A rare form of the APOE gene associated with longer life and lower Alzheimer’s risk may protect neurons by limiting DNA damage and helping them recover from cellular stress, according to a study highlighted on Friday, July 24. Researchers at the Buck Institute for Research on Aging said the laboratory findings offer a possible explanation for APOE2’s long-observed protective association, while stopping well short of showing a treatment for patients.
The peer-reviewed study, published in the journal Aging Cell, compared the three common gene variants APOE2, APOE3 and APOE4. APOE4 is the strongest known genetic risk factor for late-onset Alzheimer’s disease, whereas population research has repeatedly associated APOE2 with reduced dementia risk and exceptional longevity. The biological mechanism behind that difference has remained uncertain.
Researchers used human induced pluripotent stem cells engineered to differ only at the APOE locus, then converted them into inhibitory GABAergic neurons and excitatory glutamatergic neurons. They also examined hippocampal tissue from older mice engineered to carry human APOE variants. RNA sequencing and direct measurements of DNA strand breaks showed less damage and stronger activation of repair and damage-response pathways in APOE2 neurons than in comparison cells.
The team exposed excitatory neurons to radiation or doxorubicin, stresses that can damage DNA. Cells carrying APOE2 showed lower levels of the senescence markers p16 and CRYAB, smaller nucleoli and better-preserved nuclear structure than cells carrying APOE3 or APOE4. Older APOE2 mice likewise showed features linked to healthier cellular aging in the hippocampus, including better-preserved heterochromatin and higher levels of the structural protein Lamin A/C.
In another experiment, adding recombinant APOE2 protein to APOE4 neurons reduced DNA-damage signaling after radiation. The researchers said this suggests that part of the protective effect might be transferable, rather than available only to people born with APOE2. However, the work involved cultured cells and genetically engineered mice; it did not test whether an APOE2-based medicine prevents dementia or improves outcomes in humans.
The study broadens research on APOE beyond its established roles in lipid transport and amyloid biology, connecting the gene to genome maintenance and cellular senescence. The investigators said they still do not know precisely how APOE2 stabilizes the nuclear envelope or strengthens DNA repair. Future work will examine APOE2-mimicking compounds and targeted repair strategies, particularly for APOE4 carriers, with extensive safety and human testing required before any clinical use.
Comments