Genetic studies find dysregulation in pathways that govern development of the prefrontal cortex in young patients with autism
A study led by Eric Courchesne, PhD, director of the Autism Center of Excellence at the University of California, San Diego School of Medicine has, for the first time, identified in young autism patients genetic mechanisms involved in abnormal early brain development and overgrowth that occurs in the disorder. The findings suggest novel genetic and molecular targets that could lead to discoveries of new prevention strategies and treatment for the disorder.
The study to be published on March 22 in PLoS Genetics uncovered differences in gene expression between brain tissue from young (2 to14 years old) and adult individuals with autism syndrome disorder, providing important clues why brain growth and development is abnormal in this disorder.
Courchesne first identified the link between early brain overgrowth and autism in a landmark study published by the Journal of the American Medical Association (JAMA) in 2003. Next, he tested the possibility that brain overgrowth might result from an abnormal excess of brain cells. In November 2011, his study, also published in JAMA, discovered a 67 percent excess of brain cells in a major region of the brain, the prefrontal cortex – a part of the brain associated with social, communication and cognitive development.
“Our next step was to see whether there might be abnormalities of genetic functioning in that same region that might give us insight into why there are too many cells and why that specific region does not develop normally in autism,” said Courchesne.
In the new study, the researchers looked towards genes for answers, and showed that genetic mechanisms that normally regulate the number of cortical neurons are abnormal. “The genes that control the number of brain cells did not have the normal functional expression, and the level of gene expression that governs the pattern of neural organization across the prefrontal cortex is turned down. There are abnormal numbers and patterns of brain cells, and subsequently the pattern is disturbed,” Courchesne said. “This probably leads to too many brain cells in some locations, such as prefrontal cortex, but perhaps too few in other regions of cortex as well.”
In addition, the scientists discovered a turning down of the genetic mechanisms responsible for detecting DNA defects and correcting or removing affected cells during periods of rapid prenatal development.