New studies published in the scientific journal Nature show that genetic mutations in the womb may be the cause of 15% of cases of autism spectrum disorders.
Bernie Devlin, a professor of psychiatry in the Department of Human Genetics at the University of Pittsburgh's Graduate School of Public Health, and Kathryn Roeder, a professor of statistics and computational biology at Carnegie Mellon University, worked on the study, which was conducted by researchers from Harvard and Yale and the University of Washington.
Researchers have believed that children inherit genes from their parents that cause autism. In these studies, scientists were able to focus on mutations that spontaneously occur in the womb.
The DeNovo sequence variants are risk factors for autism. DeNovo mutations are mutations that neither parent possesses but the child diagnosed with autism has.
"The rate of finding these variants in subjects with autism is slightly elevated over what we would expect from the population in general. Basically all of us carry DeNovo sequence events in our genomes. Some of them confer risks, some of them don't. It looks like in individuals with autism, there's a slight increase in that rate," said Devlin.
Local researchers worked on the project out of Yale and one that was sponsored by the National Institutes of Health and was scattered around the country.
They found that there are many genes that show these mutations, but in autistic children they cluster in three genes: KATNAL2, CHD8, and SCNAL2.
Its still too early to know how those genes might be connected to autism, but the researchers say these discoveries will play a key role in finding more autism genes.
"It's a breakthrough in the sense of a building block," said Roeder, "because now we have three." She added that there would be no new treatment based on these three.
"We've been slowly blinking away at different genes. We've been finding one at a time … now we expect to find another 30, 60, maybe 100 genes. We might find 20% of the genes within a year," said Devlin.
One of the studies also says the fetal mutations are more likely to come from the father's side, and moreso if the father is advanced in age.
"There's not as much of an increase in older fathers to explain the increase in numbers that's being seen in the CDC," said Devlin.
Another finding of the study is that there are 500-1,000 genes that affect risk for autism.
One of the studies looked at about 600 families where there was one child with autism, one child without, and two typical parents.
Autism is a brain disorder that affects social skills and communication skills, and can include repetitive and obsessive behavior. Those diagnosed can have mild or severe autism. In recent years, the numbers of those diagnosed has steadily increased. The most recent federal numbers estimate that 1 in 88 American children have an autism spectrum disorder. Males are more likely to be diagnosed than females.
"The nice thing about this study is that this is a tool by which we are now going to harvest many more autism genes," said Devlin.
There has also been an increasing amount of research into the environmental effects of autism. Devlin said that research is where genetics research was ten years ago.