Finns point to dyslexia

Gene hint to human reading ability.
30 April 2003

HELEN PEARSON

Up to 15% of people may have dyslexia. © Corbis

A Finnish family has given the first clear clue to a gene involved in dyslexia.

Between 5 and 15% of people are dyslexic. They have problems reading, writing and spelling. Although scientists have suspected that genes are involved, they had not come up with a convincing candidate - until now.

One gene is mutated in around 10% of Finnish dyslexics, compared with 2-3% in the rest of the population, Juha Kere of the University of Helsinki, Finland and his team found. "If you have the gene you become more susceptible, but you're not necessarily dyslexic," he says.

Chimps, gorillas and other apes carry a slightly different form of the gene to humans, Kere told this week's Human Genome Organisation meeting in Cancún, Mexico. This implies that, during human evolution, a gene with some other function might have been adapted for processing words.

Exactly what the gene, dubbed DYXC1, does is still a mystery. Kere suspects that it may switch other genes on and off in the brain. They stumbled across it in a Finnish family containing four dyslexics whose chromosomes were all severed at the same point, disrupting DYXC1.

Such families are "a classical way of getting genes", says Mark Lathrop of the National Genotyping Centre in Evry near Paris, France. The discovery now has to be confirmed in other, larger populations, he says, before it can be branded a 'dyslexia gene'.

This could be tricky: countries with different languages use different word tests to diagnose dyslexia. Thus many underlying brain problems, with different genetic causes, might be branded with the same name.

Genetic gold-mine

Small, isolated populations around the world are a gold-mine for geneticists. Because they grew from only a handful of founders, it is easier to find shared mutations involved in disease. "Most mutations happened once in history," says Tom Hudson of McGill University in Montreal, Canada.

Hudson's research in a remote region of Quebec, for example, is revealing risk genes for heart disease and diabetes. And the Mediterranean island population of Sardinia is providing clues about susceptibility genes for asthma, the meeting heard.