The study, conduced by researchers affiliated with the UC Davis MIND Institute, also offers a potential target for drugs to treat the condition.
Previous studies have already demonstrated that the gene is defective in children with autism, but were unable to determine its effects on neurons on the brain. In this study, the team found that in mice, the gene disrupted energy use in neurons. They found that these damaging effects were associated with antisocial and prolonged repetitive behavior - characteristics of autism.
Cecilia Giulivi, Professor of molecular biosciences in the UC Davis School of Veterinary Medicine and a researcher affiliated with the UC David MIND Institute, explained:
"A number of genes and environmental factors have been shown to be involved in autism, but this study points to a mechanism - how one gene defect may trigger this type of neurological behavior. Once you understand the mechanism, that opens the way for developing drugs to treat the condition.
The defective gene appears to disrupt neurons' use of energy, the critical process that relies on the cell's molecular energy factories called mitochondria."
For the study, the researchers tweaked a gene called pten in mice so that neurons were deficient in the normal amount of pten's protein. Four to six weeks after birth, the team discovered malfunctioning mitochondria in the mice.
By weeks 20-29, the team found that DNA damage in the mitochondria and disruption of their function had increased significantly. Around this time, the mice began engaging in repetitive grooming behavior and avoided contact with the other mice.
Giulivi explained: "The antisocial behavior was most pronounced in the mice at an age comparable in humans to the early teenage years, when schizophrenia and other behavioral disorders become most apparent."
According to the researchers, when pten proteins are defective, they interact with the protein of a second gene (p53) to reduce how much energy is produced in neurons. This causes an increase in harmful mitochondria DNA changes and abnormal levels of energy production in the cerebellum and hippocampus, areas of the brain vital for cognition and social behavior.
Mutations in pten proteins have also been associated with Alzheimer's disease and a spectrum of autism disorders. According to the researchers, when pten protein was lacking, its interaction with p53 activated deficiencies and defects in other proteins that have been identified in individuals with learning disabilities, such as autism.
The study was funded by the Autism Speaks Foundation, the MIND Institute, the Elsa U. Pardee Foundation and the National Institute of Environmental Health Sciences.
Written by Grace Rattue