Brains from people with autism show patterns of gene expression similar to those from people with schizophrenia, according to a new analysis.
The findings, published May 24 in Translational Psychiatry, deepen the connections between the two conditions, says study leader Dan Arking, associate professor of genetic medicine at Johns Hopkins University in Baltimore, Maryland.
People who have either autism or schizophrenia share features such as language problems and difficulty understanding other people’s thoughts and feelings. They also have genetic risk factors in common. “And now I think we can show that they share overlap in gene expression,” Arking says.
The study builds on previous work, in which Arking’s team characterized gene expression in postmortem brain tissue from 32 individuals with autism and 40 controls. In the new analysis, the researchers made use of that dataset as well as one from the Stanley Medical Research Institute that looked at 31 people with schizophrenia, 25 with bipolar disorder and 26 controls.
They found 106 genes expressed at lower levels in autism and schizophrenia brains than in controls. These genes are involved in the development of neurons, especially the formation of the long projections that carry nerve signals and the development of the junctions, or synapses, between one cell and the next. The results are consistent with those from previous studies indicating a role for genes involved in brain development in both conditions.
“On the one hand, it’s exciting because it tells us that there’s a lot of overlap,” says Jeremy Willsey, assistant professor of psychiatry at the University of California, San Francisco, who was not involved in the work. “On the other hand, these are fairly general things that are overlapping.”
Most previous studies of gene expression in autism or schizophrenia did not involve brain tissue: Some relied on blood and others on neurons derived from stem cells. “Having what the brain transcriptome looks like is important,” says Jon McClellan, professor of psychiatry at the University of Washington in Seattle, who was not involved in the work.
It’s also significant that the common patterns emerged from two disparate datasets involving different study designs and brain regions. “The fact that you have a positive finding, to me, under those circumstances, really says that this is likely to be real,” Arking says.
In the study, gene expression in schizophrenia and bipolar disorder are not notably similar, even though schizophrenia is thought to have stronger genetic ties to bipolar disorder than to autism. A larger study may reveal an overlap between the two conditions, Arking and others say.
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