Posts Tagged Autism

Gene Related to Autism Behavior ID’d in Mice Study


Gene Related to Autism Behavior ID'd in Mice StudyIn 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.

Source: University of California – Davis Health System

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Mice Study Shows Overactive Immune System Contributes to Autism


Mice Study Shows Overactive Immune System Contributes to Autism  A new study suggests that changes in an overactive immune system can contribute to autism-like behaviors in mice.

The study from the California Institute of Technology (Caltech) also found that, in some cases, this activation can be related to what a developing fetus experiences in the womb.

“We have long suspected that the immune system plays a role in the development of autism spectrum disorder,” said Dr. Paul Patterson, the Anne P. and Benjamin F. Biaggini Professor of Biological Sciences at Caltech, who led the work.

“In our studies of a mouse model based on an environmental risk factor for autism, we find that the immune system of the mother is a key factor in the eventual abnormal behaviors in the offspring.”

The first step was establishing a mouse model that tied the autism-related behaviors to immune changes, he said.

Several large studies — including one that involved tracking the medical history of every person born in Denmark between 1980 and 2005 — found a correlation between viral infection during the first trimester of a mother’s pregnancy and a higher risk for autism in her child. As part of the new study, researchers injected pregnant mouse mothers with a viral mimic that triggered the same type of immune response a viral infection would.

“In mice, this single insult to the mother translates into autism-related behavioral abnormalities and neuropathologies in the offspring,” said Elaine Hsiao, a graduate student in Patterson’s lab and lead author of the paper.

The team found that the offspring exhibit the core behavioral symptoms associated with autism spectrum disorder, including repetitive or stereotyped behaviors, decreased social interactions, and impaired communication.

In mice, this translates to such behaviors as compulsively burying marbles placed in their cage, excessively self-grooming, choosing to spend time alone or with a toy rather than interacting with a new mouse, or vocalizing ultrasonically less often or in an altered way compared to typical mice.

Next, the researchers studied the immune system of the offspring of mothers that had been infected and found that they displayed a number of immune changes.

Some of those changes parallel those seen in people with autism, including decreased levels of regulatory T cells, which play a role in suppressing the immune response, the researchers said.

Taken together, the observed alterations add up to an immune system in overdrive, which promotes inflammation.

“Remarkably, we saw these immune abnormalities in both young and adult offspring of immune-activated mothers,” Hsiao said. “This tells us that a prenatal challenge can result in long-term consequences for health and development.”

The researchers were then able to test whether the offspring’s immune problems contribute to their autism-related behaviors. In a test of this hypothesis, the researchers gave the affected mice a bone-marrow transplant from typical mice.

The normal stem cells in the transplanted bone marrow not only replenished the immune system of the mice, but altered their autism-like behavior, the researchers report.

The researchers note that because the work was conducted in mice, the results cannot be readily extrapolated to humans, and they do not suggest that bone-marrow transplants should be considered as a treatment for autism.

They also have yet to establish whether it was the infusion of stem cells or the bone-marrow transplant procedure itself — complete with irradiation — that corrected the behaviors.

However, the results do suggest that immune irregularities in children could be an important target for innovative immune manipulations in addressing the behaviors associated with autism, said Patterson. By correcting these immune problems, it might be possible to ameliorate some of the classic developmental delays seen in autism, he noted.

The results appear in a paper in the Proceedings of the National Academy of Sciences (PNAS).

Source: California Institute of Technology

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