ATLANTA, Ga. (CBS Atlanta) – A new study has found that autism begins early in pregnancy.
Researchers from the University of California, San Diego School of Medicine and the Allen Institute for Brain Science analyzed 25 genes in the brain tissue of deceased children with and without autism.
They found that the outermost layered structure of neural tissue is disrupted in children with autism by looking at genes that serve as biomarkers for brain cell types in different layers of the cortex as they specifically looked at genes implicated in autism and several control genes.
“Building a baby’s brain during pregnancy involves creating a cortex that contains six layers,” Eric Courchesne, PhD, professor of neurosciences and director of the Autism Center of Excellence at UC San Diego said in a press release. “We discovered focal patches of disrupted development of these cortical layers in the majority of children with autism.”
“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,” Ed S. Lein, PhD, of the Allen Institute for Brain Science in Seattle, explained.
Each cortical layer develops its own specific types of brain cells with specific patterns of brain connectivity that perform unique and important roles in processing information. This happens during early brain development. A distinct genetic signature or “marker” can be observed as a brain cell develops into a specific type in a specific layer with specific connections.
Researchers found that key genetic markers weren’t present in brain cells in multiple layers in the brains of children with autism.
“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.”
Researchers also noted that the early developmental defects were present in focal patches of cortex, which suggests that the defect is not uniform throughout the cortex. They explained that the brain regions most affected by focal patches of absent gene markers were the frontal and temporal cortex, which possibly shows why different functional systems are impacted across individuals with autism.
“The fact that we were able to find these patches is remarkable, given that the cortex is roughly the size of the surface of a basketball, and we only examined pieces of tissue the size of a pencil eraser,” said Lein. “This suggests that these abnormalities are quite pervasive across the surface of the cortex.”
Courchesne added that “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.”
The study will be published in the March 27 online edition of the New England Journal of Medicine.
The Centers for Disease and Control Prevention reported that one in 88 children have been identified with an autism spectrum disorder (ASD). In 2006-2008 about one in six children in the U.S. had a developmental disability ranging from mild disabilities such as speech and language impairments to serious developmental disabilities such as cerebral palsy and autism.