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Huntington Hunting: Diagnosis in 5 minutes

January 14, 2019

Huntington's Disease and some other diseases of the brain are caused by excess DNA sequences. Swiss researchers have developed a method that can be used to determine the length of mutated genes in just over ninety minutes.

People suffering from Huntington's illness suffer from uncontrolled body movements and a decrease in their mental abilities. As a rule, the disease leads to the death of patients approximately 15-20 years after the diagnosis. This is due to the fact that the site of the HD gene is longer than that of healthy patients. The mutant gene causes the death of brain cells.

5 hours will be 5 minutes

The length of the mutant gene segment today is labor-intensive determined in more than one hourly laboratory analysis. The team headed by professor of SNSF professor at the University of Lausanne, Vincent Dion, has now collaborated with the Toulouse staff to develop a reliable method for measuring the long segment of the DNA responsible for the disease. The measurement result is available in only ninety minutes. Thus, the entire diagnosis can be done more than three times faster than before.

The DNA to be analyzed is extracted from blood cells. The research team expands the sequence of affected genes and defines its length with the help of a newly formed chip. It has two small funnel-shaped chambers that only have a portion of a millimeter wide. Under voltage and high pressure molecules of electrically charged DNA can be separated by their length. Shorter sequences move deeper into the funnel than longer ones. The length of the fluorescent marker is easy to read under a microscope.

Uneven lengths are the result of a different number of repetitions of the letters (nucleotides) of the genetic code (CAG) – a typical feature of trinucleotide diseases such as Huntington's disease. A mutation causes a devastating change in coded protein. Their cause is not fully understood, but the newly formed protein is toxic to brain cells. Despite the fact that DNA has a maximum of 35 repetitions in healthy people, patients with HD have 40 or more. Knowing the exact length of the affected sequences is important for the prognosis and therapy of this incurable disease. "Our process is thinner and faster than the currently used methods," says Dion.

As part of the project, the team worked with a group around Aurélien Bancaud from the Laboratory of Analysis and System Architecture (LAAS) in Toulouse, which developed and patented a new method. Picometrics Technologies has been licensed to produce a product called μLAS.

Just cut out the bad places

Huntington's Disease is just one of more than twenty known trinucleotide diseases. These include spinocerebellar ataxia, brittle syndrome X, myotonic dystrophy and Friedrich ataxia. There is currently no treatment for these hereditary diseases, but there may be hope: Dion has recently developed a method that uses the CRISPR / Cas method to cut mutated sequences. "However, there is still a long way from demonstrating the effectiveness of cell cultures to potential use in medicine," says Dion.

This press release is based on a press release from the Swiss National Science Foundation (SNSF).

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