Focal patches of cortical layer disruption – did we solve the mystery of autism?

iStock_000016507590XSmallScientists from the University of California, San Diego Health Sciences and Allen Institute for Brain Science discovered that six layered structure of cortex is focally disrupted in autistic patients. Their results suggest that autism begins long before birth whereas environmental factors influence further disease development.

Autism is a neurodevelopmental disorder characterized by impairment of social interactions, communication difficulties and stereotyped patterns of behavior. According to Centers for Disease Control and Prevention (CDC) about 1 in 50 children has been identified with autism spectrum disorder (ASD) in 2013. Although the complex etiology of autism has been intensively investigated, researchers have not yet identified a single trigger that causes disease development.

The article published in the New England Journal of Medicine is an another attempt to solve the mystery of autism origin. Scientists from the University of California, San Diego School of Medicine and the Allen Institute for Brain Science in Seattle investigated cytoarchitectural changes within the cortex in autistic patients. Examined material constituted neuronal tissue obtained postmortem from children with and without autism between the ages of 2 and 15 years. RNA in situ hybridization with a panel of molecular markers specific for cortical layers was used to phenotype cortical microstructure. Researchers assessed markers for nervous tissue, along with genes that have been related to increased risk of autism.

According to previous studies ASD are associated with neuropathological changes as for e.g. cerebellar hemisphere hypertrophy, hypoplasia of the vermis cerebelli, disorganized cytoarchitecture of a cortex as well as abnormal structure of frontal and temporal lobe and hippocampus. Furthermore it has been proved that neuroanatomical changes accompany impaired synaptic transmission. Cortex of autistic patients is thicker with irregular layers structure and indistinct line between white and gray matter. Ectopic gray matter and elevated neurons number has been also described in some studies. Although many studies conducted, anatomopathological changes in a brain tissue of autistic patients have not been fully elucidated yet.

Data published the New England Journal of Medicine show lack of some molecular markers significant for particular cortex layers in the majority of investigated brain tissue samples (91%) in autistic patients and in 9% in control group. Cortical disorganization of brain tissue were observed as focal patches (5-7mm in diameter) in the area of abnormal laminar six layers cortex cytoarchitecture. Those patches were predominantly localized in frontal and temporal cortex – brainregiones responsible for social behaviors, languages abilities and emotions. Due to focal character of cortex deodorization, it might be possible to induce neuronal connections bypassing this abnormal structures as authors suggest.

Better understanding a focal character of brain tissue disorganization in patients suffering from autism might contribute to extend the knowledge regarding this disease or to create novel therapeutic options.

Written by: Agnieszka Szymczyk, Justyna Markowicz, Tomasz Roman

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