Autism researchers can no longer rely on rudimentary genetic testing to check for a child’s gene-risks for autism, according to the largest-ever study of human genomes. Instead, the new data show they must rely on individualized testing for each person’s genome in order to develop effective treatment options.

Funded by Autism Speaks, the study combed through 340 whole genomes from 85 families, who each had two children with autism spectrum disorder (ASD). It found a striking number of differences between siblings, despite both falling somewhere on the spectrum. In fact, the majority of siblings (69 percent) shared no specific genes known to be related to autism. Scientists behind the research suspect the results mean even more work is ahead of them in understanding the complex disorder.

"We knew that there were many differences in autism, but our recent findings firmly nail that down," said the study’s principal investigator and leader of Autism Speaks' MSSNG program, Dr. Stephen Scherer, said in a statement. "We believe that each child with autism is like a snowflake — unique from the other."

In addition to scanning hundreds of genomes, all the data the team uncovered has been made freely available as part of 1,000 autism genomes on the MSSNG portal in the Google Cloud Platform. Worldwide, autism researchers will be able to use the information in their own future studies, which Scherer and his colleagues hope will accelerate the progress that has already been made.

"This is an exemplar for a future when open-access genomics will lead to personalized treatments for many developmental and medical disorders," said Scherer, emphasizing the counter-intuitive point that familial autism risks don’t guarantee children will necessarily share certain genes.

Prevalence of ASD in the U.S. is increasing. In the year 2000, roughly one in 150 kids was diagnosed. In 2010, the rate had jumped to one in 68, tipping predominantly toward boys. While part of that rise is due to better diagnostic tools, experts suspect other factors are at play, namely, a mix of environmental and genetic influences that lead to abnormal fetal brain development.

Scherer’s study did uphold some things scientists already knew. For instance, they found 42 percent of families showed autism-risk genes, reflecting the genetic link between generations. Differences arose, however, in which genes cropped up in their analysis. "This may help explain why autism came about in their child or provide insight into related medical conditions," he said.

The research is early, if promising. Ultimately, Autism Speaks hopes to make at least 10,000 autism genomes available for research, along with a numerous tools for data analysis. And with the unprecedented cloud capabilities, says Robert Ring, study co-author and chief science officer at Autism Speaks, "we're breaking down barriers in a way never done before."

Source: Yuen R, Thiruvahindrapuram B, Merico D, et al. Whole-genome sequencing of quartet families with autism spectrum disorder. Nature Medicine. 2015.