In a new mouse study, University of California, Davis, researchers have found that a defective gene is responsible for brain changes that lead to the disrupted social behavior that accompanies autism.
Investigators believe the discovery could lead to the development of medications to treat the condition.
Prior research had determined that the gene is defective in children with autism, but its effect on neurons in the brain was not known.
The new studies in mice show that abnormal action of just this one gene disrupted energy use in neurons. The harmful changes were coupled with antisocial and prolonged repetitive behavior — traits found in autism.
The research is published in the scientific journal PLoS ONE.
“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,” said study senior author Cecilia Giulivi, Ph.D.
“Once you understand the mechanism, that opens the way for developing drugs to treat the condition,” she said.
The defective gene appears to disrupt neurons’ use of energy, Giulivi said, the critical process that relies on the cell’s molecular energy factories called mitochondria.
In the research, a gene called pten was modififed in the mice so that neurons lacked the normal amount of pten’s protein. The scientists detected malfunctioning mitochondria in the mice as early as 4 to 6 weeks after birth.
By 20 to 29 weeks, DNA damage in the mitochondria and disruption of their function had increased dramatically.
At this time, the mice began to avoid contact with their litter mates and engage in repetitive grooming behavior. Mice without the single gene change exhibited neither the mitochondria malfunctions nor the behavioral problems.
The antisocial behavior was most pronounced in the mice at an age comparable in humans to the early teenage years – a period in which schizophrenia and other behavioral disorders become most apparent, Giulivi said.
The research showed that, when defective, pten’s protein interacts with the protein of a second gene known as p53 to dampen energy production in neurons.
The interaction causes severe stress that leads to a spike in harmful mitochondrial DNA changes and abnormal levels of energy production in the cerebellum and hippocampus — brain regions critical for social behavior and cognition.
Investigators report that pten mutations previously have been linked to Alzheimer’s disease as well as a spectrum of autism disorders.
The new research shows that when pten protein was insufficient, its interaction with p53 triggered deficiencies and defects in other proteins that also have been found in patients with learning disabilities including autism.