Researchers working to unlock the mysteries of autism report they have discovered differences among children when two in a family have the condition versus just one.
Scientists from Cold Spring Harbor Laboratory in New York have been researching the genetic origins of autism for two decades. Their discoveries have included thousands of genes that, when damaged, may cause a child to be born with an autism spectrum disorder.
They still couldn't account for all cases, so they analyzed the genomes of more than 6,000 volunteer families.
The researchers discovered that in families that have two or more children with autism, the siblings shared more of their father's genome -- the complete set of DNA.
Conversely, in families where only one sibling had autism, the children shared less of their father's genome.
It's not clear how the father's genome has this impact.
Scientists had previously thought that siblings with autism shared more of their mother's genome than their father's.
One theory now is that some fathers may carry protective mutations that fail to get passed on.
It's also possible that fathers may pass down mutations that trigger the mother's immune system to attack the developing embryo, said co-author Ivan Iossifov, an associate professor at Cold Spring.
These theories may offer some hope for parents of children with autism and other neurological disorders like schizophrenia.
"Our future research is exciting," Iossifov said in a laboratory news release. "If one of those theories or two of them prove to be true, then it opens different treatment strategies, which can, in the future, affect quite a lot of families."
The research may also make it possible to better understand autism and to diagnose it earlier, the researchers said.
Autism spectrum disorder varies widely in severity and covers a range of neurological and developmental conditions. About 1 in 36 children in the United States has an autism spectrum disorder, which can affect communication, socialization, learning and behavior.
"There are children diagnosed with autism who are high-functioning," Iossifov said. "They have a completely productive life, although they have some minor troubles in social interactions, as most of us do. But also, there are children diagnosed with autism who never learn to speak, and they have definitely a difficult life."
The research was published recently in Cell Genomics.