For many of us, reading a book or a webpage is second nature. But for the 5–10% of school-aged children with dyslexia, the process of decoding words can be a significant challenge. Now, a new study—the largest of its kind to date—has expanded our understanding of the genetic foundations of reading and dyslexia, uncovering dozens of previously unknown genetic factors.
What We Already Knew
Previous research, using data from consented 23andMe research participants, had already successfully identified 42 genetic variants linked to a self-reported dyslexia diagnosis and showed that many of those genetic variants were also linked to cognitive ability and educational attainment.
This earlier work also supported a key idea: dyslexia isn’t a biologically distinct condition, but rather represents the lower end of a continuous spectrum of reading ability that varies naturally across the population.
A Bigger, Bolder Approach
So, how do you find even more subtle genetic clues? You build a more powerful magnifying glass.
In this latest effort, researchers used a method, called multi-trait analysis of GWAS (MTAG), to combine the statistical power of two massive datasets:
- The GenLang Consortium’s study on reading skill (involving ~27,000 people).
- The 23andMe study on dyslexia (involving over 1.1 million research participants).
By merging the results, scientists created an effective sample size of over 1.2 million individuals, dramatically boosting their power to detect genetic variants associated with dyslexia.
Landmark Discoveries
The results from this powerful analysis represent a leap forward in our understanding of the genetics of dyslexia and reading ability.
Dozens of New Genetic Loci
The study found 80 independent genome-wide significant regions linked to dyslexia. Of those, 36 had never been found by previous studies. Even more exciting, 13 of these regions were completely novel, with no prior known association with dyslexia.
Clues in Brain Development
Digging deeper, many of the genes located in these newly identified regions play a role in early brain development. Specifically, they are highly active in neuronal pathways, especially during embryonic brain development. This adds new clues to how the brain may be wired for reading ability.
An Evolutionary Angle
Interestingly, the researchers looked to see if there was evidence that the genetic factors influencing dyslexia have been subject to recent evolutionary pressure and found none. This suggests that these variants were not specifically selected for or against as humans transitioned from hunter-gatherer societies to agricultural ones in Europe.
The Big Picture and What’s Next
This research expands our map of the genetic landscape of dyslexia. By identifying the biological pathways involved, it opens new avenues for future research into why reading is difficult for some people and how we might develop better support strategies.
It’s crucial to remember that genes are not destiny. The research team created a polygenic index—also called a polygenic score—that tallies the effects of many different genetic variants. This index was able to predict between 2.3% and 4.7% of the variance in reading skills in a separate, independent group of individuals. Meaning that there may be other genetic factors, but also education, environment, and support systems that help determine reading skills.
Finally, like much genetic research, this work was conducted primarily in people of European descent. A critical next step is to conduct similar large-scale studies in more diverse populations to ensure that the insights and potential benefits of this research can apply to everyone.
