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A group of researchers at the University of Pennsylvania, USA, has recently carried out an investigation to explore whether using a type of talking therapy, called Acceptance and Commitment Therapy (ACT), can help improve the mental wellbeing of people affected by Huntington’s disease (HD). The study, published in the Journal of Huntington’s Disease, combines a short review of earlier work on ACT with the detailed report on a person with HD who underwent an online caregiver-assisted ACT programme. The results showed promising effects of ACT on a number of psychological difficulties in both the person with HD and his caregiver.

Psychological Difficulties in HD

HD is associated with a heavy psychological load. Alongside the well-known movement and cognitive problems, people with HD often face psychological difficulties such as depression, anxiety, irritability, apathy, emotional dysregulation, obsessions, and ‘perseverative’ behaviours (i.e., getting stuck on the same thoughts or actions). These issues can be experienced even years before the onset of movement problems (i.e., at the ‘premanifest’ stage, HD-ISS stage 0) and have been linked with a risk of suicide which is two to seven times higher than in the general population. Growing up within an HD family has also been linked to increased experiences of childhood trauma.

In addition, since HD is inherited, taking a predictive genetic test can be exceptionally stressful from a psychological perspective and lead to difficult family dynamics, which may explain why less than one in four persons at risk worldwide choose to get tested. At the same time, caregivers of people with HD – often represented by partners, relatives, or friends – may also experience several psychological difficulties, including burnout, anxiety, depression, as well as social issues such as stigma and isolation.

What Support Can HD Families Get?

Although access to psychological support is often mentioned as a top priority by HD families, the current landscape of psychological interventions for this population is extremely limited, with very few studies carried out so far and no gold-standard recognised approach. In addition, the availability of psychological support tends to vary dramatically both between countries as well as even within the same country, as specific regions may have fewer opportunities and resources.

This limited availability is perhaps unsurprising when we consider how emotional and behavioural difficulties in people with HD have been traditionally seen under a purely biomedical lens, which means that common issues such as high levels of anxiety and low mood are often considered a consequence of brain degeneration, and not a reflection having to adjust to the fact that, you know, having HD really sucks. 

What is Acceptance and Commitment Therapy (ACT)?

Acceptance and Commitment Therapy (ACT) is a modern form of psychotherapy which, in a nutshell, aims to help people make room for difficult thoughts and feelings while moving towards what matters most to them. The approach is based on six main principles/skills:

1. Acceptance: making room for tough feelings instead of fighting them.
2. Defusion: noticing thoughts and separating oneself from them.
3. Being Present: paying attention to what is happening right now, without ‘replaying’ the past or jumping to the future.
4. Self-as-Context: remembering that one may have thoughts and feelings but is not defined by them.
5. Values: knowing what kind of person one wants to be and what matters to them.
6. Committed Action: taking small, steady steps that match one’s values, even when feelings are tough.

These skills are often taught and practised through metaphors and short exercises which can be carried out in person or virtually, as well as in one-on-one or group therapy sessions. 

Crucially, unlike some other forms of psychotherapy such as traditional Cognitive Behavioural Therapy (CBT), ACT does not ask people to challenge sad or difficult thoughts or to prove them wrong, but rather to change their relationship with them. This is particularly helpful for individuals affected by HD, as it acknowledges and respects the genuine losses, fears, and worries associated with the condition. 

A Review of Earlier ACT Work

ACT was developed in the late 1980s by the American psychologist Steven C. Hayes as an evolution of traditional Cognitive Behavioural Therapy (CBT). Since then, over 900 randomised trials have investigated the efficacy of this approach, including one from the World Health Organisation (WHO), which now formally distributes it as a form of therapy. 

ACT has shown benefits in tackling depression, anxiety, suicidality, and substance misuse across several chronic conditions – such as cancer, obesity, hearing loss, and chronic pain – as well as neurodegenerative illnesses more akin to HD, including Parkinson’s, multiple sclerosis, and amyotrophic lateral sclerosis. Despite this, no formal exploration of ACT with people with HD had been published until this study.

The Case Report

A 52-year-old white American man (whom we shall call ‘Alan’ in this article), living with HD as well as bipolar and obsessive-compulsive issues, was invited by the authors’ US clinic to undergo a six-session ACT programme adapted from earlier work in other chronic conditions (e.g., HIV, cystic fibrosis, and cancer). All meetings took place online between May and June 2022. Alan attended these alongside his ex-wife, who was also his main caregiver and close friend. Her presence was found to be especially helpful in calming Alan’s anxiety and facilitating exercises and homework between sessions. 

Each session was inspired by one of ACT’s six core principles/skills: 

Session 1 helped the pair list their top five values and notice obstacles – what did Alan stand for and what got in his way?

Session 2 introduced acceptance through metaphors showing how struggling to control feelings can make things worse – e.g., how did Alan try to avoid or push away anxiety, depression, and worries about HD?

Session 3 focused on committed actions – what small, yet consistent moves towards values could Alan take even on bad days?

Session 4 taught present-moment awareness and normalised acceptance of painful thoughts – how could Alan allow anxiety, depression, and fears about cognitive decline and life expectancy to be here now? 

Session 5 practiced defusion – how could Alan change his mind’s attachment to his thoughts?

Session 6 summarised previous sessions and explored the idea of self-as-context – how could Alan remind himself he was more than his own feelings or a diagnosis and create flexibility by changing his habits? 

Before and after therapy, Alan took a series of standardised questionnaires to measure anxiety, depression, defusion, and quality of life. 

What Changed After Therapy?

At the end of therapy, Alan’s depression score dropped from ‘moderate’ to ‘mild’, showing a clinically significative change. His quality of life scores also improved in physical function, general worries, and mood, and he was overall found to be less ‘hooked’ on troubling thoughts (i.e., higher ‘defusion’). On the other hand, Alan’s anxiety remained ‘moderate’, which may be due to his long history of obsessive-compulsive difficulties. Beyond these scores, Alan also mentioned that the sessions were enjoyable and useful, and his caregiver found them helpful in realising she had been neglecting her own self-care and to start finding some time for herself. 

What Does This Mean?

Since this was a single case study without a control group, we need to be careful not to overstate the significance of its results. However, Alan’s decrease in depression, increase in defusion, and improvement in quality of life after only six sessions do suggest that ACT may be a viable and helpful psychotherapy approach for people with HD. Randomised controlled trials (RCTs) are now needed to compare ACT with usual care or other psychotherapies, explore different delivery formats, and monitor efficacy across different HD stages.

TL;DR

• HD is associated with significant psychological challenges that can affect both people with HD and caregivers.
• Psychological care options for HD are scarce, especially due to biomedical perspectives that overlook the burden of adjusting to HD.
• Acceptance and Commitment Therapy (ACT) aims to help people accept difficult thoughts or feelings and unhook from them, stay present, identify values, and take value-guided actions.
• A team at the University of Pennsylvania explored the adoption of an online caregiver-assisted ACT program with a 52-year-old man with HD.
• The results showed improvements in the man’s depression, quality of life, and feeling ‘hooked’ on thoughts; his caregiver found the sessions helpful for her self-care.
• ACT looks promising for people with HD, but evidence is preliminary until more comprehensive trials are carried out.

Learn more

“Acceptance and commitment therapy with Huntington’s disease: A narrative review and case report of a caregiver-assisted intervention“, (open access).

Meet this 2025 HDBuzz Writing Competition Winner

Dr Nicolò Zarotti is an Academic and Clinical Psychologist working in Neuropsychology. He holds a BSc and an MSc in Psychology from the University of Trieste, a PhD in Health Research from Lancaster University, a Doctorate in Clinical Psychology (ClinPsyD) from the University of East Anglia, and a Postgraduate Diploma (PGDip) in Clinical Neuropsychology from the University of Glasgow. He is a Chartered Psychologist (CPsychol) and Associate Fellow (AFBPsS) of the British Psychological Society, an HCPC-registered Practitioner Psychologist, and a Fellow of the Higher Education Academy (FHEA). Dr Zarotti’s main research and clinical work, carried out between the Manchester Centre for Clinical Neurosciences and the University of Leeds, revolves around developing psychological approaches to mental health and cognitive difficulties in people with neurodegenerative conditions such as Huntington’s disease, Parkinson’s disease, motor neurone disease, and multiple sclerosis. 

This year, the HDBuzz Prize is brought to you by the Hereditary Disease Foundation (HDF), who are sponsoring this year’s competition.

We know that HD affects how we move, think, and feel but these symptoms don’t appear overnight. Tiny hidden changes in the brain can begin years before a diagnosis. One way that scientists can detect these early shifts is by measuring brainwaves. This is a painless, non-invasive way to see how the brain is working during rest or while performing simple tasks. 

A recent study used this approach to see whether people who carry the HD gene, both before and after symptoms start, show differences in how their brains respond to unexpected noises. The result of this study suggests that even in the “silent” pre-manifest stage of HD (HD-ISS stage 0), the brain’s automatic reactions are already changing. This could open the door to new ways of tracking HD’s earliest effects. 

Eavesdropping On The Brain’s Electrical Chatter 

You might remember Sherlock Holmes saying, “The world is full of obvious things which nobody by any chance ever observes.”  When it comes to HD, that seems to be especially true. While we often notice the louder, more obvious, symptoms of HD like movement difficulties, mood changes or thinking problems, the brain can “whisper” clues for years beforehand. The challenge for researchers is learning how to listen. 

Our brains are constantly alive with tiny bursts of electricity zipping along and between neurons. Even when we’re resting or not paying attention, this electrical chatter never stops. Imagine a stadium full of fans. From far away, you can’t hear individual conversations, but you can tell when the crowd gasps at a near goal, bursts into cheers, or suddenly falls silent. That’s how brainwaves work, rhythmic electric signals made by networks of brain cells talking to one another.  

To “hear” these brainwaves, researchers use a very fancily named tool called electroencephalography, or EEG, for short. It’s painless, requires no needles, and simply involves placing small sensors on the scalp. EEG doesn’t read our thoughts (sorry, no mind reading here!), but it does detect patterns and timing of brain activity. A bit like noticing when the crowd shifts from calm murmuring to roaring cheers.  

The Brain’s Surprise Detector 

In this study, researchers were particularly interested in a certain brainwave signal called mismatch negativity (MMN). Think of MMN as your brain’s “surprise detector.” Even if you aren’t paying attention, your brain automatically notices when something changes around you. 

Picture yourself on a long train journey, listening to the steady click-clack of the train on the tracks. If one clack sounds different, louder, or higher pitched, your brain reacts instantly, even if you’re daydreaming. That small, automatic reaction is what MMN represents. 

To test this, researchers invited people with the HD gene (both with and without symptoms) as well as volunteers without the gene. While wearing an EEG cap, participants listened to a series of steady beeps, with the occasional odd “bleep” slipped in. EEG measured how strongly and consistently each person’s brain reacted to the odd sounds.  

What the Study Found: Cracking Open The Brain’s Whispering

When the results were compared, one pattern stood out. People with symptoms of HD had smaller MMN signals, especially at the front of the brain. This suggests their automatic “something’s different” response was weaker. 

People who carried the gene but had no symptoms yet did not show a reduction in MMN signal size. But their brainwave timing told an interesting story. The researchers looked at something called theta phase coherence, a fancy way to measure precisely how the brain’s rhythm lined up each time a surprise sound occurred. 

In people without symptoms but who carry the HD gene, their theta phase coherence was higher than in both people with symptoms and those without the HD gene. This is interesting for us as this finding suggests that perhaps the brain is trying to overcompensate, like a drummer keeping an unusually strict beat to hold the rest of the band together. These brainwave changes may be the brain’s way of coping, helping it keep things working in the early stages of the disease.

Why Does This matter?

Think of your brain like an orchestra. In healthy brains, the instruments (neurons) keep perfect time, adjusting smoothly to new notes (unexpected sounds). In early HD, the orchestra might still sound fine to an outside listener, but behind the scenes, the conductor is working overtime to keep everyone in sync, maybe even counting every beat twice. 

This extra timing consistency in people with the HD gene but without symptoms, could be that overworked conductor. The brain finding clever ways to compensate before symptoms emerge. In people with symptoms, that compensation may no longer be enough, leading to weaker responses.

What This Doesn’t Tell Us (Yet)

Like all early-stage research, this study has limits. It involved a relatively small number of participants (25 people with HD symptoms and 14 people carrying the HD gene without symptoms) , so larger studies will be needed to confirm these patterns. In this study, brainwave changes didn’t directly match the results of the other HD symptoms tests the team used, such as thinking, mood or movement assessments typically used in HD research. That doesn’t mean the signals aren’t important, it just means researchers still need to figure out how, or if, these brainwave changes connect to the real challenges people with HD face in their daily lives, like thinking clearly, managing mood, or moving easily.

A Quiet but Promising signal

One of the best parts of this type of research is how easy it is on participants, no tricky tasks, no needles, just sitting back with headphones on while the EEG listens to your brain’s reactions.  In the future, this type of test might even be possible at home.  Because it’s so simple, it could be repeated regularly, making it a valuable way to track changes over time.  A big thank you goes to the amazing participants who made this research possible.

In HD, where the disease can quietly cause damage for years before symptoms appear, that’s a big deal. The sooner we can detect these changes, the earlier we can respond. For now, this research is a promising step, not a finished tool. But it shows that the brain’s whispers are there if we know how to listen. And just like Sherlock Holme said, the clues are often in plain sight, or in this case, plain sound, waiting for someone to observe them. 

Summary

• Brainwave changes can appear in people with the HD gene before symptoms show.
• EEG detects the brain’s automatic “surprise responses” in a painless, simple test.
• Early-stage gene carriers show compensating brain activity, while symptomatic HD shows weaker signals.
• EEG could become a home-friendly tool to track HD long before obvious symptoms appear.

Learn More 

To find out more please see the original research article, “Auditory mismatch negativity in pre-manifest and manifest Huntington’s disease” (open access).

Meet the 2025 HDBuzz Writing Competition Winner

Eva Woods is a PhD student at Trinity College Dublin, Ireland. Eva completed her BSc in Biological and Biomedical Sciences at Maynooth University, where she worked with the Department of Electronic Engineering on a final-year project investigating EEG-based Brain-Computer Interfaces. Following this, she progressed directly into her PhD at Trinity. A key focus of Eva’s research is identifying early changes in the brain in people who carry the Huntington’s disease gene but have not yet shown symptoms. Her work combines brain imaging (MRI) with techniques such as electroencephalography (EEG), which records tiny electrical signals from the brain, and transcranial magnetic stimulation (TMS), which uses magnetic pulses to safely stimulate brain activity. Through this research, she aims to improve understanding of early disease mechanisms and contribute to the search for new biomarkers of disease progression. Eva is also passionate about science literacy and engaging Huntington’s disease families in Ireland with research. Each year, she hosts “TCD’s Huntington’s Disease Research Day”, which brings together researchers, clinicians, advocates, and families from across the country. The event is designed to be welcoming and accessible, with talks delivered in clear, easy-to-understand language and plenty of space for families to ask questions and engage with speakers in a supportive environment.

This year, the HDBuzz Prize is brought to you by the Hereditary Disease Foundation (HDF), who are sponsoring this year’s competition.

This Fall, HDBuzz is proud to launch our “Falling Into Hope” fundraising campaign. Our goal is simple but ambitious: raise $30,000 in the next 8 weeks, by October 28.

2025 will be a landmark year in HD research. We’re closer than ever to disease-modifying therapies, and clear, unbiased reporting has never been more essential.

Why Independence Matters

We’re thrilled to share that HDBuzz is now an independent 501(c)(3) non-profit organization in the US! This milestone marks our transition out of the fiscal sponsorship of the Hereditary Disease Foundation, who generously supported us for the past year. We’re deeply grateful for their role in helping us get here.

Now, as we step fully into independence, we need your support to keep HDBuzz strong and sustainable. Unlike many organizations in the HD landscape, we make a deliberate choice not to accept funding from pharmaceutical companies. That independence means you can trust us to remain unbiased, especially as we get closer to having disease-modifying drugs.

2025 will be a landmark year in HD research. We’re closer than ever to disease-modifying therapies, and clear, unbiased reporting has never been more essential.

What Your Donations Support

Every dollar raised through Falling Into Hope directly supports:

• Transitioning to independence as a stand-alone non-profit
• Maintaining unbiased reporting on HD science and clinical trials
• Expanding global access, including automated translations into 10 languages by the end of the year
• Training the next generation through the HDBuzz Prize writing competition
• Reaching more families with the help of our new social media manager and updated website

Your donations don’t just keep the lights on. They ensure that HD families everywhere can rely on accurate, accessible science communication at this critical moment in history.

A Trusted Global Resource

This year, we’ve built capacity in big ways: a new advisory board of leaders in HD research (Dr. Hugh Rickards, Dr. Vanessa Wheeler, Dr. Ray Truant, Dr. A. Jenny Morton), a WordPress upgrade behind the scenes, and expanded outreach through social media.

We’re also proud to showcase the 2025 HDBuzz Prize winners, early-career scientists who will publish their articles this month! Their work is a glimpse of the future — not just of HD science, but of science communication.

Unlike many organizations in the HD landscape, we make a deliberate choice not to accept funding from pharmaceutical companies. That independence means you can trust us to remain unbiased, especially as we get closer to having disease-modifying drugs.

Join Us: Fall Into Hope

The next 8 weeks will determine how boldly HDBuzz can grow in 2025 and beyond. Our mission is clear. We want to keep science communication accessible, unbiased, and global, no matter what breakthroughs come next.

But we can’t do it without you. Help us raise $30,000 by October 28. Your gift makes the difference between simply reporting on progress and ensuring every HD family, everywhere, has the knowledge they need to face the future with the knowledge they’ll need as we advance toward disease-modifying therapies.

Donate now

Summary

• HDBuzz has launched “Falling Into Hope”, an 8 week campaign to raise $30,000 by Oct 28.
• Donations support our transition to independence and our mission to stay unbiased.
• We never take pharma money. Our independence ensures trust, especially as we approach the era of disease-modifying drugs.
• Funds fuel translations into 10 languages, social media outreach, and the future HDBuzz Prize writing competitions.
• Your donation today keeps HD families everywhere informed with clear, unbiased science at this historic moment.

This month’s Huntington’s disease (HD) research roundup spans work from the dinner table to DNA repair. Scientists explored whether eating on a schedule could help clear toxic proteins, uncovered early signs of muscle loss in HD, and examined how childhood experiences shape adult mental health. Other teams investigated the gut–brain connection, identified new protein biomarkers, mapped toxic huntingtin clumps, and revealed how tiny changes in DNA repair genes might speed up disease onset. Together, these discoveries highlight both the complexity of HD and the many creative ways researchers are working to tackle it.

Appetite for Answers: Does Eating on a Schedule Help with Huntington’s Disease?

This month we covered work from researchers who are eyeing whether when (rather than what) you eat could benefit people with HD. Known as time‑restricted eating (TRE), the idea is to limit meals to a daily window, like 12 p.m. to 8 p.m., and let the body fast the rest of the time. In animals that model HD, this eating pattern appears to kick-start a cleanup process inside cells (called autophagy) that may help clear out harmful huntingtin protein clumps from the brain.

But before giving your fridge a curfew, remember this: these promising results are from animal studies, not people. And many folks with HD already struggle with unintended weight loss, problems with choking, and muscle wasting, so fasting could unintentionally make symptoms of the disease worse. So even though more research is needed before TRE is prescribed for HD, we know that a healthy diet filled with nutritious food has clear health benefits for everyone.

Body in Decline: Muscle Loss as an Early Symptom of Huntington’s Disease

A new study shows that HD doesn’t just impact the brain, it quietly reshapes the body too. In the earliest stages, people with HD already appear to have signs of reduced muscle mass (60%) and weaker grip strength (45%), even when walking still felt normal. On top of that, over half (55%) seemed to be at risk for or already experiencing malnutrition, a worrying early red flag.

These early physical declines aren’t just numbers, they’re affecting daily life. Reduced strength and nutrition were linked to worse motor symptoms, increased dependence on others, and trouble planning or organizing tasks. The good news is that there’s hope with practical solutions that can be implemented today. Nutritional support, high-calorie or easy-to-eat meals, and staying active with exercises like walking or resistance training could help towards preserving muscle, brain health, and independence. Looking ahead, measuring changes in body composition may one day offer a simple, non-invasive way to monitor disease progression.

Carried from Childhood: Childhood Experiences and Adult Mental Health in Families with Huntington’s Disease

Some childhood memories stick with us in surprising ways, even long into adulthood. A study from Italy looked at adults who grew up with a parent affected by HD and discovered that it wasn’t major crises, but ongoing emotional turbulence, like constant criticism, unpredictable moods, or feeling unsafe speaking up, that had the strongest impact on adult mental health.

Those who grew up in HD families were more likely to struggle with low mood, anxiety, and feeling overwhelmed, even when major traumatic events hadn’t happened. The research helps name what many people have quietly carried for years and why emotional support matters just as much as practical help. Most importantly, it reminds us that healing is possible, and you don’t have to carry it alone. 

If you would like to learn more about support systems and resources available for young people impacted by HD, we encourage you to reach out to the Huntington’s Disease Youth Organization (HDYO) or the Huntington’s Disease Society of America (HDSA) National Youth Alliance (NYA). You are not alone, and support is available. 

The Gut–Brain Superhighway in Huntington’s Disease: Clues From the Microbes Inside Us

Our gut and brain are always chatting – think of it like a busy two-way highway where nerves, immune signals, and gut microbes all send messages back and forth. In HD, this roadway gets bumpy: gut and brain barriers become leaky, inflammation kicks in, and the usual balance of gut microbes gets thrown off, like traffic patterns suddenly going haywire.

Researchers are looking into how we might ease the congestion. Lifestyle factors like exercise or a stimulating environment have helped gut health in animal models, and certain antibiotics showed less inflammation and better nerve cell protection in lab studies. While broad spectrum antibiotics aren’t a realistic option for intervening with the HD microbiome long term, these studies help identify molecular players that could be targeted with new medicines down the road to improve gut and, potentially, brain health in HD. 

City Under the Microscope: How Two Proteins Could Help Track Huntington’s Disease

Scientists are on the hunt for better ways to measure HD progression, even before symptoms show. In recent work, two proteins, CAP1 and CAPZB, identified using a blood test, have become lead candidates . In a study from Cyprus, researchers scanned the entire blood protein landscape and discovered that CAP1 levels dip in people in the very earliest stage of HD, while CAPZB levels rise consistently throughout the disease.

This month’s Huntington’s disease (HD) research roundup spans work from the dinner table to DNA repair. Together, these discoveries highlight both the complexity of HD and the many creative ways researchers are working to tackle it.

This is important research because we need more biomarkers that track with HD progression. Right now, neurofilament light (NfL), the leading HD biomarker, only tells part of the story. But having others like CAP1 and CAPZB joining the team would give researchers more ways to track disease progress and test treatments earlier and more accurately. If future studies in larger, more diverse groups confirm these findings, one day a simple blood test could reveal whether a new treatment is slowing HD before noticeable symptoms take hold, an exciting possibility for an early intervention.

Cracking the Protein Puzzle in HD: New Blueprints Offer Hope for Stopping Damage Early

Researchers have advanced what we know by mapping the structure of the huntingtin protein fragments, piece by piece, using ultra-precise imaging. Sticky protein clumps, called exon 1 fibrils, are the misfolded proteins that accumulate in HD and participate in the havoc that is wreaked in brain cells. Scientists discovered that these toxic clumps have a tight, dense core wrapped in a loose, fuzzy coat. With this new work, we can see exactly how each part fits together.

In a clever follow-up, researchers added a tiny amount of curcumin, the active ingredient in turmeric, to the mix in lab dishes. This gentle tweak seemed to reshape the protein clumps into forms that were slower to assemble, less sticky, and less harmful to neurons. The studies offer a new kind of blueprint as a way not just to clean up damage after it happens, but potentially to build safer versions from the start. 

But don’t start downing massive amounts of curcumin or turmeric with the hopes of altering the expanded huntingtin structure. These findings are early-stage and in a lab setting only and more work is needed to better understand the effects in people. However, they give scientists an exciting map to start designing treatments that target the blueprint of the huntingtin protein.

When DNA Repair Goes Off-Script: How a Small Change in FAN1 Can Accelerate Huntington’s Disease

Deep inside our cells, proteins work like stagehands keeping DNA maintenance running smoothly. But researchers have spotlighted a tiny change, called the R507H mutation, in one of the DNA repair proteins, FAN1, that causes it to trip up its performance. This small slip weakens FAN1’s grip on PCNA, a partner protein that helps it stay on track during DNA repair, ultimately letting harmful DNA loops accumulate in the huntingtin gene, seemingly speeding up disease onset.

This work is important because it helps explain why two people with identical CAG repeat numbers within their huntingtin gene might start showing symptoms at very different times. Understanding the R507H change in FAN1 gives researchers a new target. If they can restore FAN1’s grip or stabilize its teamwork with PCNA, they may be able to slow the progression of HD. This opens up a fresh strategy in the hunt for therapies by targeting genes that modify the onset of HD.

Two research teams have uncovered how a small change in FAN1, a DNA repair protein, can speed up Huntington’s disease (HD). In back-to-back papers in Nature Communications, they show how a single mutation known to influence when symptoms begin appears to prevent FAN1 from working properly. This seems to make it harder for cells to keep harmful DNA changes in check. Let’s look at what they found.

DNA Repair and Repeat Expansions in HD

Keeping our genetic material in check is a constant job for the cells of our body. Our DNA is under constant stress from all kinds of damage, ranging from UV damage caused by the sun to correcting molecular errors to ensure new mutations aren’t made, and cells rely on a network of repair proteins to fix problems before they cause harm.

The role of these DNA repair players has been shown to be important in HD. In particular, many different teams of researchers have shown that the C-A-G DNA letter repeat region of the HTT gene can get longer and longer over time in some types of cells. This so-called somatic instability, or somatic expansion, is thought to play a central role in how early and how severely the disease appears.

FAN1 is one of several proteins that help manage these repetitive DNA sequences, typically preventing them from expanding over time. Another key player in this repair process is PCNA, a protein that acts like a supporting actor, helping the leading players, including proteins like FAN1, stay on script during DNA repair.

The R507H Mutation in FAN1

Generally, the longer the CAG number someone has, the earlier they will begin to experience symptoms of HD. However, we also know that for two people with the exact same CAG number, their symptoms may begin decades apart. This is in part due to things called genetic modifiers: other DNA changes in the genome, aside from the HD mutation, which are associated with differences in when symptoms begin.

Some people with HD carry a specific change in the FAN1 protein, known as the R507H mutation. While this might seem like a confusing code, the letters and numbers let researchers know precisely where and what the change is, like the page and line numbers in a script – at the 507th spot within FAN1, an “R” protein building block is swapped for an “H”.

This single-letter change alters just one building block in a protein of more than 1,000 building block letters, or amino acids. Although it’s a small change, people carrying this FAN1 variant tend to develop symptoms much earlier than expected based solely on their CAG number. Until now, the reason behind this link wasn’t well understood.

Using powerful microscopes, researchers were able to visualize how FAN1 normally binds to PCNA. This binding allows FAN1 to position itself properly onto DNA to carry out its repair work. But the R507H mutation weakens this interaction, reducing FAN1’s ability to hold on to PCNA and stay in place during repair.

A Closer Look at the Consequences

Both studies examined the effects of the R507H mutation in detail. One found that FAN1’s ability to cut the loops that form in CAG repeats in DNA seemed to be reduced. The other suggested that the entire FAN1–PCNA–DNA complex was less stable and less effective at DNA repair when the R507H mutation was present.

These DNA loops are also called extrusions, as they stick out awkwardly from the DNA helix, like a stage prop out of place. These extrusions tend to form in regions with many repeats, like the CAG tract in the huntingtin gene. The longer they are, the more unwieldy they become. If not properly repaired, they can lead to further expansions, making HD symptoms worse over time.

Why This Matters

These findings offer an explanation as to why the R507H mutation might be linked to earlier HD onset: the mutation disrupts FAN1’s repair activity, which can lead to faster accumulation of harmful DNA changes, and more somatic expansion. Overall, this could explain why this genetic modifier hastens the onset of HD symptoms.

These detailed insights into how FAN1 can go off script in some people with HD not only deepen our understanding of the disease, but also open up new directions for treatment. By mapping out the exact role of FAN1 in HD pathology, researchers can begin to explore ways to restore proper repair function, for example, by designing therapeutics that stabilize the FAN1–PCNA interaction or by boosting FAN1 levels.

And there are companies already doing exactly that! For example, Harness Therapeutics is working on developing specialized DNA molecules, known as antisense oligonucleotides or ASOs, that are designed to boost production of FAN1, with the overall aim of making the C-A-G repeat shorter.

While much of HD therapeutic research has focused on lowering levels of the harmful huntingtin protein, these results suggest that strengthening the cell’s natural DNA repair processes could offer another way to slow disease progression. Perhaps this could one day be applied together with huntingtin lowering. The more approaches we explore, the greater the chances of finding an effective therapy for HD.

Finally, recognizing this mutation in people with HD may help tailor care strategies in the future, pointing toward a time when therapies are prescribed based on each person’s genetic makeup.

Moving Forward

Thanks to these two new studies, we now have a clearer picture of how a small change in FAN1 can tip the balance, accelerating the progression of HD. This insight was only possible because of the generosity of HD families around the world who contributed samples to the large genetic studies that first identified this variant.

With more research, we may one day be able to correct or compensate for that shift, helping people with HD live healthier, longer lives.

Summary

• FAN1 is one of several DNA repair proteins that help keep repetitive DNA sequences in check.
• A specific change in FAN1, called R507H, seems to reduce its ability to interact with PCNA, another key repair protein.
• This disruption appears to make it harder for cells to manage CAG repeats in the huntingtin gene, potentially accelerating HD onset.
• Understanding this process opens the door to new therapeutic strategies, such as stabilizing DNA repair pathways.
• These insights were made possible thanks to HD families worldwide, whose contributions to genetic studies enabled the discovery of this mutation.

Learn more:

“A FAN1 point mutation associated with accelerated Huntington’s disease progression alters its PCNA-mediated assembly on DNA” (open access).

“Structural and molecular basis of PCNA-activated FAN1 nuclease function in DNA repair” (open access).