AUTISM IS NOT JUST A DISORDER OF THE BRAIN, MOUSE STUDY SUGGESTS

Autism spectrum disorders (ASDs) are characterized by impaired social interactions and repetitive behaviors, often accompanied by abnormal reactions to sensory stimuli. ASD is generally thought to be caused by deficits in brain development, but a study in mice suggests that at least some aspects of the disorder, including how touch is perceived, anxiety, and social abnormalities are linked to defects in another area of the nervous system, the peripheral nerves found throughout the limbs, digits, and other parts of the body that communicate sensory information to the brain.

In the new study, the researchers examined the effects of gene mutations known to be associated with ASD in humans. In particular, they focused on Mecp2, which causes Rett syndrome, a disorder that is often associated with ASD, and Gabrb3, which also is implicated in ASD. They looked at two other genes connected to ASD-like behaviors as well.

These genes are believed to be essential for the normal function of nerve cells, and previous studies have linked these mutations to problems with synaptic function, how neurons communicate with each other.

"Although we know about several genes associated with ASD, a challenge and a major goal has been to find where in the nervous system the problems occur," researcher says. "By engineering mice that have these mutations only in their peripheral sensory neurons, which detect light touch stimuli acting on the skin, we've shown that mutations there are both necessary and sufficient for creating mice with an abnormal hypersensitivity to touch."

The investigators measured how the mice reacted to touch stimuli, such as a light puff of air on their backs, and tested whether they could discriminate between objects with different textures. Mice with ASD gene mutations in only their sensory neurons exhibited heightened sensitivity to touch stimuli and were unable to discriminate between textures. The transmission of neural impulses between the touch-sensitive neurons in the skin and the spinal cord neurons that relay touch signals to the brain was also abnormal. Together, these results show that mice with ASD-associated gene mutations have deficits in tactile perception.

Thanks to: sciencedaily.com