A genetic mutation causes mice to over-groom to the point of near baldness, except for an obsessively touched-up strip of hair between the ears.
Such were the findings of an international team of neuroscientists at NYU Langone Medical Center, who intentionally bred the mice hoping to uncover clues about autism.
Over-grooming, a repetitive motor behavior, has long been associated with autism in mice. In humans, the disease can manifest itself in similarly dysfunctional behaviors such as repeated actions and lack of empathy.
But this experiment is the first in which a specific autistic motor behavior has been identified as the result of a process referred to in the science community as a biological pathway.
If the effects of this genetically determined pathway are reversible, says senior study investigator Gordon Fishell, PhD, the Julius Raynes Professor of Neuroscience and Physiology at NYU Langone, new treatments for autism could soon be available.
The mice were operating on reduced production of a protein called Cntnap4, the effects of which overstimulate the production of dopamine and block the chemical signals of GABA short for gamma-aminobutyric acid.
Both neurotransmitters, dopamine stimulates the hormones to produce pleasant sensations, while GABA is responsible for controlling brain impulses.
Too much of the former and not enough of the latter can lead to repetitive motor behaviours, otherwise known as classic autism symptoms.
"Our study tells us that to design better tools for treating a disease like autism, you have to get to the underlying genetic roots of its dysfunctional behaviors, whether it is overgrooming in mice or repetitive motor behaviors in humans," said Dr. Fishell in a statement released through Newswise. "There have been many candidate genes implicated in contributing to autism, but animal and human studies to identify their action have so far not led to any therapies. Our research suggests that reversing the disease's effects in signaling pathways like GABA and dopamine are potential treatment options."
The mice who preened the most -- by nature, mice groom each other -- had reached maturity, which inspired Dr. Fishell and his team to plan more studies based on changes in dopamine production and GABA messaging in adult brain cells.
Tracing the steps of what makes a biological pathway gone awry in the first place could lead to the discovery of a solution to put it back on track.
Genome research aiming to crack the autism code has been plentiful and puzzling. Individuals exhibiting symptoms often have unaffected siblings with the same genetic mutations.
In light of another recent study, Fishell's work indicates that biological pathways gone awry could be the main cause of autism rather than genetic mutations alone.
Stephen Scherer, director of Toronto's Hospital for Sick Children's Centre for Applied Genomics, led a team to discover a formula predicting which genetic mutations are likely to result in autism, flagging 3,955 exons in 1,744 genes.
According to the CDC, Autism Spectrum Disorder is five times more common in boys than in girls and affects about one in 68 children.
Dr. Fishell's study is to be published in the journal Nature.
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