Common genetic variants identify autism risk in high risk siblings of children with ASD

By focusing on the identification of common genetic variants, researchers have identified 57 single nucleotide polymorphisms (SNPs) that predict - with a high degree of certainty - the risk that siblings of children with Autism Spectrum Disorder (ASD) will also develop the condition. The findings were presented at the International Meeting for Autism Research.

ASD is among the most common form of severe developmental disability with prevalence rates up to 1 in 88 children. Boys are greater than four times more likely to be diagnosed with ASD, while recurrence risks for the sibling of a child with ASD are estimated at 18.7%. Since multiple studies have shown that early assessment and intervention offer significantly improved long-term outcomes, early identification of children at risk of ASD has become a key goal.

Though many recent studies demonstrate that autism has a genetic basis, the inheritance pattern of ASD in most families is highly complex. While genetic testing for autism has been limited to the identification of copy number variants (CNVs), autism-associated CNVs are found only in approximately 10% of children with ASD.

Researchers seeking an alternative approach to identify biomarkers for autism have focused on a number of common genetic variants -or SNPs -that have been shown to be related to the risk of ASD. While individual SNPs do not cause ASD, recent studies have shown that the presence of a combination of autism-associated SNPs can predict with a high degree of certainty whether a child will develop ASD.

"By looking at a combination of gender-specific, risk-associated, genetic common variants, we were able to identify siblings of children with ASD who have a significantly increased risk of developing autism," says lead author Francois Liebaert, MD, Vice President of Research and Development for IntegraGen, SA, Evry, France, "Earlier identification of siblings of children with autism at increased risk may lead to faster referrals, earlier diagnosis, earlier intervention and better prognosis. We also hope to replicate these findings in families that do not have a child with autism."

These findings build upon earlier identification of eight autism-related SNPs that occur in males and females (Autism risk assessment in siblings of affected children using sex-specific genetic scores) published the February 17, 2011 edition of Molecular Autism.

To determine which SNPs were associated with autism, researchers applied techniques that have been used to analyze other complex diseases. By combining statistical results from genome wide association studies (GWAS) with biological information from multiple sources including databases and scientific literature, the researchers were able to identify and prioritize the SNPs, and develop gender-specific genetic scores to predict the risk of autism.

What is an autism spectrum disorder? Different people with autism can have very different symptoms. Health care providers think of autism as a "spectrum" disorder, a group of disorders with similar features. One person may have mild symptoms, while another may have serious symptoms. But they both have an autism spectrum disorder.