Autism begins in pregnancy, according to study: Cortical layers disrupted during brain development in autism
Date:
March 26, 2014
Source:
University of California, San Diego Health Sciences
Postmortem analysis of autistic brain tissue revealed patch-like areas of disorganized neurons. Arrows show a patch of decreased or absent expression of genetic markers across multiple layers of the dorsolateral prefrontal cortex.
Credit: Rich Stoner, Ph.D., University of California, San Diego
Researchers at the University of California, San Diego School of Medicine and the Allen Institute for Brain Science have published a study that gives clear and direct new evidence that autism begins during pregnancy.
The study will be published in the March 27 online edition of the New England Journal of Medicine.
The researchers -- Eric Courchesne, PhD, professor of neurosciences and director of the Autism Center of Excellence at UC San Diego, Ed S. Lein, PhD, of the Allen Institute for Brain Science in Seattle, and first author Rich Stoner, PhD, of the UC San Diego Autism Center of Excellence -- analyzed 25 genes in post-mortem brain tissue of children with and without autism. These included genes that serve as biomarkers for brain cell types in different layers of the cortex, genes implicated in autism and several control genes.
"Building a baby's brain during pregnancy involves creating a cortex that contains six layers," Courchesne said. "We discovered focal patches of disrupted development of these cortical layers in the majority of children with autism." Stoner created the first three-dimensional model visualizing brain locations where patches of cortex had failed to develop the normal cell-layering pattern.
"The most surprising finding was the similar early developmental pathology across nearly all of the autistic brains, especially given the diversity of symptoms in patients with autism, as well as the extremely complex genetics behind the disorder," explained Lein.
During early brain development, each cortical layer develops its own specific types of brain cells, each with specific patterns of brain connectivity that perform unique and important roles in processing information. As a brain cell develops into a specific type in a specific layer with specific connections, it acquires a distinct genetic signature or "marker" that can be observed.
The study found that in the brains of children with autism, key genetic markers were absent in brain cells in multiple layers. "This defect," Courchesne said, "indicates that the crucial early developmental step of creating six distinct layers with specific types of brain cells -- something that begins in prenatal life -- had been disrupted."
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