Scientists have identified 42 genetic variants that might influence a person’s chance of having dyslexia, in the largest genetic study of the condition to date, which could lead to a test that assesses whether a child is predisposed to have it.
Although the exact cause is unknown, previous research suggests dyslexia is inherited, with smaller studies linking it to a few genes.
Dyslexia is known to run in families – partly because of genetic factors – but until now, little was known about the specific genes relating to the risk of it developing.
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 1.1m 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, reports New Scientist.
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 2 800 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 2 800 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 adds.
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.
“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.
Study details
Discovery of 42 genome-wide significant loci associated with dyslexia
Catherine Doust, Pierre Fontanillas, Else Eising, Scott D. Gordon, Zhengjun Wang,
Gökberk Alagöz, et al
Published in Nature Journal on 20 October 2022
Abstract
Reading and writing are crucial life skills but roughly one in ten children are affected by dyslexia, which can persist into adulthood. Family studies of dyslexia suggest heritability up to 70%, yet few convincing genetic markers have been found. Here we performed a genome-wide association study of 51,800 adults self-reporting a dyslexia diagnosis and 1,087,070 controls and identified 42 independent genome-wide significant loci: 15 in genes linked to cognitive ability/educational attainment, and 27 new and potentially more specific to dyslexia. We validated 23 loci (13 new) in independent cohorts of Chinese and European ancestry. Genetic etiology of dyslexia was similar between sexes, and genetic covariance with many traits was found, including ambidexterity, but not neuroanatomical measures of language-related circuitry. Dyslexia polygenic scores explained up to 6% of variance in reading traits, and might in future contribute to earlier identification and remediation of dyslexia.
Nature article – Discovery of 42 genome-wide significant loci associated with dyslexia (Open access)
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