DNA Sequencing Reduces Huntington's Disease Diagnosis

Huntington's disease is an inherited neuro-degenerative disorder, which stops parts of the brain working properly, with symptoms worsening over time, and is usually fatal within 20 years. Currently individuals with symptoms of Huntington's disease have a blood test and can wait up to four weeks for the result.

Huntington disease is caused by mutations in the HTT gene, which provides instructions for the production of a protein called huntingtin. The function of this protein is still unknown but it appears to play an important role in the neurons of the brain. The HTT mutation involves a region of DNA that consists of repeated cytosine, adenine, and guanine (CAG) nucleotides. This is known as a trinucleotide repeat. Normally, the CAG trinucleotide is repeated 6 to 35 times within the gene. However, in people with Huntington disease, the CAG segment is repeated more than 35 times.

The world's first genetic test for Huntington's disease using nanopore-based DNA sequencing technology is now available at Guy's and St Thomas' NHS Foundation Trust (London, UK). Viapath has recently introduced Oxford Nanopore long read sequencing technology into its Genetics Laboratory. This technology allows them to rapidly sequence long stretches of DNA using a small palm-sized device. Unlike short read ‘next generation’ sequencing; long read sequencing provides the ability to sequence the entire HTT CAG repeat region in a single read.

The scientists used the MinION, which is a small hand-held device that "decodes" individual strands of DNA in real-time. It identifies any changes in the DNA sequence and then matches these to a library of known genetic sequences to detect presence of the genetic disorder. Most current technologies provide segments of DNA sequence that need to be analyzed at a later date, which leads to a longer wait for results.

Jonathan Edgeworth, MB BCHir, PhD, MRCP, FRCPath, a professor and Viapath’s Medical Director, said, “This advance was made possible through a research partnership involving front-line clinicians, academics and healthcare scientists. Everyone came together with a single vision to speed up the pathway moving scientific discovery and technological advance to the bedside. This approach will be of immense benefit to patients. We are evaluating whether this technology can speed up diagnosis of a range of diseases including infections and cancers, to more rapidly identify best treatments based on individual DNA profiles.”

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Guy's and St Thomas' NHS Foundation Trust