April 24, 2026

7 min read

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How geneticists uncovered a common root of two neurological diseases

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) can have the same genetic cause, a discovery that won two neurogeneticists a portion of the 2026 Breakthrough Prize in Life Sciences

By Allison Parshall edited by Jeanna Bryner

Rosa Rademakers and Bryan Traynor attend the 12th Breakthrough Prize Ceremony on April 18, 2026 in Santa Monica, California

Vivien Killilea/Stringer/Getty Images

On the surface, frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are very different neurodegenerative diseases. In FTD, people can experience drastic changes in personality and behavior as neurons in the brain regions that control decision-making and language die off. ALS, on the other hand, frequently begins with muscle weakness and difficulty with swallowing and speech as people lose nerve cells that allow the brain to control the body.

“They’re two very clinically disparate syndromes,” says neurogeneticist Bryan Traynor of the National Institutes of Health, who studies ALS. As a doctor, “you would not mistake them.”

And yet these two disorders may have the same underlying causes, as Traynor and Rosa Rademakers, a neurogeneticist who studies FTD, and their respective colleagues discovered independently in 2011. Though most cases of ALS are “sporadic,” or apparently occurring without a family history, 5 to 10 percent come from genetic causes that are passed down through families. After four years of scouring the genomes of affected families for a responsible gene, Traynor and Rademakers identified a mutation of a gene called C9ORF72 that many people with a family history of both diseases share.

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Their research revealed that these two very different disorders are part of the same spectrum of disease, leading doctors and researchers to rethink these conditions and potential treatments. Last weekend, at a star-studded ceremony in Los Angeles, Rademakers and Traynor were awarded a portion of the 2026 Breakthrough Prize in Life Sciences for this discovery.

Scientific American spoke with them ahead of the awards ceremony about what happened during the yearslong search for this genetic mutation and how it has changed our understanding of these devastating diseases.

[An edited transcript of the interview follows.]

Take me back to the late 2000s. Why did you think that frontotemporal dementia and ALS were related?

RADEMAKERS: I come from the frontotemporal dementia field, and Bryan [comes] from the ALS field. And my history was on genetics of FTD and families, where some individuals had FTD, some had ALS or some even had both. I think we made the assumption that it would be possible that maybe there was one gene mutation in those families that could potentially give rise to both diseases. But you still have to find the gene to actually prove it. But Bryan, you come from a different perspective.

TRAYNOR: We had discovered mutations in a [different] gene that was a known cause of frontotemporal dementia, and we had found that mutations in that same gene also caused ALS. And it kind of sparked that interest in [asking], “Well, are these two separate conditions? How do they fit together?”

RADEMAKERS: Also, in the in the brains of patients with all sorts of dementia, you usually have a protein that sits in the brain and causes the brain cells to die. This is [true] for Alzheimer’s disease, for FTD, for Parkinson’s disease—but they’re different proteins. But a few years before our discovery, researchers found that the same protein [called TDP-43] is found in the spinal cords of patients with ALS and in the brains of patients with FTD. Maybe the same process could be underlying it, just [with] different areas of the body [being] affected.

How did you start looking for the responsible gene?

RADEMAKERS: We had already narrowed it down to chromosome 9—[many families with ALS or FTD] shared a piece of DNA on that chromosome that healthy individuals did not have. Bryan was at the NIH, and they had access to technologies that we didn’t. He reached out to me to say, “Hey, can we potentially also study the families that you've been working on?” Then we really worked together closely and tried this new method—which initially led to nothing.

In the initial pass of that data, we still didn't see [the mutation]. Usually, there’s one letter of the [genetic] code that's different, but that was not the case. Eventually, in our lab, we started focusing on the idea that it could be a special