Genetic link to autism may explain speech problems

London, Jan 12: Scientists have found a genetic link to autism that may explain why affected children can take months or even years longer to speak, a study says.

Variants in this gene could help to diagnose the condition and, in the long run, provide valuable insights into how to develop more effective treatments, the study said. ''Autism is a developmental brain disorder that impairs basic behaviours needed for social interactions, such as eye contact and speech, and includes other symptoms, such as repetitive, obsessive behaviours,'' said Prof Aravinda Chakravarti of the Johns Hopkins University School of Medicine, who conducted one of the studies. ''The symptoms sometimes cause profound disability, and they persist throughout life. Treatments may relieve some symptoms, but no treatment is fully effective in treating the core social deficits. Although the cause of autism is not yet clear, studies of twins have shown that genes play a major role,'' the Daily Telegraph quoted him as saying.

Intriguingly the variants identified mostly affect boys, especially when inherited from mothers. However, they are present in more than one third of the population, underlining how many genes contribute to the disorder and inheriting these gene variants does not mean that a boy will inevitably develop autism but will be more vulnerable to language-related problems, the research informed.The gene is most active in brain regions involved with thought and language, which suggests why affected children can have speech delayed, and the link with the developmental disorder is convincing because it has been confirmed by three teams of scientists.

The American Journal of Human Genetics published findings of a team led by Prof Daniel Geschwind at the University of California, Los Angeles, along with one by Prof Aravinda Chakravarti and Prof Dan Arking from the Johns Hopkins University School of Medicine, Baltimore, and a team at Yale led by Prof Matthew State.Confirmation by three groups, using different methods, suggested that several variants in the gene, called contactin-associated protein-like 2 (CNTNAP2), may play a key role in the development of autism. The gene makes a protein that enables brain cells to communicate with each other through chemical signals and appears to play a role in brain cell development. ''This gene not only may predispose children to autism,'' said Prof Geschwind, who searched for the gene in 500 affected families, ''but we think that it also may influence the development of brain structures involved in language, providing a tangible link between genes, the brain and behaviour.''

The UCLA team examined CNTNAP2's presence in early brain tissue and discovered that the gene was most active in developing brain structures involved in language and thought, especially the frontal lobe. ''Finding genes is a first step in trying to better understand the disorder, and that many genes are likely to contribute,'' Prof Geschwind said.The Hopkins team studied almost 1,500 affected children and found that children with autism were about 20 per cent more likely to have inherited the one gene variant from their mothers than from their fathers. ''For males, individuals who get the version of the gene linked with autism from mom have around 36 per cent increase in risk related to someone with no risk versions of the gene, and if the male child get the riskier version from both mom and dad, the risk increased by about 59 per cent,'' Prof Arking said.''Autism is highly heritable. Identifying the genes involved is crucial to our ability to map out the pathology of this isolating and sometimes terribly disabling disease, which currently has no cure,'' the director of the US National Institute of Mental Health, Dr Thomas Insel said.