Dyslexia, genes and labels

This week, BioNews includes details of a study that has uncovered a possible genetic influence on reading ability. What exactly have the researchers found, and what does it mean for children with reading difficulties? And is it really the 'dyslexia gene', as it was called in some of the newspaper story headlines? (1)

The genetic variation in question - a version of the KIAA0319 gene - was indeed originally identified through its association with dyslexia, a condition that affects the development of literacy and language related skills. This research provided the foundations for the latest study, which has showed that the same gene variant, present in 15 per cent of the population, is associated with poor reading ability in general, not just dyslexia.

These findings provide a good example of how research into disorders or 'conditions' may shed light on basic physiological or developmental processes - in this case, the acquisition of reading ability. Following the genetic studies on KIAA0319, further work on animals has shown that the protein encoded by this gene is involved in neuronal migration, the means by which nerve cells in the developing fetal brain reach their final destination.

Although the exact role of the gene in this highly complex process remains a mystery, the fact that a common version of KIAA0319 is associated specifically with reading ability, rather than general intelligence, suggests it is a crucial factor in the development of the brain circuitry responsible for this skill. But to call it the 'dyslexia gene', as some newspaper headline writers did, is somewhat misleading. For one thing, it is undoubtedly the case that many other genes and other non-genetic factors are involved in dyslexia, and thus in the acquisition of reading skills.

Secondly, it implies that only children with reading problems have this gene, whereas of course everyone has the gene, it is just that 15 per cent of the population happen to have inherited a particular version of it. Furthermore, calling genes after what happens when they don't work properly is misleading, and will become increasingly irrelevant as our knowledge increases about what our 20-25,000 genes all do in the body. As geneticists Tom Strachan and Andrew Read point out in their human molecular genetics textbook, labelling genes by what happens when they don't work properly is a bit like calling your freezer 'a machine for ruining frozen food'. Although they were referring to 'official' gene names, their comment applies equally to accounts of genetic discoveries in the news.