A family of genes located in a largely hidden part of the human genome may be associated with autism symptom severity, according to scientists at the University of Colorado (CU) Anschutz Medical Campus.
The findings, published in the American Journal of Psychiatry, could lead to new insights into autism spectrum disorder (ASD) and eventually lead to clinical therapies for individuals with the condition.
The researchers discovered that the critical genes, known as the Olduvai family, are in a part of the human genome that is so complex and difficult to study that it has gone without investigation by conventional genome analysis methods.
The researchers, led by James Sikela, Ph.D., a professor in the department of biochemistry and molecular genetics at the CU School of Medicine, analyzed the genomes of people with autism and found that, as the number of copies of Olduvai increased, the severity of autism symptoms became worse.
While the Sikela lab has shown this same trend previously, the finding has not been investigated by other researchers due to the complexity of the Olduvai family.
“It took us several years to develop accurate methods for studying these sequences, so we fully understand why other groups have not joined in.” Sikela said. “We hope that by showing that the link with autism severity holds up in three independent studies, we will prompt other autism researchers to examine this complex family.”
In order to provide more evidence that the Olduvai-autism link is real, the research team used an independent population and developed a different, higher resolution measurement technique. This new method also allowed them to pinpoint which members of the large Olduvai family may be driving the association.
Though autism is believed to have a strong genetic component, conventional genetic studies have come up short in efforts to explain this contribution, Sikela said.
“The current study adds further support to the possibility that this lack of success may be because the key contributors to autism involve difficult-to-measure, highly duplicated and highly variable sequences, such as those encoding the Olduvai family, and, as a result, have never been directly measured in other studies of autism,” Sikela said.