Each of these cell types has differentially expressed genes that have been associated with AD‐related pathways, particularly pathways involved with lipid and carbohydrate metabolism. The gene discussed is APOE; the disease is Alzheimer disease.