Autism, a social disorder often accompanied by abnormal reactions to sensory stimuli, is not just caused by deficits in brain development, a study in mice suggested Thursday.

The study, published in the U.S. journal Cell, said that some aspects of the disorder are linked to defects in nerves found in the limbs, digits and other parts of the body that communicate sensory information to the brain.

Symptoms including being sensitive to touch, anxiety, and social abnormalities, it said, might occur as a result of problems with the so-called peripheral nerves.

In the study, researchers examined the effects of gene mutations known to be associated with autism in humans.

They engineered mice that have these mutations only in their peripheral sensory neurons, which detect light touch stimuli acting on the skin.

The results showed that mutations there are both necessary and sufficient for creating mice with an abnormal hypersensitivity to touch.

The researchers next examined anxiety and social interactions in the mice using established tests looking at how much mice avoided being out in the open and how much they interacted with mice they'd never seen before.

Surprisingly, the animals with autism gene mutations only in peripheral sensory neurons showed heightened anxiety and interacted less with other mice.

"Although we know about several genes associated with ASD (autism spectrum disorder), a challenge and a major goal has been to find where in the nervous system the problems occur," senior author David Ginty, professor of neurobiology at Harvard Medical School, said in a statement.

"An underlying assumption has been that ASD is solely a disease of the brain, but we've found that may not always be the case," said Ginty, also a Howard Hughes Medical Institute investigator

source : xinhua