A gene implicated in autism may also play a role in a common childhood language disorder, according to a new study.

Specific language impairment or SLI affects an estimated two to seven per cent of preschool children, who develop unexplained difficulties in producing and understanding language. It is as common as dyslexia, the researchers said.

"This is the first time anyone has pinpointed a specific gene that is involved in common forms of language impairments," said University of Oxford geneticist and Wellcome Trust researcher Simon Fisher, who led the study

In Wednesday's online issue of the New England Journal of Medicine, Fisher and his colleagues reported that children from 184 families who had variants of the CNTNAP2 gene showed reduced language abilities like those found in SLI, such as repetition of nonsense words.

To identify the CNTNAP2 variants, the researchers looked for genes that are switched on and off in the brain by a different gene called FOXP2.

Mutations of FOXP2 also appear to play a role in rare cases of severe speech and language disorder.

Interferes with nervous system protein?

Similar changes in the regulation or function of CNTNAP2 could be involved in the language problems in both SLI and autism, Fisher said.

"This supports the emerging view that autism involves the convergence of a number of distinct problems underpinned by different genetic effects," he added.

The researchers do not know how the mutations interfere with language development. One possibility is that changes in CNTNAP2 interferes with the production of the neurexin protein, which is important in developing the nervous system and the "language-ready brain," Fisher said.

Language disorders are important in terms of reaching educational and social goals, but are often neglected, said Prof. Dorothy Bishop, who was not involved in the study but specializes in children's communication impairments at the University of Oxford.

"This landmark study provides an important first step in unravelling the complex biological factors that determine susceptibility to language difficulties," Bishop said.

With files from Reuters