Through a collaboration with graduate and undergraduate students, MDF's Chief Scientific Officer, Dr. Andy Rohrwasser, aims to share groundbreaking scientific discoveries with lay audiences. This article was reviewed and summarized by Asmer Aliyeva, PhD Candidate in Dr. Andy Berglund’s lab at the RNA Institute, Department of Biological Sciences at the University at Albany, SUNY, NY.

Some diseases that affect the brain, muscles, and nerves are caused by tiny pieces of DNA that repeat too many times. These repeated sections can cause serious problems when they get too long. Diseases like Huntington’s, Friedreich’s ataxia, and myotonic dystrophy are caused this way.

• Huntington’s happens when there are too many CAG repeats in the HTT gene.
• Friedreich’s ataxia is caused by too many GAA repeats in the FXN gene.
• Myotonic dystrophy type 1 (DM1) is caused by too many CTG repeats in the DMPK gene.
• Myotonic dystrophy type 2 (DM2) is caused by too many CCTG repeats in the CNBP gene.

As repeats grow longer over time or through generations, they make the disease worse.

A New Way to Help: Base Editing

Scientists found that breaking up these long repeats with different DNA letters can make the disease start later or be less severe. A research team at Harvard tested if they could do this using a tool called base editing. Think of DNA like a book written with the letters A, T, C, and G. Base editing works like an eraser-pencil combination that can fix one wrong letter without tearing the entire page or making the sentence unreadable. The editing tool finds the right letter and carefully changes it.

The scientists used this method on cells and mice with Huntington’s and Friedreich’s ataxia. It stopped the repeats from growing and sometimes even made them shorter. In mice, it even helped reduce repeat growth in the brain. But sometimes the tool changes the wrong part of DNA, so scientists are working to make this eraser-pencil tool safer.

What About Myotonic Dystrophy?

Myotonic Dystrophy (DM) is caused by extra repeats—CTG for DM1 and CCTG for DM2. It can cause muscle weakness, trouble relaxing muscles, heart issues, and more. Like the other diseases, the more repeats there are, the worse it gets. This study gives hope that base editing might help people with DM, too. If it works safely, it could slow down the disease, reduce symptoms, and lead to better treatments in the future.

Why It Matters

Base editing is a new and precise way to fix small DNA mistakes. It’s still being tested, but it could bring better treatments for diseases like Huntington’s, Friedreich’s ataxia, and Myotonic Dystrophy. Click here to learn more about base editing!

Original Publication: 

Matuszek, Z., Arbab, M., Kesavan, M. et al. Base editing of trinucleotide repeats that cause Huntington’s disease and Friedreich’s ataxia reduces somatic repeat expansions in patient cells and in mice. Nat Genet (2025). https://doi.org/10.1038/s41588-025-02172-8