Only a few decades ago, people suffering from genetic disorders were left to wonder what was causing their health problems. It may have taken years or even decades of testing and waiting before receiving a diagnosis, which didn't always reveal much about their condition. But things are changing dramatically, as the cost of genomic sequencing has dropped dramatically, and the computational tools used to analyze genetic data continues to become more sophisticated.
Scientists have identified the genetic mutations that cause many different genetic disorders, some which only affect a handful of people. Researchers are also finding new ways to identify genetic disorders more quickly, and develop methods that don't require the entire genome to be sequenced.
An international team of researchers have now created a single test that can screen for 50 different diseases including several types of muscular dystrophy, Huntington’s disease, and fragile X syndrome. Many of these diseases have not been easy to diagnose with standard methods. The new test has been reported in Science Advances, and validation studies that will bring it to the clinic are now underway. This technology might be used routinely in clinics within five years.
This test uses the DNA in a blood sample, and relies on nanopore sequencing technology, which uses a very small and inexpensive machine. The test focuses on diseases that are caused by errors in genetic features known as short tandem repeats (STRs). In some people, the STR sequences in certain genes are too long, leading to a class of diseases called Short Tandem Repeat (STR) expansion disorders.
The Nanopore device was reprogrammed to zero in on about 40 genes that have been already been shown to cause STR expansion disorders. Abnormally long repeats are identified by the test. Current genetic sequencing technologies sometimes have difficulty deciphering long, repetitive sequences and the diseases present complex symptoms, making the disorders difficult to diagnose, said senior study author Dr. Ira Deveson, Head of Genomics Technologies at the Garvan Institute.
"In the one test, we can search for every known disease-causing repeat expansion sequence, and potentially discover novel sequences likely to be involved in diseases that have not yet been described," said Deveson.
"We correctly diagnosed all patients with conditions that were already known, including Huntington’s disease, fragile X syndrome, hereditary cerebellar ataxias, myotonic dystrophies, myoclonic epilepsies, motor neuron disease and more,’ said Deveson.
Treatments for repeat expansion disorders are limited, but if patients receive a correct diagnosis sooner, they are not only saved what could be a long, stressful journey to solve their mystery, they might be able to get therapeutics that prevent more complications from developing.
Sources: Garvan Institute, Science Advances
