Genes May Be To Blame For Poor Reading Skills
New research from the University of Oxford suggests that a common genetic variant may be partly responsible for poor reading ability.
Nearly 15 percent of people carry the variant, which is already associated with dyslexia, a learning disability that affects the development of literacy and language skills. Â
The Oxford researchers, based at the Wellcome Trust Centre of Human Genetics, found people carrying the sequence tended to perform lower than average in reading tests. However, the study found no impact on overall intelligence.
Previous research has identified at least six candidate genes that seem to influence the chances of a person developing dyslexia. The most likely of these genes, according to at least three separate studies, is one known as KIAA0319, which lies on chromosome six.
Their work highlighted a DNA sequence called a haplotype that included part of the critical gene. In the current study, researchers examined the link between this haplotype and reading ability in 6,000 children ages 7 to 9 years old who were participating in the Avon Longitudinal Study of Parents and Children (ALSPAC).
"On average, people carrying this common genetic variant tended to perform poorly on tests of reading ability,” Dr Silvia Paracchini, the study’s lead researcher, told BBC News.
"However, it’s important to note that this is only true for reading ability and not for IQ, so it doesn’t appear to be connected to cognitive impairment."
Dr Paracchini said that while small, the effect of the genetic variant was indeed statistically significant.
The team had previously found that this same haplotype is linked to reduced activity of the KIAA0319 gene during fetal development, acting in effect like a dimmer switch that reduced the power of the gene to do its normal job during development. This impacts development of the fetus’ cerebral cortex, the area of the brain responsible for thought processes.
Animal studies have shown that switching off KIAA0319 affects neuronal migration, the process that lets nerve cells created in the inner layer of the cerebral cortex area migrate outwards to their ultimate destination.
"This is clearly only part of the jigsaw puzzle that explains why some people have poorer reading ability than others or develop dyslexia,” Dr Paracchini said.
"There are likely to be many other contributing factors, but our research provides some valuable clues.
"We need to carry out studies into the exact role that this gene plays in brain development and how this affects people’s reading ability."
Professor Margaret Snowling, vice president of the British Dyslexia Association, told BBC News that other genes and environmental factors are likely involved in determining reading ability.  She also emphasized that some people are able to compensate and enjoy successful careers despite carrying this particular gene variation.
The study was published in the American Journal of Psychiatry.
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