A Surprising Genetic Link Between Myotonic Dystrophy and Autism
New research is shedding light on how a rare neuromuscular condition may help us better understand autism spectrum disorder (ASD). Scientists have found that tandem repeat expansions—a type of DNA mutation—could play a major role in autism risk, especially in individuals with a condition called myotonic dystrophy type 1 (DM1).
DM1 is an inherited disorder that causes muscle weakness, but now researchers believe its underlying genetic mechanism may also impact brain development. The discovery could open the door to new therapies that target autism at the molecular level.
What Are Tandem Repeat Expansions?
Tandem repeat expansions (TREs) happen when small segments of DNA repeat more times than normal. While repeats are common in the human genome, certain patterns can become toxic when they grow too large. In the case of DM1, a gene known as DMPK contains these repeat sequences. As they expand, they produce a mutated form of RNA that behaves like a sponge—absorbing proteins that the brain needs to develop properly.
This process throws off a crucial step called gene splicing, which helps cells decide which version of a protein to make. Without proper splicing, brain-related genes don’t function as they should, potentially leading to ASD-like behaviors.
How Tandem Repeat Expansions and Autism Are Connected
Research teams at The Hospital for Sick Children (SickKids), University of Las Vegas Nevada, and other institutions discovered that individuals with DM1 are 14 times more likely to develop autism than the general population. By studying how the toxic RNA from the DMPK gene interferes with gene splicing, scientists found that the same proteins affected in DM1 are also important in autism-related genes.
These proteins, especially one called MBNL, help regulate how RNA is processed in the brain. When MBNL is absorbed by the toxic RNA, it can't do its job. This results in “mis-splicing” of key autism-related genes, disrupting how the brain forms connections during development.
In mouse models, these changes also led to behaviors commonly associated with autism, such as differences in social interaction and sensitivity to new environments.
Exploring Therapies to Reverse the Damage
While this research is still in early stages, it points toward a future where therapies could focus on releasing the trapped proteins and restoring normal brain function. One scientist involved in the study had previously found a molecule that shrinks harmful TREs in other conditions, such as Huntington’s disease. If similar strategies can work for DM1, they may one day help treat autism symptoms that stem from genetic mis-splicing.
Why This Matters for the Future of Autism Care
For years, autism research has focused on gene deletions or mutations that turn gene activity off. This study introduces a new perspective: that autism traits can also result from an overload—too much of something toxic clogging the system, rather than something missing.
Understanding how tandem repeat expansions and autism are linked helps shift the way researchers and clinicians look at both diagnosis and treatment. It opens the door to precision medicine tailored not just to the condition, but to the underlying genetic mechanisms that cause it.
References
Yuen, R. K., et al. (2024). Autism-related traits in myotonic dystrophy type 1 model mice are due to MBNL sequestration and RNA mis-splicing of autism-risk genes. Nature Neuroscience. https://doi.org/10.1038/s41593-024-01781-z
Neuroscience News. (2024). Tandem repeat expansions may explain autism risk. https://neurosciencenews.com/autism-dm1-genetics-25502/
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