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Canadian doctors out of the University of Toronto say the scarcity of a single protein in the brain may be what’s to blame for up to a third of autism cases.

The brain protein in question is called nSR100 – also known as SRRM4 – and it’s pivotal for normal brain development. The latest findings build on the researchers’ work on how decreased levels of the protein are tied to autism.

“We previously reported an association between nSR100 protein levels and autism. But this time we show that reduced levels of this protein could really be causative – that’s a big deal. Just by reducing the nSR100 levels by 50 per cent, we observe hallmarks of autistic behaviour,” said Dr. Sabine Cordes of the university’s Department of Molecular Genetics. Tweet This

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The team is calling their findings a “breakthrough” in understanding autism spectrum disorder, a neurological disorder the medical community is still trying to understand.

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Autism spectrum disorder (ASD) includes a group of complex disorders of brain development, according to Autism Speaks Canada. In May 2013, the DSM-5 – dubbed the mental health bible for health care professionals – merged autism disorders into one umbrella diagnosis of ASD.

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Researchers still don’t know what causes autism, but they’re focusing their efforts on genetics.

In the U of T research, for example, scientists learned nSR100 was “diminished” in the brains of many people with autism. They learned this in post-mortem studies on people with autism – in many of the cases, doctors couldn’t figure out why these people had the disorder.

In their latest study, the team wanted to know if a scarcity causes autism, too – they created mice that lack the protein to study their behaviour.

The protein plays a major role in the brain. Without nSR100, mice die. Turns out, taking away 50 per cent of the protein triggered “hallmark” autistic behaviour.

READ MORE: Autism, even in siblings, has different genetic causes, Canadian study suggests

The mice were highly sensitive to noise and avoided social interaction, preferring to play alone when they were grouped with peers. Inside the brain, other features were present too, from splicing proteins to different wiring.

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The scientists hope their findings can help to explain some autism cases. It could even offer a treatment option by reversing nSR100 deficiency in humans.

“In the future, if you turned this protein up a little bit in autistic patients, you might be able to improve some of the behavioural deficits,” Cordes said.

The team’s full findings were published Thursday in the journal Molecular Cell.

READ MORE: Scientists find more genes possibly linked to autism with advanced sequencing tool

One in 68 children fall under the autism spectrum disorder, according to the Centers for Disease Control and Prevention.

Health Canada points to global statistics – “an average prevalence” of about one per cent – but it’s working on a national surveillance system for autism that won’t be ready until the New Year.

Right now, there are no blood or biological tests for autism. It’s diagnosed by making judgments about a child’s behaviour.

carmen.chai@globalnews.ca

Follow @Carmen_Chai