12 Mar 2021 The E4 allele of the apolipoprotein E, a strong risk factor for many neurodegenerative diseases, most prominently late-onset Alzheimer’s disease, upsets the balance of lipids within cells. Exactly how ApoE4 does this remains unclear. In the March 3 Science Translational Medicine, researchers led by Li-Huei Tsai at MIT found that in human astrocytes and microglia, ApoE4 increased the amount of unsaturated lipids, which then accumulated in lipid droplets. Adding the phospholipid precursor choline to the cells restored their normal lipid metabolism, hinting at potential therapeutic approaches for ApoE4 carriers. How exactly does ApoE4 lead to lipid imbalance in astrocytes?