A boy with autism is seen at a treatment center. French researchers have discovered a new gene linked to autism, a mental disability which prevents sufferers from communicating and forming relationships normally and whose causes are unknown.[Photo: AFP]

French scientists have identified genetic mutations in a small number of children with autism which could provide insight into the biological basis of the disorder.

They sequenced a gene called SHANK3 in more than 200 people with autism spectrum disorders (ASD), which includes autism, and found mutations in the gene in members of three families.

ASD covers a range of problems that affect communication, social interaction, verbal skills and behavior.

"These mutations concern only a small number of individuals, but they shed light on one gene ... that is involved in autism spectrum disorders," Thomas Bourgeron, of the Pasteur Institute in Paris, said in a report in the journal Nature Genetics.

ASD, which affect six out of 1,000 children, range from mild to severe forms. The disorders are caused by chromosomal rearrangements in 3 to 6 percent of cases.

In people with cognitive deficits and with autistic behavior a part of their chromosome 22 is often affected. That region contains the SHANK3 gene.

In all three families identified in the study, the researchers found they had various types of mutations in the gene. Two brothers in one family had small deletions, while another child in a different family had significant deletions.

A girl with a deletion of SHANK 3 in the third family suffered from autism while her brother, who had an additional copy of the gene, had a mild form of autism called Asperger syndrome.

The cause of autism is unknown. It usually develops before the age of 30 months. A minority of autistic children, who are known as autistic savants, show remarkable artistic, musical or mathematical skills.

The protein encoded by SHANK3 interacts with other proteins called neuroligins, which have a role in giving impulses to the brain, spinal column and nerves.