Longevity-linked APOE2 gene variant helps neurons repair DNA and resist aging

Research from the Buck Institute reveals that the protective APOE2 variant, already associated with exceptional longevity and reduced Alzheimer's risk, keeps human brain cells genomically stable and resistant to cellular senescence

People who carry the APOE2 version of the apolipoprotein E gene are more likely to live to advanced age and are partly protected against Alzheimer's disease, but scientists have struggled to explain why. A new study from the Buck Institute for Research on Aging, now published in Aging Cell, offers a mechanistic answer: APOE2 helps human neurons keep their DNA intact and resist becoming senescent, a damaged, dysfunctional state that accumulates with age and contributes to neurodegeneration.

The findings shift attention away from APOE's well-known role in cholesterol transport and toward a previously underappreciated function of the gene: shaping how brain cells maintain the integrity of their genome as they age.

Lisa Ellerby, PhD

“We've known for years that APOE2 carriers tend to live longer and have a lower risk of Alzheimer's, but the protective mechanism has been a black box,” says senior author Lisa M. Ellerby, PhD, professor at the Buck Institute. “Our work shows that APOE2 neurons are better at preventing and repairing DNA damage, and they resist the cellular aging program that drives so much of late-life decline. Our findings point to entirely new therapeutic directions.”

What the researchers did

APOE comes in three common forms, APOE2, APOE3, and APOE4, that differ by just two amino acids. APOE4 is the strongest known genetic risk factor for late-onset Alzheimer's disease (typically after age 65), while APOE2 is consistently linked in population studies to exceptional longevity and reduced dementia risk.

To isolate what APOE itself contributes to neuronal aging, the Buck team used human induced pluripotent stem cells (iPSCs) genetically engineered to differ only at the APOE locus. They generated two types of brain neurons from these cells, inhibitory GABAergic neurons and excitatory glutamatergic neurons, and compared how the different APOE versions affected each cell type. They also examined hippocampal tissue from aged mice carrying the human APOE2, APOE3, or APOE4 gene.

Key findings

APOE2 neurons accumulate less DNA damage. Bulk and single-cell RNA sequencing showed that APOE2 GABAergic neurons strongly upregulate DNA repair and damage-response pathways, while APOE4 neurons show transcriptional signatures associated with Alzheimer's disease. Direct measurements of DNA strand breaks confirmed that APOE2 neurons carried significantly less damage.

APOE2 neurons resist becoming senescent. When the team stressed excitatory neurons with radiation or the chemotherapy drug doxorubicin, APOE2 neurons showed lower levels of senescence markers (including p16 and CRYAB), smaller nucleoli, and better-preserved nuclear architecture compared with APOE3 and APOE4 neurons.

APOE2 protein can protect APOE4 neurons. Adding recombinant APOE2 protein to APOE4 neurons reduced DNA damage signaling after radiation, an early hint that the protective effect might be transferable, not just genetic.

The mouse brain agrees. Aged APOE2 knock-in mice showed smaller nucleoli, higher levels of the nuclear scaffolding protein Lamin A/C, and better-preserved heterochromatin in the hippocampus than APOE3 or APOE4 mice, features associated with healthier brain aging.

Why it matters

Cellular senescence and accumulated DNA damage are now recognized as central drivers of aging and age-related disease, including Alzheimer's. “Until now, the APOE field has focused largely on lipid handling and amyloid-beta biology,” says Ellerby. “By showing that APOE alleles also tune how neurons defend their genome, this study connects a major longevity gene to two of the most actively studied hallmarks of aging.”

Ellerby says the work suggests that strategies aimed at boosting DNA repair or clearing senescent cells in the brain could mimic some of the natural protection conferred by APOE2, potentially benefiting people who carry the higher-risk APOE4 variant.

Cristian Gerónimo-Olvera, PhD

“What surprised us was how consistent the picture was across two very different neuron types and across human cells and mouse brain tissue,” said co-first author Cristian Gerónimo-Olvera, PhD, a postdoctoral fellow at the Buck Institute. “APOE2 neurons aren't just less damaged at baseline, they recover faster when stressed.”

Next steps

The authors note that the precise molecular mechanism by which APOE2 stabilizes the nuclear envelope and supports DNA repair remains to be defined. Future studies will explore whether APOE2-mimetic compounds or targeted DNA repair therapies can confer similar protection in APOE4 carriers, the population at highest genetic risk for Alzheimer's disease.

Citation: “Exceptional Longevity Modifying Allele APOE2 Promotes DNA Signaling Pathways Resisting Cellular Senescence in Human Neurons.”

DOI: 10.1111/acel.70494

Other collaborators include:
Stephen M. Scheeler, Carlos Galicia Aguirre, Genesis Vega-Hormazabal, Daniela Garcia, Long Wu, Natalia Murad, Kevin Schneide, Kenneth A. Wilson, Nikola T. Markov, | Jesse Simons, Akos A. Gerencser, Emily Parlan, Eric Verdin, Judith Campisi, Tara E. Tracy, David Furman, Simon Melov, Buck Institute; Sicheng Song and Sean D. Mooney, Department of Biomedical Informatics and Medical Education, University of Washington, Seattle, Washington

Acknowledgements:

This work was supported by the National Institute on Aging (R01AG061879, P01AG066591, T32 AG000266), the Paul F. Glenn Center for Biology of Aging, the Hevolution Foundation (HF-PART-23-1422047), and a CatalystX award from Alex and Bob Griswold and the Valley Foundation Fellowship.

The image in the header is an artistic representation of how APOE2 promotes resilience to cellular senescence maintaining the integrity of DNA and the nuclear envelope. We show a neuron protected by APOE2 represented as orange dots across the cell, with a blue mesh representing the resistance to senescence. We highlight in golden the integrity of the nucleus and the protected genome.