Numerous studies have tried to understand the genetic component of autism in an effort to understand the origins of the disorder. A few key genes have come up as important including a gene known as CHD8 or Chromodomain-helicase-DNA-binding protein 8. This gene has been shown to be mutated in some individuals with autism and be associated with enlarged brains and mild to severe intellectual disabilities. CHD8 is important in packing a cells DNA into more compact structures called chromatin. Chromatin allows the cell to control which genes are expressed, prevent damage to the DNA, and control when the DNA is copied for cell division. Up to this point we had little knowledge on how CHD8 mutations could impact brain development and lead to autism in some individuals. This is where a team of researchers from the University of California stepped in.
The team took normal mice embryos and mutated their CHD8 in the same location as identified in humans and tracked the development of the mice and their brains. The team saw that the mice with the mutated CHD8 had impaired cognitive ability and had larger brain volumes than their non-mutant cousins. This enlargement of the brain was due to excessive growth and division of the neurons in the mouse brain. The finding correlates nicely with autism where an enlarged brain (megaencephaly) is common in some people. Interestingly, the defective CHD8 continued to function throughout the mouse’s lifespan contributing to defects in neuronal connections and synapses. This suggests that CHD8 may control many functions in the developing brain and underpin much of the abnormal development that occurs in autism.
While these results are exciting we don’t yet know if the same processes are occurring in the developing human brain. Additionally, CHD8 mutations are not found in every person with autism or autism spectrum disorder and so this insight may not be generalizable to all people with the disorder. The study does however further our understanding of how the brain develops normally and what happens when it is disrupted. In the future it should be possible to target processes involved in brain development early in life to stunt the progression of autism.
Image Credit: The Blue Diamond Gallery