In a laboratory at the Hospital for Sick Children in Toronto, scientists embarked on a DNA hunt for around 10.000 families, many of whom have children with autism. Through this research they have identified something they call "genetic wrinkles" in DNA itself: a breakthrough which they believe may explain why some individuals are on the autistic spectrum.
The hope is that this could be an important new clue in autism research. It could allow you to diagnose autism spectrum disorder early or even treat it. Dr Stephen Scherer, co-author of the study and director of the Center for Applied Genomics at SickKids, told CTV News that the new discovery is "truly exciting". "Research on tandem repeats, these particular wrinkles in DNA, reveals a whole new class of genes that we didn't previously know were involved in autism," he said.
We know they are involved in brain function but we don't know how they fit the puzzle
Stephen Scherer
New challenge, new goal
Current research estimates that genetic factors should be found in 50 to 90% of people with autism spectrum disorders. Scientists already know about 100 genes that play a role in the development of autism, but these genes explain only less than 20% of cases.
To further investigate these genetic components, the researchers had to "develop new methodologies," said Scherer. Ryan Yuen, the foreman of this new study, took up the challenge. Nine years ago, he developed a "new computational approach" that allowed him to search for specific features within the DNA itself and to compare the patterns found in individuals with autism with their parents or "other controls in the population".
Now they have found that parental DNA sections are sometimes doubled - or, in some cases, tripled - in their children. A phenomenon called "tandem repetition" (that's what it is). "Tandem repeats are nucleotides, the building blocks of DNA, repeated next to two or more times." "They are like DNA wrinkles."
When these "wrinkled" strands of DNA are replicated, the repetition may stretch, which is why a tandem repetition present in a parent's DNA could expand from parent to child. The larger these wrinkles, the more likely they are to interfere with gene function, also contributing to autism spectrum disorder.
Autism spectrum disorder, today it is less complicated to look for its causes
The tandem repeats had already been studied individually, but it was difficult, as one gene had to be searched for at a time. Since there can be a million tandem repeats in the genome, pinpoint the tandem repeats that actually contribute to autism it would have been like looking for a needle in a haystack.
"In this study, we pioneered a method that can effectively search and analyze terabytes of whole genome sequencing data to find tandem repeats," he said. Yuen. "Many of the genes linked to these repetitions had never been considered among those involved in autism."
Some of the new genes identified include those involved in the nervous system. And the location of tandem repetition within the DNA itself is associated with "certain characteristics and behaviors such as IQ and life skills," reads the press release. "This is really a game changer for autism and genomic research," Yuen said. “It opens up new opportunities in diagnostics and precision medicine”.
Anomalies in DNA like music
One of the really interesting discoveries made in this study is the identification of about a million different points in the human genome capable of expanding and contracting. “It's a bit like an accordion. If they stretch to some extent, the music being played by the DNA or the instrument has a different tone. "
Scherer, who has been studying autism spectrum disorders for nearly two decades, is thrilled with the findings.
This is the most exciting progress we have had in 15 years.
Stephen Scherer
The implications of this discovery on autism
The discovery may lead to improvements in genetic testing, a boon for families and individuals with autism spectrum disorder who wish to answer a key question: Why? Yuen believes this research "will impact thousands of families" and will allow scientists to provide countless autistic individuals with a clear explanation of their autism by looking at their genes. "People with autism can also have serious medical conditions," he added. "So identifying these tandem reps can provide crucial information for families and caregivers."
Also Kristen Ellison, who lives in Cobourg, Ontario, is excited about the study. Her son, Carter, is nine years old and is autistic. Autism was diagnosed when he was only two years old. "We are at the beginning of this research and I don't know if it will have an immediate impact," he says. "But I hope one day it will improve the quality of life of people with autism."
Multiple types of autism
Another corollary to the discovery is that it actually adds at least 15 new types of autism. "Depending on the type of autism you have," says Scherer, you can think of activating a type of approach or treatment. Researchers suspect that these genetic wrinkles may play a role in other complex brain-related conditions such as epilepsy and schizophrenia.
Now that scientists have the tools to identify these "wrinkles" in DNA, they can try to find a way to fix them. "This is a major scientific advance in understanding autism and it will change lives," said Scherer.
