Scientists have announced that they have identified a gene for dyslexia, paving the way for the development of earlier tests for the reading disability.
Accurate diagnosis at a younger age of the condition that affects up to 10 million people in Britain is essential for the development of effective educational programmes, researchers said.
Many children who are poor readers are mistakenly diagnosed as a dyslexic when their reading ability is not assessed alongside their intelligence. The sign of real dyslexia is a reading ability well below that for the child's age and intelligence. A comparison of the genetic make-up of 153 dyslexic families carried out at Yale School of Medicine in the US showed that a single gene could be responsible for up to one in five cases of the condition.
The researchers found that an alteration in the gene on chromosome six, called DCDC2, led to disruption in the formation of brain circuits that make it possible to read.
The findings were presented at a meeting of the American Society of Human Genetics in Salt Lake City, Utah, yesterday and published simultaneously in the Proceedings of the National Academy of Sciences. Jeffrey Gruen, associate professor of paediatrics at Yale, who led the study, said: "These promising results now have the potential to lead to improved diagnostic methods to identify dyslexia and deepens understanding of how the reading process works on a molecular level."
Learning to read involves brain circuits learning to communicate with one another. In people with reading disabilities these circuits are disrupted. People with dyslexia form compensatory brain circuits but they are inefficient and they have difficulty learning to read.
Previous research over the past 30 years has shown that dyslexia has a strong hereditary component. Up to half the children of dyslexic parents and half the siblings of dyslexic children are also affected. In the search for a genetic cause, attention has focused on chromosome six ,which contains 19 genes, most of which affect functions in the brain. In experiments on rats, the Yale team found that the gene DCDC2 was activated in both fluent and dyslexic readers, suggesting dysfunction of the gene caused the reading disability.
Professor Gruen said: "We now have strong statistical evidence that a large number of dyslexic cases - perhaps as many as 20 per cent - are due to the DCDC2 gene. The gene is expressed in reading centres of the brain where it modulates migration of neurons. This very architecture of the brain circuitry is necessary for normal reading.
"We can't continue with one-size-fits-all schooling any more. People with dyslexia are not less intelligent than others, they just learn in different ways. Tailoring programmes to fit the needs of these children will enhance their success in school."
The researchers say other genes yet to be identified are involved in dyslexia. Brain scans carried out by researchers from the UK Dyslexia Research Trust have shown that people with dyslexia have underactive brains in areas associated with reading and vocal word formation.
However, other research indicates that dyslexia may also be a neurological condition. Post-mortem studies of the brains of people with dyslexia showed that many neurons were in the wrong place.
Difficulties with words
* The word dyslexia comes from the Greek, meaning"difficulty with words".
* Around 4 per cent of the population is severely dyslexic, and up to a further 13 per cent suffer mild problems.
* The condition affects people from all backgrounds and of all abilities, from those with a rudimentary education to those with university degrees.
* It causes hesitant reading, difficulty with sequences such as getting dates in order, poor organisation and erratic spelling.
* People with dyslexia may also be innovative thinkers, good trouble shooters, intuitive problem solvers and lateral thinkers.
* Successful dyslexics include the physicist and Nobel Prize- winner Albert Einstein, Winston Churchill and the author Hans Christian Andersen.Reuse content