A Colombian man carried one of the most aggressive genetic mutations known to cause early-onset Alzheimer’s disease. By all expectations, he should have developed dementia around age 45. Instead, he remained cognitively sharp into his early 70s, outlasting the typical timeline by nearly three decades. When researchers finally identified what set him apart, the answer came down to a single rare variant of a protein called Reelin.
The case, published in Nature Medicine by a team led by neurologist Francisco Lopera of the University of Antioquia and researchers at Harvard and the Schepens Eye Research Institute, has since become one of the most closely studied observations in Alzheimer’s research. As of mid-2026, it continues to shape how scientists think about resilience to the disease and whether that resilience can be replicated therapeutically.
A man who defied his own genetics
The patient belonged to a large extended family in Antioquia, Colombia, that carries the PSEN1-E280A mutation. This mutation is one of the best-characterized causes of autosomal dominant Alzheimer’s. Among carriers, cognitive decline typically begins around age 44, and dementia follows within a few years. The kindred, numbering roughly 6,000 people, has been tracked by Lopera’s group for decades and has contributed enormously to the understanding of early-onset disease.
This particular man did not show signs of mild cognitive impairment until approximately age 72. Genetic sequencing revealed he was heterozygous for a missense mutation at position H3447R in the RELN gene, a variant the researchers designated RELN-COLBOS. The name honors Colombia and Boston, the two research hubs behind the discovery.
Crucially, his brain was not free of Alzheimer’s pathology. Neuroimaging and, after his death, neuropathological examination confirmed extensive amyloid plaques and tau tangles. The disease process had advanced at a molecular level. But certain regions of the medial temporal lobe, areas critical for memory, showed relatively preserved structure compared with what would be expected in a typical PSEN1-E280A carrier of his age. The distinction matters: RELN-COLBOS did not prevent plaque formation. It appeared to blunt the downstream destruction those plaques normally cause.
How Reelin protects neurons
Reelin is a large signaling protein expressed in brain regions that Alzheimer’s strikes earliest, including the entorhinal cortex. Under normal conditions, Reelin binds to two lipoprotein receptors on neurons, ApoER2 and VLDLR, which then activate an intracellular adaptor protein called Dab1. This cascade supports synaptic plasticity, the ability of neurons to strengthen or adjust their connections, and intersects with ApoE biology, a well-known factor in amyloid processing.
Research in transgenic mouse models and human brain tissue has shown that Reelin levels decline in areas affected by amyloid-beta accumulation. That depletion tracks with neuronal damage, suggesting that losing Reelin leaves neurons more exposed to the toxic effects of plaques.
In the Colombian patient, laboratory experiments indicated that RELN-COLBOS acts as a gain-of-function variant. Cell-based assays showed stronger activation of the Dab1 signaling cascade compared with the typical form of Reelin. The heightened signaling may help stabilize synapses and maintain neuronal communication even under heavy amyloid and tau burden. After death, neuropathological analysis confirmed that while plaques and tangles were abundant, some brain regions expected to be severely damaged showed milder neuronal loss than predicted.
A separate line of research has reinforced the importance of this receptor pathway. Studies have demonstrated that increasing ApoER2 levels through genetic manipulation reduces amyloid accumulation in animal models, supporting the broader idea that boosting Reelin-related signaling can shift the balance against plaque-driven damage.
He was not the first resilience case
The RELN-COLBOS finding is the second major resilience case to emerge from the Colombian kindred. In 2019, a separate team reported in Nature Medicine on a woman from the same family who also carried the PSEN1-E280A mutation but did not develop dementia until her late 70s. Her protection was traced to a different mechanism: she was homozygous for a rare variant of APOE3 known as the Christchurch mutation, which appeared to limit tau pathology in key brain regions even as amyloid accumulated extensively.
Together, the two cases suggest that the brain has more than one potential route to resilience against Alzheimer’s pathology. One operates through ApoE and tau; the other through Reelin and synaptic maintenance. Both cases involved lifelong genetic variants present from conception, raising the question of whether interventions introduced later in life could achieve similar results.
What scientists still do not know
The most significant limitation is that the strongest evidence for RELN-COLBOS comes from a single patient. One person’s extraordinary trajectory, however thoroughly documented, does not prove the variant would protect others. The PSEN1-E280A kindred is genetically distinctive, and the interaction between RELN-COLBOS and that specific mutation may not translate to the sporadic forms of Alzheimer’s that account for the vast majority of cases worldwide.
Whether Reelin actively promotes clearance of plaques, shields neurons from their effects, or does both remains unresolved. The headline framing of “cleaning out” plaques reflects the therapeutic aspiration, but the published evidence more directly supports a model of tolerance: the brain enduring pathology rather than eliminating it.
There are also open questions about genetic interactions. The ApoE4 allele, the strongest common genetic risk factor for Alzheimer’s, drives increased amyloid deposition and earlier symptom onset. Whether enhanced Reelin signaling would hold up in ApoE4 carriers, or whether certain variant combinations might cancel each other out, has not been tested.
Proteomic studies of Alzheimer’s brains have added another layer of complexity. A 2024 analysis published in Nature Neuroscience mapped networks of proteins that track with amyloid plaque and tau tangle progression, including microglial immune response modules and protein metabolism pathways. Those findings suggest Reelin operates within a broader system of interacting proteins, complicating any single-target drug strategy.
No human clinical trial has tested a Reelin-enhancing therapy. The gap between a protective genetic variant found in one person and a drug or gene therapy that could replicate its effects in millions of patients involves enormous scientific and regulatory hurdles. Researchers have not outlined a clinical pathway, and no pharmaceutical company has publicly announced a Reelin-focused program for Alzheimer’s.
Where this fits alongside current treatments
The Reelin findings arrive at a moment when the Alzheimer’s field is already grappling with the limits of its leading therapeutic strategy. Anti-amyloid antibodies such as lecanemab (marketed as Leqembi) and donanemab have demonstrated the ability to clear amyloid plaques from the brain, and both have received regulatory attention. But their clinical benefits have been modest, slowing cognitive decline by roughly 25 to 35 percent in trials, and they carry risks of brain swelling and microbleeds.
The RELN-COLBOS case raises a different possibility: rather than removing plaques, it may be possible to make the brain more tolerant of them. If Reelin signaling can preserve synaptic function and delay neuronal death even when amyloid and tau are present, a Reelin-based approach could complement plaque-clearing drugs or offer an alternative for patients who cannot tolerate them.
That remains speculative. But the Colombian case has given researchers a concrete molecular target and a biological rationale that few single-patient observations in Alzheimer’s history have provided.
What comes next for Reelin research
Several research directions are now in motion. Scientists are searching for additional individuals who carry RELN-COLBOS or similar gain-of-function Reelin variants, which would help determine whether the protection is reproducible. Animal studies are testing whether boosting Reelin signaling in models that more closely mimic human Alzheimer’s can delay cognitive decline. And mapping how the Reelin pathway intersects with ApoE biology, microglial function, and tau propagation will be essential before any human trial could be designed.
Timing is another unresolved variable. The Colombian man carried his protective variant from birth, meaning Reelin signaling shaped his brain development and circuit formation over a lifetime. A therapy introduced in midlife or after symptoms appear might not reproduce the same degree of resilience. Whether there is a window in which intervention could still make a meaningful difference is one of the most important questions the field now faces.
For now, the RELN-COLBOS story stands as one of the most compelling clues in Alzheimer’s research: a single protein variant that gave one man decades of cognitive life he was never expected to have. Translating that clue into something that helps the roughly 55 million people living with dementia worldwide will require years of work. But the direction it points, toward resilience rather than just removal, may ultimately reshape how scientists and physicians think about fighting this disease.
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*This article was researched with the help of AI, with human editors creating the final content.
