Rare Gene Variant May Explain Why Some High-Risk Carriers Avoid Alzheimer's Damage

A Columbia University study in Nature Aging shows how a protein called fibronectin, which builds up abnormally in people who carry the Alzheimer's risk gene APOE4, damages brain blood vessels, and how a rare genetic variant already tied to resistance in APOE4 carriers appears to work by limiting that buildup.

Researchers at Columbia University Irving Medical Center reported on September 11, 2026, in the journal Nature Aging, that a structural protein called fibronectin builds up abnormally around brain blood vessels in people who carry the APOE epsilon4 gene, and that this buildup actively damages the blood-brain barrier, the system that controls what passes from the bloodstream into the brain. The team, led by Caghan Kizil, combined postmortem brain tissue from 23 people, single-nucleus sequencing of more than 400,000 brain cells, lab-grown human vascular models, and experiments in zebrafish and in mice carrying the human APOE4 gene. Mice with the human APOE4 variant had nearly double the fibronectin levels in the brain compared with mice carrying the more common APOE3 variant, along with signs of a leakier barrier; reducing fibronectin or restoring the growth-factor signaling it disrupts restored barrier function in the cell and animal models.

APOE epsilon4 is the strongest common genetic risk factor for Alzheimer's disease, carried by roughly one in five people, yet some carriers remain cognitively healthy into their eighties. In 2024, the same Columbia group, writing in Acta Neuropathologica, reported that a rare coding variant in the fibronectin gene, FN1, was associated with lower Alzheimer's risk (odds ratio 0.29) and an average age of onset about 3.4 years later among APOE4 carriers, based on genome sequencing of 2,430 people age 60 and older drawn from three federally funded research cohorts. The new Nature Aging paper does not report new figures on that genetic association; instead it maps the biological steps between APOE4 and barrier damage that the rare variant appears to interrupt, identifying fibronectin as what the authors call a proximal mediator of the vascular dysfunction linked to APOE4.

The findings point to fibronectin, and the pathway it disrupts, as a possible target for future drugs intended to protect the brain's vasculature in Alzheimer's disease. But the study is mechanistic research built from postmortem tissue, cell cultures, zebrafish and mice, together with observational human genetic data; it is not a clinical trial, and no treatment, test, or dosing guidance has resulted from it.

"This new study takes us from a genetic clue to a disease mechanism," said Kizil, a professor of neurological sciences at Columbia's Vagelos College of Physicians and Surgeons, in a statement accompanying the paper. Whether a drug that mimics the rare variant could help people who do not carry it remains untested, the researchers said.