UCSD researchers discover that autistic children are missing key genetic markers in the cerebral cortex.
A recent study led by professor of neurosciences and Director of the UCSD Autism Center of Excellence Eric Courchesne and Doctor Ed S. Lein of the Allen Institute for Brain Science in Seattle reveals the possibility that autism can arise during a baby’s early development in the womb.
The New England Journal of Medicine published the findings of the study in its March 27 online edition, detailing how the researchers analyzed over 25 different genes in brain tissues of children with and without autism post-mortem.
Some of the specifically chosen genes acted as biomarkers for brain-cell types in distinct layers of the cortex. These genes are known as control genes.
In early brain development, the brain cells in each cortical layer develop into specific types, each with a unique pattern of brain connectivity that plays an essential role in processing information.
The researchers analyzed the six layers of the cortex for any abnormalities in the early development of these brain cells in each specific cortical layer. They discovered that in children with autism, vital genetic markers were missing in brain cells of multiple cortical layers.
“This defect,” Courchesne said in an April 3 UCSD News Center article, “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.”
The lack of such genetic markers greatly affects the frontal cortex and the temporal cortex of the brain, giving insight into why autistic individuals display a different array of symptoms. The frontal cortex is crucial to communication and understanding of social cues while the temporal cortex pertains to language.
However, the visual cortex that is associated with perception and is usually not affected by autism shows no signs of the disruptions found in the frontal and temporal cortices.
Due to the findings of the study, scientists have come closer to discovering what may trigger autism to develop, a task that often requires scientists to study adult brains.
“The fact that we were able to find these patches is remarkable,” Lein said. “This suggests that these abnormalities are quite pervasive across the surface of the cortex.”
Although the researchers have yet to discover the cause of why the defects occur, they stressed the significance of the fact that the defects were found at focal patches of the cortex, indicating that the abnormalities are not uniform throughout the cortex.
“The finding that these defects occur in patches rather than across the entirety of cortex gives hope as well as insight about the nature of autism,” Courchesne said.
Since the defects occur in patches, the study supports the notion that the brains of young, autistic children can rewire connections to make up for the losses in early development. It also explains why toddlers diagnosed with autism show immediate improvement upon early treatment — a result that has scientists hopeful of answering the question of how the recovery of these connections occur.
