Dec. 23 (UPI) -- A child's risk for developing autism spectrum disorder may be linked to genetic mutations found only in the father's sperm, a new study has indicated.
In an article published Monday in the journal Nature Medicine, researchers noted they have developed a method for measuring the presence of these disease-causing mutations in male sperm.
They believe their approach could provide expectant parents and their physicians with a more accurate assessment of autism risk.
"With our new study, we can trace some of these mutations back to the father, and we can directly assess the risk of these same mutations occurring again in future children," co-author Jonathan Sebat, chief of the Beyster Center for Molecular Genomics of Neuropsychiatric Diseases at the University of California-San Diego School of Medicine, said in a press release.
Autism spectrum disorder affects nearly 2 percent of all children in the United States. Its causes are not fully understood, although researchers believe both genetics and environment play a role.
Previous studies have suggested that, in as many as 30 percent of cases, the disorder is linked to genetic mutations that appear only in the child and are not inherited from either parent's DNA.
It is believed that the number of gene-damaging mutations -- which occur spontaneously in parents' sperm or eggs or during fertilization and are present in each cell as the fertilized egg divides -- rise with the father's age at time of conception, and the chance of the mutation recurring within the same family is estimated at 1 to 3 percent.
"However, such estimates are not based on actual knowledge of the risk in an individual family, but instead are based on frequencies in the general population," said co-author Dr. Joseph Gleeson, Rady director of neuroscience research at the Rady Children's Institute for Genomic Medicine.
"When a disease-causing mutation occurs for the first time in a family, the probability that it could happen again in future offspring is not known. Thus families must make a decision with a great deal of uncertainty."
To find a way to mitigate some of that uncertainty, Gleeson, Sebat and their colleagues decided to analyze the sperm of eight fathers who were parents of children with autism spectrum disorder.
Using deep whole genome sequencing, they looked for the presence of multiple, genetically different material in cells in the same person -- a phenomenon called mosaicism -- found variants in offspring that were matched only in the fathers' sperm.
They also noted that disease-causing mutations were present in up to 15 percent of the fathers' sperm cells -- information that could not be determined through other means, such as blood tests. The researchers said fathers could have their sperm studied to determine the risk of recurrence of these mutations in their children.
The test also could be used in men who haven't had children, but who want to know the risk of having a child with autism, the researchers said.
"My laboratory ... previously showed that mosaicism in a child can lead to diseases like epilepsy," Glesson said. "Here, we show that mosaicism in one of parents is at least as important when thinking about genetic counseling."