The largest study ever conducted on the genetic basis of dyslexia has identified 42 variants in the genes that could influence the risk of suffering from this disorder.
Dyslexia, an unexpected difficulty in reading in children of normal intelligence, is the most frequent among the specific learning disorders and the most present among Italian school pupils. It is estimated in Italy that dyslexia affects between 2 and 4% of the population, but the numbers are not precise, because at school age, this disorder often escapes diagnosis (to learn more: what we know, so far, about dyslexia). It has long been assumed that this disorder is based – also – on a genetic predisposition and the new study, published in Nature Geneticshe wanted to investigate further.
Looking for answers. Scientists led by Michelle Luciano, a psychologist at the University of Edinburgh, conducted a study of whole genome association out of 1.1 million adults mainly of European descent, 51,000 of whom had received an official diagnosis of dyslexia. This method of investigation consists in looking for the genetic variants associated with a given disease in the entire genome of many individuals, comparing the DNA of healthy people with that of people who are affected by it.
© Daniel Britton
Significant alterations. The analysis made it possible to find 42 genetic variants that tend to differentiate those suffering from dyslexia from those not affected. The greater the number of variants of this group present in one’s genetic makeup, the higher the risk of having dyslexia. None of them is decisive because, as he explained to the New Scientist Michelle Luciano, dyslexia “is a complex condition that as such is influenced by many genes, each of which alone has a very small effect on increasing the genetic predisposition to the disease.”
It is not even correct to say that these alterations cause dyslexia. Rather, in people who carry them in their DNA, they can make it more likely to occur, for example under certain learning conditions. Luciano clarifies: «When one thinks of genetics, the first thing one might believe is that it is something immutable, fixed, while we know that it is not so. Genes operate within the environment, and therefore the environment is a very important factor to consider ».
Contact points. A third of the variants found were already known to researchers, because they are linked to ADHD, the Attention Deficit / Hyperactivity Disorder that involves problems with attention and concentration, impulse control and activity level.
The other variants are less well known, although some have been associated with a lower pain threshold or ambidextrousness.
One hypothesis is that these genetic variants involve an alteration of neurodevelopment, which could affect neural connectivity and give rise to dyslexia and the other conditions mentioned. However, research into the genetic underpinnings of dyslexia is still in its infancy: one day, discoveries like this could lead to genetic tests that identify the people most likely to develop it, and allow for early supportive interventions.