THE ARISING · Longevity & Healthspan
How the APOE4 Alzheimer's Gene Disrupts Brain Insulation, and a Possible Fix
The APOE4 gene variant is the strongest genetic risk factor for lateonset Alzheimer's disease, yet how it raises risk has stayed unclear. A new study points to one pathway: fat build-up in the brain cells that make the insulation around nerve fibres, and an enzyme that might be switched down to reverse it.
This is early laboratory work. According to the paper in Cell Stem Cell (2026), the team used oligodendrocytes grown from human induced pluripotent stem cells, three-dimensional brain organoids, and a mouse model carrying APOE4 and a human tau mutation (called APOE4;PS19). No people were treated.
Oligodendrocytes are the cells that wrap nerve fibres in myelin, a fatty coating that helps signals travel between neurons. The same group had previously found that APOE4 causes lipid droplets, small stores of fat, to build up in these cells, and that myelination falls as a result. What drove the build-up was unknown.
To find out, the researchers ran a genome-wide CRISPR screen in the human cellderived oligodendrocytes. They also mapped which stretches of DNA were open and accessible, using a method called ATAC sequencing. Together, these pointed to two linked findings: reduced Wnt signaling and overactive glycogen synthase kinase-3 beta, or GSK3B. Both were identified as key regulators of lipid-droplet build-up.
The team then tested blocking GSK3B, both genetically and with drugs. In APOE4 oligodendrocytes, this reduced lipid droplets. In brain organoids, it increased myelination. In the APOE4;PS19 mice, a drug that inhibits GSK3B also reduced lipid droplets and improved myelination.
The authors describe this as a mechanistic framework linking Wnt/GSK3B signaling to APOE4-driven disruption of fat handling and myelination. They call GSK3B a potential therapeutic target. That is the study's own, cautious wording.
The press coverage adds some detail. Fight Aging!, which summarised the work, names the compounds used: CHIR99021 to inhibit GSK3B and Dif3 to raise it. It also reports that APOE4 cells had less beta-catenin, a protein that promotes Wnt signaling, and more GSK3B than APOE3 cells. It says axon growth rose in the organoids. We could not check those points against the full paper. The coverage also says Wnt signaling was restored, whereas the study describes inhibiting GSK3B.
What does this mean for people who carry APOE4? Mainly, it offers a possible explanation for how the variant affects the brain, beyond the inflammation-focused ideas that have dominated. It does not show that myelin loss causes Alzheimer's in people, and it does not show that any GSK3B-blocking drug is safe or effective in humans. Results in cells and mice often fail to carry over to patients.
The next things to watch are whether the full paper details safety and dosing in animals, whether similar myelin and lipid changes are confirmed in people who carry APOE4, and whether any GSK3B-targeted treatment reaches human trials.