THURSDAY, Aug. 29 (HealthDay News) -- A group of enzymes in the
brain appears to be key to the activity of many genes linked to
autism, a new study reveals.
Experts hope the findings will shed light on the causes of
autism, and possibly lead to new treatments.
The study results, published online Aug. 28 in the journal
Nature, hint that if disruptions in enzymes called
topoisomerases occur during brain development, they might
contribute to the development of autism spectrum disorders.
The enzymes are found throughout the body, and their main job is
to "untangle the knots" in cells' DNA so the cells can function and
reproduce themselves normally, explained senior researcher Mark
Zylka, an associate professor of cell biology at the University of
North Carolina at Chapel Hill.
Topoisomerases have been well studied for their role in helping
tumor cells to spread, and drugs that inhibit the enzymes are
already used to treat certain cancers.
There have also been hints, though, that topoisomerases might
contribute to autism. Last year, researchers reported that some
people with autism spectrum disorders have mutations in these
"But we've known little about how they work in the brain," said Zylka.
In lab experiments with mouse and human brain cells, Zylka's
team found that a topoisomerase-inhibiting drug reduced the
activity of 49 genes that past studies have linked to autism. That
points to the importance of topoisomerases in the normal expression
of those genes.
"A single drug down-regulated all of those genes," Zylka said.
That does not mean, however, that topoisomerase inhibitors
should be tested for treating autism. If anything, Zylka explained,
you would want a drug that enhances the enzymes' actions.
But now researchers can look for compounds that do just
What's more, the findings point to a biological process that
ties together dozens of different genes that are suspected of being
involved in autism. "Well over 300 (autism-linked) genes have been
identified now," Zylka said. "That list looks daunting, but the
goal is to figure out how all these genes are connected," he
"It can be overwhelming when you look at the list of genes," agreed Andy Shih, senior vice president for scientific affairs for the advocacy group Autism Speaks.
But if you can zero in on the "biological pathways" linking
those genes, "it all starts to make sense," said Shih, who was not
involved in the study.
In the United States, it's estimated that at least one in every
88 children has an autism spectrum disorder, with the severity
ranging widely from child to child. Some kids have little or no
ability to speak, and focus obsessively on just a few interests;
other kids speak and have normal to above-normal intelligence, but
may have problems socializing and communicating more subtly -- for
example, trouble using and "reading" gestures, body language and
No one knows what causes autism spectrum disorders, but experts
believe that it's a complex mix of genetic vulnerability and
environmental exposures -- possibly chemicals or microbes.
Shih pointed to an "interesting" fact about topoisomerases:
Their activity is believed to be influenced by environment,
including compounds in food and in the physical world. So, he said,
studying the enzymes might help researchers pinpoint some of the
environmental factors that contribute to autism spectrum
"We've been talking for a long time about the interaction between genes and environment in autism," Shih said. Topoisomerases could offer a way for scientists to begin to connect the dots.
Zylka agreed, and said his team is searching for environmental
compounds that inhibit topoisomerases -- and may, therefore, be
important for pregnant women or young children to avoid.
There is still, however, a long way to go in fully understanding
the underpinnings of autism spectrum disorders. "We've just
scratched the surface of what's going wrong in the brain" in
autism, Zylka said.
The U.S. Department of Health and Human Services has more on
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