Better understanding the genetic variants associated with dyslexia could lead to a test that assesses whether a child is predisposed to have it
In the largest genetic study of dyslexia to date, scientists have identified 42 genetic variants that may influence a person’s chance of having it.
Dyslexia, which affects up to 1 in 10 people in the UK alone to some extent, often affects a person’s ability to read, write and spell.
Although the exact cause is unknown, previous research suggests dyslexia is inherited, with smaller studies linking it to a few genes.
To get a wider view of dyslexia’s potential genetic associations, Michelle Luciano at the University of Edinburgh, UK, and her colleagues carried out a genome-wide association study on 1.1 million adults, mainly of European origin, of whom 51,000 said they had been diagnosed with dyslexia. These studies involve scanning markers across the complete sets of genomes of many people to find any variations associated with a particular trait or condition.
The researchers identified 42 genetic variants that tended to differ between the participants who did and did not have dyslexia. The more of these variants an individual had, the higher their chance of having dyslexia, the results suggest.
Referring to dyslexia, Luciano says: “It’s a complex trait and like lots of complex traits, it’s influenced by many genes, and each of them by itself has a very small effect on the increasing genetic predisposition of dyslexia.”
To confirm their results, the researchers created a scoring system for a separate group of 2800 adults and teenagers, based on their dyslexia-associated variants.
A higher score was linked to these participants showing more signs of dyslexia on a reading and spelling test. It isn’t known whether any of the 2800 participants had been diagnosed with dyslexia.
Around one-third of the 42 genetic variants have previously been linked to conditions such as attention deficit hyperactivity disorder. The remaining links were more novel, with some of these variants also being associated with a lower pain threshold and being ambidextrous.
The genetic variants may alter a neurodevelopmental process, says In-Hyun Park at Yale University. This could then affect multiple connections between a person’s neurons, which may cause dyslexia, pain sensitivity and ambidexterity, he says.
The 42 genetic variants may not cause dyslexia per se, but could make it more likely to occur if combined with certain learning styles, says Luciano. For example, phonics teaches children to match certain letters with sounds and may be particularly helpful for people with dyslexia, she says.
“When people think of genetics, the first thing they might think is that it’s something that’s fixed and we know that that’s simply not the case,” she says. “Genes operate within environments, so the environment is really important to consider.”
While much more research is required, the findings could one day lead to a genetic test that identifies children who are predisposed to have dyslexia, says Luciano. This could allow for interventions that reduce the development of reading and writing difficulties, she says.