MIT researchers identify how APOE4 gene variant drives Alzheimer's risk through fat buildup in brain cells
A study reveals that APOE4 disrupts a cellular signaling pathway, causing lipid accumulation in oligodendrocytes and astrocytes—and suggests a potential drug target to reverse the damage.
What happened
Researchers at MIT, led by Li-Huei Tsai, published findings in Cell Stem Cell (October 15) identifying the mechanism by which APOE4—a gene variant that increases Alzheimer's risk threefold to twelvefold—causes disease. Using stem cells and genetic screening, the team found that APOE4 disrupts the Wnt signaling pathway in oligodendrocytes (cells that insulate neuron connections), leading to cholesterol and fat droplet accumulation. The researchers identified DKK1, a key brake gene in this pathway, and showed that disabling it reduced fat droplets in lab cells. In mouse models, blocking an enzyme that breaks down Wnt signaling proteins restored normal signaling, reduced fat buildup, and improved myelin formation and cognitive performance. Analysis of brain tissue from APOE4-carrying organ donors confirmed signs of low Wnt signaling.
Context
Alzheimer's disease research has historically centered on amyloid-beta and tau protein accumulation, but recent work has identified lipid (fat) buildup as a third pathological mechanism. APOE proteins normally transport fats throughout the body and brain, but the APOE4 variant performs this function less efficiently. The study's identification of the Wnt signaling disruption as the driver of fat accumulation opens a potential new therapeutic avenue—targeting lipid clearance rather than only amyloid and tau. Researchers note that APOE4 may affect multiple cell types and processes beyond lipids, including blood vessel support and protein degradation in astrocytes, suggesting multiple dysfunction points across the brain. This work supports an emerging consensus in the field that effective Alzheimer's treatment will likely require multiple drugs targeting different pathological elements.
What's disputed
The findings have not yet been confirmed in human subjects. Researchers acknowledge the need for further investigation into how lipid-targeting approaches could be safely and effectively applied in humans.