SUNDAY July 13, 2008 (foodconsumer.org) -- The long hunt for gene mutations responsible for autism has finally borne some fruit. Researchers identified six genes which when mutated contribute to autism.

The six genes were found in Middle Eastern families, meaning how relevant the findings are to the U.S. general population remains unknown.

The study was conducted by Christopher Walsh, at Beth Israel Deaconess Medical Center and at Children's Hospital Boston, in collaboration with scientists and physicians in the United States, Turkey, Saudi Arabia, Pakistan, and Kuwait and the results were published on July 12, 2008 in the journal Science.

To increase the success chance of finding autism genes, the researchers focused on large families in which both parents share a recent ancestor, which made the gene-hunting much easier.

Autism is a spectrum of disease sharing three key traits: patients are slow to develop language, they are poor at social skills, and they repeat stereotyped behaviors over and over again.

The disorder can be caused by variations in a wide variety of genes.   All individuals with autism may have different gene mutations making it difficult to find the genetic causes for the disorder.

Researchers agree that the causes of autism are largely genetic. “At the moment, we understand the genetic causes of 15 to 20 percent of autism," Walsh said. "The remaining 80 percent remain unexplained,” said Walsh.

Autism was a rare disorder in the United States a couple of decades ago. Now according to the Centers for Disease Control and Prevention that one in every 150 children suffers the condition.

A health observer affiliated with foodconsumer.org cautioned that just because the disorder is related to genetic mutations does not mean people cannot do anything about it.

He suggested during the last couple of decades, spontaneous mutations may not have caused so much change in human genome that they make people so susceptible for autism in the country. There must be some things else also responsible for the increased prevalence.

For the study, the six genes were found after the researchers compared the genomes of autistic and non-autistic siblings. Middle Eastern families are often larger with an average family having six children, making the comparison possible.

The study involved 88 families from eight countries: Jordan, Saudi Arabia, Kuwait, Oman, Pakistan, Qatar, Turkey, and the United Arab Emirates.

The researchers found deletions, a type of gene mutation, in five of studied families (5.6%).   Those who had two copies of genes missing had autism while those who had only one copy missing did not.

Many of the deletions inactivate genes involved in learning, Walsh said. They change nerve cells in their synapses that underlie learning and the formation of new memories.

Walsh and colleagues also found that the deletions also alter gene activity.

"Only one of these deletions completely removed a gene," he said. The others removed areas close to the genes that contain the genes' "on/off switches."

The good news for those who had deletions that affect genes "on/off switches" is that this type of autism can be improved through exposure to certain environments. For instance, enriched learning environments are known to help some autistic children overcome the disorder.