Popular belief holds that siblings who inherit autism possess the same risk genes for the disorder as their parents and each other. But a shocking new study – deemed the largest ever autism genome study to date – finds this may not be the case.
While the exact causes of autism are uncertain, researchers have associated a number of genes with the disorder, many of which are believed to be inherited.
A new study found that nearly 70% of the studied siblings had different risk genes for the condition. The study, published in the journal Nature Medicine and led by Dr. Stephen Scherer of The Hospital for Sick Children in Ontario, Canada, questions whether autism is typically inherited or a result of other things.
Autism affects about 1 in 68 children in the US and is almost five times more frequent among boys than girls.
Numerous studies have suggested that autism can be inherited. According to the Centers for Disease Control and Prevention (CDC), research has shown us that if one identical twin has autism, the other twin has a 36-95% chance of developing the condition.
Studies have also shown that parents who have a child with autism have a 2-18% chance of having another child with the condition. Each child with autism is like a snowflake – unique from each other.
For their study, Dr. Scherer and his team conducted whole genome sequencing on 85 families with two siblings who had been diagnosed with autism. Instead of standard genetic testing, whole genome sequencing assesses the entire DNA make-up of an organism’s genome at one time.
The results of the analysis discovered that 69.4% of siblings carried different autism-related genetic mutations. The researchers also found that these siblings displayed more variability in autism symptoms than the 30.6% of siblings who did share the same autism-risk genes.
These findings signify that among siblings who both have autism, the disorder may be caused by gene mutations that have “developed sporadically.”
Medical News Today asked Dr. Scherer if these findings came as a surprise. “Initially this surprised us,” he replied, “but when we thought more about it, based on what we know, it seems to make sense. Lots of different genes are involved [in autism] – more than 100 – and based on all of the different potential combinations of events; it would be more likely for different genes to be involved than the same gene. We knew that there were many differences in autism, but our recent findings firmly confirm that. We believe that each child with autism is like a snowflake – unique from the other.”
Dr. Scherer says the findings also suggest clinicians should go beyond searching for suspected autism-related genes, as is normally done using diagnostic genetic testing. He adds, “What often happens now is that if there is an older child with an autism diagnosis and the gene involved is known, in future children – for reasons of genetic counseling – they often just sequence the known gene to look for mutations in the siblings or other family members,” he told us. “Our story shows you need to go deeper than that and preferably sequence the entire genome.”
The data in this study form a part of the MSSNG project – a collaboration between Autism Speaks, who funded the study, and Google. The project’s goal is to produce a database of at least 10,000 autism genomes openly available for global research, with the aim of improving the understanding of autism and aiding the development of personalized treatments for the condition.
Study co-author Robert Ring, chief science officer at Autism Speaks, says making such data accessible to researchers worldwide is “breaking down barriers in a way never done before.”
“As always, our goal at Autism Speaks is to accelerate scientific discovery that will ultimately improve the lives of individuals with autism at home and around the world,” he adds.
Author: Blaine Pollock
Philanthropist and Businessman, Blaine Pollock is the creative force behind World News MD/Depression.net. Blaine is also the author of the newly released Children’s Book “O My Walter’. Find the magical book, “O My Walter” at www.omywalter.com