A team of researchers has discovered a genetic mutation that causes autism. The team also determined the mechanisms that lead to autism when a patient has this particular mutation. This information was used to treat laboratory mice that were expressing the same gene mutation. The details are in a paper that was just published in the journal Cell.
Autism disorders vary in symptoms and severity but common signs include communication issues, repetitive or obsessive behaviors, and inability to recognize social cues. Autism, which is a developmental disorder, usually manifests in early childhood and many symptoms can be managed with proper treatment and support. The exact cause is unknown although scientists have found genes that seem to contribute to the disorder.
Researchers from the Institute of Science and Technology Austria first identified a mutated version of an important gene called SLC7A5 that was found in children who had later developed autism. SLC7A5 normally helps transport amino acids, the building blocks of proteins. Specifically, SLC7A5 transports branched-chain amino acids to the brain. When the gene is deleted in mice, their neurons fail to synthesize certain proteins correctly. The mice then begin to show early signs of autism, including reduced social behaviors and withdrawal from interactions with other mice. There is a mutation, found in the autistic individuals first studied, that deletes the SLC7A5 gene. This may provide an explanation for some forms of autism.
Since the deletion of SLC7A5 results in a lack of branched-chain amino acid transport to the brain, the research team tried dosing the mice with the missing amino acids. Even though the mice lacked the SLC7A5 gene, the manual addition of the amino acids was enough to significantly reduce symptoms of autism. This method required adding the amino acids directly to the brains of the mice. The treatment would unfortunately be impractical for human patients.
The team’s findings show a new cause of certain types of autism. The authors are quick to note that this only applies to specific types of the disorder. The good news is that the changes caused by the gene mutation were reversible and the mice improved after treatment. The team hopes that their study will help scientists better understand the disorder.
Tărlungeanu et al. Impaired Amino Acid Transport at the Blood Brain Barrier Is a Cause of Autism Spectrum Disorder. Cell (2016).