FRIDAY, Oct. 28, 2005 (HealthDay News) -- Researchers have identified a variation in a gene that appears to account for about 17 percent of cases of the reading disability dyslexia.
Experts hailed the finding as a potential milestone in the understanding of the widespread disorder.
"This is highly significant," said Jeffrey W. Gilger, associate dean for discovery and faculty development at Purdue University. "It is the first really good study that combines molecular genetics with brain imaging research, as well as actually testing whether these genes they think they found are really active in the brain."
Frank Wood, professor of neurology at Wake Forest University School of Medicine, added: "This study is the first one to make a connection between a gene that is known to be associated with dyslexia and an anomaly in brain development. The authors have persuasive evidence that this particular gene variant causes altered migration of neurons and therefore alters the structure of the brain. That's a very important step in the evolution of our understanding of the neurogenetics of dyslexia and it will lead to further steps."
Neither Gilger nor Wood were involved in the research, which appears in next week's issue of the Proceedings of the National Academy of Sciences. The findings were to be released Friday to coincide with a presentation at the meeting of the American Society of Human Genetics in Salt Lake City.
The study's senior author, Dr. Jeffrey Gruen, an associate professor of pediatrics at Yale University's Child Health Research Center, said genetic tests for the variant could start right away that might steer people to the appropriate educational treatments.
Other experts disagreed.
"The tendency is to want to jump on this, but tests aren't complex enough to find this blip, and they're also expensive," Gilger said.
"We don't yet know what factors determine whether people with this genetic variation do or don't end up with dyslexia," Wood added. "A host of environmental and genetic influences likely influences or determines whether somebody with this particular genetic variation ends up being dyslexic or not. And until the nature of some of those other influences is fully specified, we won't know what it means to say to somebody that their 5-year-old child has this particular genetic endowment."
In the future, however, this information may be useful in identifying people with this variant and administer some form of gene therapy, perhaps by giving pills or vitamins to compensate for the deficiency, Gilger said.
Dyslexia is one of the most common neurobehavioral disorders, affecting up to 17 percent of the population. Sufferers have trouble processing language-based information, making it difficult to learn to read, write and spell. Early educational interventions can help compensate for some of these difficulties.
Dyslexia has a strong genetic component, probably involving several genes, although not dozens, Gruen explained.
Dyslexia is also accompanied by alterations in the structure and functioning of the brain.
Researchers had already identified a region on chromosome 6 that might house some of these errant genes. The region contains about 19 genes, most of which are expressed in the brain.
Gruen and his colleagues genotyped members of 153 families and found a deletion in the DCDC2 gene on chromosome 6 that is the likely dyslexia culprit.
When the researchers inhibited production of the gene in rat embryos, they found that doing so had influenced the development of neurons, or brain cells, causing them to migrate shorter distances.
"That fits perfectly with physiologically what we see," Gruen said. "We're seeing a disruption of the normal reading circuits, and what makes up these reading circuits are going to be neurons," Gruen said.
Since then, the researchers have found the deletion in children, as have two other research groups, one in Finland and one in Germany.
Functional MRIs conducted in humans revealed that the gene was expressed in reading centers of the brain. "Dyslexics use alternate circuits and alternate pathways, the thought being that the circuits for normal reading are disrupted and alternative pathways are less efficient," Gruen said.
Whether or not these findings translate into concrete gains for people with dyslexia, the research sends "a very important message to educators, parents and children, which is that you're not dumb. This isn't your fault. You're not a bad parent," Gruen said. "This is a transmitted difference in our gene that makes one person learn differently than another. That's all it is."
More information
Learn more about dyslexia from the National Institute of Neurological Disorders and Stroke.
