Brothers SmilingDo siblings with autism spectrum disorder (ASD) share the same genes? They do, but not as often as you might expect. A new study conducted by Autism Speaks analyzed fully-sequenced genomes from families affected by ASD. The results showed that around two-thirds of sibling pairs with ASD have different autism-related genes. The study, which is the largest autism genome study to date, calls into question typical methods for investigating the genetics of ASD.

The researchers sequenced 340 complete genomes from the members of 85 families. Each family had two children affected by ASD. The genomes were selected from a bank of approximately 1,000 ASD genomes in the Autism Speaks MSSNG cloud platform.

The majority of sibling pairs did not share the same genetic markers of ASD. In fact, 69 percent of siblings had little to no genetic overlap in gene variations known to be associated with autism spectrum disorders. Only 31 percent of sibling pairs shared the same autism-related genetic pairs.

It has long been suspected that siblings with ASD share the same genetic markers because ASD runs in families. However, the study challenges the presumption that siblings inherit the same genes that predispose them to ASD.

Dr. Stephen Scherer, head of the MSSNG program and director of the Center for Applied Genomics at Toronto’s Hospital for Sick Children, explains the study’s impact on genetic testing for ASD. “This means we should not be looking just for suspected autism-risk genes, as is typically done in diagnostic genetic testing. A full assessment of each individual’s genome is needed to determine how to best use knowledge of genetic factors in personalized autism treatment.”

This research is published in Nature Medicine.

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