"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. "From a molecular perspective, half of these brains shared a common genetic signature. Given autism's numerous causes, this was an unexpected and exciting finding."
The researchers' next step was to identify the common patterns. To do this, they looked at the cerebral cortex's frontal lobe, which plays a role in judgment, creativity, emotions and speech, and at its temporal lobes, which regulate hearing, language and the processing and interpreting of sounds.
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.
"In a healthy brain, hundreds of genes behave differently from region to region, and the frontal and temporal lobes are easy to tell apart," Geschwind said. "We didn't see this in the autistic brain. Instead, the frontal lobe closely resembles the temporal lobe. Most of the features that normally distinguish the two regions had disappeared."
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.
"Several of the genes that cropped up in these shared patterns were previously linked to autism," said Geschwind. "By demonstrating that this pathology is passed from the genes to the RNA to the cellular proteins, we provide evidence that the common molecular changes in neuron function and communication are
|Contact: Elaine Schmidt|
University of California - Los Angeles