Base Editing Strategy Rewrites Huntington's Gene to Reduce Toxic Fragments Without Silencing Protein Function
Key Insights
University of Illinois researchers developed a base-editing tool that alters the HTT gene (search) so cells skip over a region prone to generating toxic protein fragments, rather than turning the gene off entirely.
In mouse models, the treatment reduced toxic protein accumulation, alleviated disease symptoms, and decreased brain degeneration compared to untreated mice.
The team screened over 140 base editors to identify candidates with high efficacy and minimal off-target effects before delivering them into the brains of mice with mutant HTT genes.
A gene editing strategy that rewrites—rather than silences—the gene responsible for Huntington's disease (search) has demonstrated the ability to reduce toxic protein fragments and alleviate disease symptoms in mice, according to researchers at the University of Illinois Urbana-Champaign (search).
The approach, developed by bioengineering professors Pablo Perez-Pinera and Thomas Gaj, uses base editing technology to introduce a precise chemical change at a specific point in the huntingtin (HTT) gene. This edit causes the cell's protein-making machinery to skip over a small section of the gene that is prone to generating toxic fragments, while preserving enough huntingtin protein (search) to carry out its normal functions.
"Our results suggest a new way of thinking about treating Huntington's disease (search): Instead of inactivating the protein completely or targeting collateral pathways, we introduce a very small edit in the gene that changes how the protein is processed by the cells," said Perez-Pinera. "For Huntington's disease, this is an exciting development because there is no cure and having multiple possible treatments in the pipeline provides a reason for hope."
A Different Approach to Gene-Based Therapy
Huntington's disease (search) is an inherited neurodegenerative condition caused by a mutation in the HTT gene (search) that makes the huntingtin protein (search) susceptible to cleavage into toxic fragments. These fragments progressively destroy brain cells, leading to loss of motor control and cognitive decline. Because symptoms typically emerge in middle age, individuals may unknowingly pass the condition to their children before receiving a diagnosis.
While other gene-based treatments have pursued strategies that turn the HTT gene (search) off entirely, the Illinois team sought to preserve the protein's beneficial functions. "Our base editors were developed to target the region of HTT that, when cleaved, can initiate the chain of events that leads to the toxic fragments," Gaj explained. "The result is that instead of turning the protein off completely, we alter how the gene is read so that the most damaging protein fragments are not produced."
Screening and Preclinical Results
The research team screened more than 140 base editors—a gene editing technology that chemically converts one DNA base to another without cutting both strands of DNA—to identify candidates with the highest efficacy and fewest unintended effects. The most promising editors were then injected directly into the brains of mice carrying mutant HTT genes.
Mice that received the base-editing treatment showed reduced accumulation of toxic protein fragments, diminished disease symptoms, and less neurodegeneration compared to untreated animals.
"This approach not only shows that base editors have the potential to be used for Huntington's disease (search), it also opens the door to a new kind of potential treatment for other genetic conditions," Gaj said. "This study helps to show that treating genetic diseases can be done without inactivating a gene or directly correcting a mutation. Sometimes, it is possible to implement modifications to change how proteins function and that could be sufficient to protect the body from further damage."
Next Steps and Delivery Challenges
The researchers are now focused on refining the delivery of base editors to the brain, with the goal of developing methods that are less invasive and do not depend on viral vectors for transport, according to Illinois graduate student Kyrollos Shenouda. "We're also interested in adapting this approach to target other regions of the HTT gene (search) to decrease other toxic aspects of the protein," Shenouda added.
The findings represent a conceptual shift in how gene editing might be applied to Huntington's disease (search) and potentially other genetic conditions, where subtle modifications to protein processing—rather than complete gene inactivation—could yield therapeutic benefit.