As reported on MedicalXpress, a newly developed RNA-focused analytical method may improve the detection and characterization of repeat expansion disorders, a group of genetic conditions that includes Huntington’s disease, amyotrophic lateral sclerosis (ALS), and certain muscular dystrophies. The approach, described by researchers at the University of Cambridge and collaborators, uses engineered RNA structures and nanopore sensing to more precisely measure disease-associated genetic repeats.
Addressing a Major Diagnostic Gap
Repeat expansion disorders occur when short, repetitive DNA sequences grow beyond normal lengths, disrupting cellular processes. These conditions collectively affect an estimated 1 in 280 individuals, yet the majority of cases remain undiagnosed, underscoring the need for reliable and scalable testing solutions.
Accurate measurement of repeat size is clinically important because disease onset, severity, and inheritance risk are often closely tied to the length of these expansions. Even relatively small differences can have significant consequences. For example, incremental increases in repeat numbers in certain genes can shift disease presentation from mild to severe or determine whether symptoms appear at all.
However, measuring repeat expansions remains technically challenging. Standard polymerase chain reaction (PCR) approaches can introduce biases that distort repeat length, and some sequencing technologies struggle to accurately read long, repetitive regions.
Moving Beyond DNA-Centric Methods
The Cambridge team sought to overcome these limitations by focusing directly on RNA, which carries functional information reflecting disease states but is typically harder to analyze due to its instability.
The new method uses short DNA strands to fold RNA molecules into defined “origami-like” nanostructures. These engineered RNA constructs are then passed through nanopores, nanoscale holes that detect molecules via changes in electrical current. As each structure travels through a pore, it generates a signal pattern that corresponds to its shape and, critically, the number of repeated sequences it contains.
This approach enables measurement at a resolution of approximately 18 nucleotides, sufficient to distinguish between normal and disease-associated repeat lengths.
Sensitivity and Minimal Sample Requirements
A notable advantage of the technique is its ability to operate using very small amounts of RNA, an important consideration in clinical settings where sample availability may be limited. This sensitivity could make the method particularly useful for early-stage diagnostics or rare sample types.
By preserving RNA-specific information that may be lost in DNA-based assays, the technique also provides a more direct view of molecular disruptions associated with disease.
Potential Clinical Applications
While still in early-stage development, the method could complement existing diagnostic workflows rather than replace them outright. In particular, it may be useful for:
- Targeted testing in patients with known familial risk of repeat expansion disorders
- Refinement of repeat sizing when conventional methods yield ambiguous results
- Monitoring therapeutic response, especially as disease-modifying treatments become available
The researchers note that repeat length can change over time or vary between tissues, making dynamic measurement tools potentially valuable for ongoing disease management.
Steps Toward Clinical Translation
Despite promising laboratory results, several hurdles remain before the technology can be widely adopted. The system has not yet been validated using patient samples, and scaling the platform for high-throughput clinical use will require parallelization of nanopore sensors to ensure timely results.
Efforts to translate the platform into a diagnostic tool are underway through Cambridge Nucleomics, a university spin-out company. Future work will focus on demonstrating reliability in real-world clinical material and optimizing the system for routine use.
Outlook
As precision medicine advances, accurate and efficient measurement of genetic repeat expansions is likely to play an increasingly important role in both diagnosis and treatment monitoring. The RNA origami nanopore approach represents an innovative step toward addressing this need, offering a potentially faster and more precise alternative to existing techniques.
If validated in clinical settings, it could help close the diagnostic gap for repeat expansion disorders and improve outcomes through earlier and more tailored interventions.
