Abnormalities in proteins that help connect neurons produced autism-like symptoms in mice, which may focus the search for drugs to treat people, researchers said.
The genetically altered mice had difficulty communicating, weren’t good at social interaction and showed repetitive behaviors, according to a paper published today in the journal Nature.
Some scientists are studying whether autism is the result of wrongly connected spaces between brain cells. Today’s data bolster that theory because the mutant mice had too many brain connections, making it impossible for the cells to communicate, said Daniel Smith, senior director of discovery neuroscience for Autism Speaks, an advocacy group based in New York.
“The bottom line is it’s still a long way from treating patients, but it’s exactly what we need from early discovery,” Smith, who didn’t participate in today’s study, said in a phone interview. “It gives us something more to hang our hat on.”
The U.S. Centers for Disease Control and Prevention reported in March that 1 in 88 children in the U.S. had autism or a related disorder in 2008, the latest period for which data is available. That was a 23 percent rise from 2006, the agency’s researchers reported, saying it was unclear how much of the increase was due to greater awareness of the disease.
The scientists in today’s study, led by Nahum Sonenberg, of McGill University in Montreal, research how proteins are made to look for clues to cancer. When they knocked out a gene called 4E-BP2, more proteins called neuroligins were produced in the mice.
Brain cells, called neurons, are connected through junctions called synapses. Neuroligins are on the receiving end of a synapse and too many of them increase the number of synapses. That isn’t necessarily good, though, Sonenberg said in a telephone interview.
“Neuroligins make contact, like a handshake,” Sonenberg said. “But with this mutation, the handshake becomes more like a tackle. It’s too much.”
To see if the changes caused by the gene mutation were reversible, the scientists gave the mice an experimental cancer drug to cut some of the synapse formation. After the now-adult mice received the medicine, many of their social deficits attenuated.
The drug isn’t safe for people because it’s too toxic, Sonenberg said. However, its demonstration in mice may spur scientists to explore similar compounds as treatments for the symptoms of autism, he said. Because the pathway has been well-studied in cancer, there may already be treatments available, said co-author Christos Gkogkas, a post-doctoral fellow at McGill.
The study was supported by grants from the Canadian Institutes of Health Research and Autism Speaks, among others.