Patterns Provide New Autism Clues
Published Jun 10, 2011 8:30 AM
For decades, autism researchers have faced a baffling riddle: how to unravel a disorder that leaves no known physical trace as it develops in the brain.
Now a UCLA study is the first to reveal how the disorder makes its mark at the molecular level, resulting in an autistic brain that differs dramatically in structure from a healthy one. Published May 25 in the online edition of Nature, the findings provide new insight into how genes and proteins go awry to alter the mind.
The discovery also identifies a new line of attack for autism researchers, who currently face a vast array of potential fronts for tackling the neurological disease and identifying its diverse causes.
"If you randomly pick 20 people with autism, the cause of each person's disease will be unique," says principal investigator Dr. Daniel Geschwind, a professor of neurology and psychiatry at UCLA's David Geffen School of Medicine.
"Yet when we examined how genes and proteins interact in autistic people's brains, we saw well-defined shared patterns," Geschwind explains. "This common thread could hold the key to pinpointing the disorder's origins."
A complex brain disorder that strikes in early childhood, autism disrupts a child's ability to communicate and develop social relationships; it's often accompanied by acute behavioral challenges. In the United States; autism spectrum disorders are diagnosed in one in 110 children — and one in 70 boys. Diagnoses have expanded tenfold in the last decade.
Led by Geschwind and comprising scientists from UCLA, the University of Toronto and King's College London, the research team 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 most evolved part of the human brain, the cerebral cortex.
The researchers focused on gene expression — that is, how a gene's DNA sequence is copied into RNA, which directs the synthesis of cellular molecules called proteins. Each protein is assigned a specific task by the gene to perform in the cell.
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," says first author Irina Voineagu, a UCLA postdoctoral fellow in neurology. "From a molecular perspective, half of these brains shared a common genetic signature."
Given the numerous causes of autism, Voineagu says, "this was an unexpected and exciting finding."
For the latest on autism diagnoses, treatments, family counseling and more, check the UCLA Center for Autism Research and Treatment.
The next step for the researchers was to identify 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 healthy brains' frontal and temporal lobes, they saw that more than 500 genes were expressed at different levels in the two regions.
In the autistic brains, however, 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 says. "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."
Other clear-cut patterns emerged, as well, when the autistic and healthy brains were compared.
To find out more, click here.
This article originally appeared in UCLA Today May 25, 2011.