Potential Autism Trigger Found in Brain Growth Enzymes

Some cases of autism may be related to damage in a key set of enzymes that are critical during brain growth and development, possibly helping narrow the search for causes of the condition, researchers said.

The enzymes known as topoisomerases work like scissors and glue when brain cells known as neurons are being copied or expressed, said Mark Zylka, an associate professor in the Neuroscience Center at the University of North Carolina School of Medicine in Chapel Hill. When studies linked mutations in the enzymes to some patients with autism last year, the researchers sought to determine what exact effect they had on the brain.

The study found the enzymes are essential for the proper functioning of some extremely long genes, including dozens of those that have gone awry in patients with autism, Zylka said. The researchers inhibited the enzymes with a generic cancer medicine and found they effectively silenced about 50 genes linked to autism, according to the study published today in the journal Nature.

“Our study shows the magnitude of what can happen if topoisomerases are impaired,” Zylka said. “We think there are probably other drugs or chemicals in the environment that can have this same effect. We believe this is just the tip of the iceberg. We are doing additional research to see if other compounds like this exist, and we have hints there are others.”

One in 50 U.S. children are diagnosed with autism or a related disorder, according to the Centers for Disease Control and Prevention. Children with autism may be unresponsive to people, become indifferent to social activity and have communication difficulties.

The findings should help investigators in their hunt for causes of autism, Zylka said. While in the past scientists had no idea what to look for, now they can quickly zero in on compounds that inhibit topoisomerases.

“We can now systematically screen drugs for similar effects on autism genes,” he said, explaining that other compounds and chemicals may also cause damage. “That’s a real future direction that has the potential to identify environmental causes of autism.”

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