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Autism researchers have uncovered a clue to the mystery of why autism affects four times as many boys as girls: a genetic glitch that only affects boys.

A team of international researchers led by Professor Stephen Scherer, Senior Scientist and Director of the University of Toronto’s McLaughlin Centre and The Centre for Applied Genomics at The Hospital for Sick Children (SickKids), published the findings in the online edition of The American Journal of Human Genetics.

Dr. Scherer holds the GlaxoSmithKline-CIHR Pathfinder Chair in Genetics and Genomics at the University of Toronto and SickKids. Dr. Peter Szatmari at the Offord Centre for Child Studies at McMaster University is the co-author of the study.

The researchers analyzed the genes of more than 1,600 people with Autism Spectrum Disorder (ASD). The analysis pointed to an alteration in the SHANK1 gene.  The SHANK gene family is coded for proteins involved in the formation and function of neural synapses in the brain.

SHANK2 and SHANK3 genes have previously been linked to ASD and intellectual disability.

Researchers identified six people from the same family who carried the SHANK1 mutation. The most significant finding was that only the four males with the genetic change had ASD, while the female carriers did not. Another male from a different family also had a SHANK1 mutation and ASD.

“Now we have more insight as to why males could be more susceptible to ASD than females,” Scherer said. “This study indicates that there may be a protective factor preventing these female carriers from developing ASD.”

If researchers can determine why SHANK1 females are being protected from ASD, then this “protective factor may one day be used to prevent or treat the disorder,” said Scherer.

The research was supported by grants from the University of Toronto McLaughlin Centre, NeuroDevNet, Genome Canada/Ontario Genomics Institute, the Canadian Institutes of Health Research (CIHR), the Canadian Institute for Advanced Research (CIFAR), the Canada Foundation for Innovation, the Ontario Ministry of Economic Development and Innovation, Autism Speaks and SickKids Foundation.