Scientists have for the first time discovered that the brains of people with autism are dramatically different in molecular structure than those of healthy people.
The findings provide new insight into how genes and proteins go awry in autism to alter the mind, and may help researchers tackle the neurological disorder and identify its diverse causes.
Autism is a complex brain disorder that strikes in early childhood. The disease disrupts a child's ability to communicate and develop social relationships and is often accompanied by acute behavioural challenges.
The research team, led by Daniel Geschwind, a professor of neurology and psychiatry at the David Geffen School of Medicine at UCLA included scientists from the University of Toronto and King's College London.
They compared brain tissue samples obtained after death from 19 autism patients and 17 healthy volunteers. After profiling three brain areas previously linked to autism, the group zeroed in on the cerebral cortex, the most evolved part of the human brain.
By measuring gene-expression levels in the cerebral cortex, the team uncovered consistent differences in how genes in autistic and healthy brains encode information.
"We were surprised to see similar gene expression patterns in most of the autistic brains we studied," said first author Irina Voineagu, a UCLA postdoctoral fellow in neurology.
When the scientists compared the frontal and temporal lobes in the healthy brains, they saw that more than 500 genes were expressed at different levels in the two regions.
In the autistic brains, these differences were virtually non-existent.
Two other clear-cut patterns emerged when the scientists compared the autistic and healthy brains.
First, the autistic brain showed a drop in the levels of genes responsible for neuron function and communication. Second, the autistic brain displayed a jump in the levels of genes involved in immune function and inflammatory response.
The study was published online in Nature.