WEDNESDAY, May 25 (HealthDay News) -- The symptoms and severity
of autism vary widely, but new research shows remarkable
similarities at the molecular level in the brains of people with
Researchers from Los Angeles, Toronto and London analyzed
post-mortem brain tissue samples from 19 people with autism and 17
In the healthy brains, researchers saw distinct differences in
the gene expression in the frontal lobe vs. the temporal lobe of
the cerebral cortex -- differences that help determine the
structure and function of the two brain regions.
Specifically, between the frontal and temporal lobes in the
healthy brains, more than 500 genes were expressed at different
levels. Gene expression is the process by which a gene's DNA
sequence is copied into RNA to produce proteins, which perform
specific tasks within the cell.
But researchers didn't find those same patterns in autistic
brains. Instead, researchers found only eight differences in the
gene expression in the frontal and temporal lobes.
"In a healthy brain, the frontal and temporal lobes can be differentiated," said principal investigator Dr. Daniel Geschwind, a distinguished professor of neurology, psychiatry and human genetics at the David Geffen School of Medicine at UCLA. "But in autism we didn't see that. Instead, the frontal lobe closely resembles the temporal lobe."
Many of those regional differences in the cerebral cortex are
established during fetal development, researchers added.
The study is published in the May 25 online issue of
Over the past decade, researchers have discovered lots of gene
variants that seem to play a role in some cases of autism, but none
of the mutations were present in a large percentage of people with
Prior research has also implicated regions of the cerebral
cortex, which is highly developed in humans, in autism. The frontal
lobe is involved with judgment, language, planning, social
cognition and personality, while the temporal lobe is important for
language and emotions, Geschwind said.
But this is the first study to show differences in the patterns
of gene expression between brain regions. It's those patterns of
gene expression that enable the brain to function normally and to
communicate properly with other regions of the brain, explained
Robert Ring, vice president for translational research for Autism
"This study allows us to look at the complexity of what's going on at a molecular level in the brain, a step up from the gene," Ring said. "Here we have the opportunity to really see that the development of normal brain physiology requires differences in the regional activity of gene networks. This report provides evidence that the expected pattern of these differences is absent in autism."
Researchers say the findings may help in the development of
medications that target the pathways. "The fact that it's shared
says there is some hope of beginning to unwind this and develop
some treatments that would target those pathways," Geschwind
Compared to the healthy brains, autistic brains had less
activity in the genes responsible for neuron function and
communication, and a heightened level of gene expression in genes
involved in immune function and inflammatory response.
Some of those genes have also previously been implicated in
autism, researchers noted.
An estimated one in 110 U.S. children -- including one in 70
boys -- has an autism spectrum disorder, according to background
information in the study. Autism affects behavior and impairs the
ability to communicate and establish social relationships.
Diagnoses have increased tenfold in the past decade.
National Institutes of Health has more on autism.
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