Scientists Take a Closer Look at Autism Genes
Using advanced computer technology, California researchers discover mutation hotspots in the human genome that are linked to autism.
--by Suzanne Boothby
Genes linked to the development of autism are more prone to frequent mutation than average genes, according to new research published in the journal Cell.
The new research suggests that higher mutation rates in certain parts of the genome contribute to disease risk.
"Some disease-related genes are gluttons for punishment," said senior study author Jonathan Sebat of the University of California, San Diego. "Despite the fact that these genes are important for normal human development, they appear to be getting hammered with mutations."
He explained that every child born has a certain number of genetic mutations that are essentially random. Neurodevelopmental disorders, such as autism, are associated with deletions and duplications of DNA in specific regions of the genome that tend to mutate at a high rate, but this new discovery illuminates the frequency of mutations in these "hotspot" areas.
“These hotspots are influencing disease risk, and their prevalence is probably being influenced by these hotspots,” Sebat said. “If you have a gene that when mutated can cause autism and the [mutation] rate is 10 times higher than average, that gene is going to have a bigger influence.”
The Expert Take
“We were able to hone in on certain genes and, most importantly, spontaneous mutation,” Sebat said. “These genes are not inherited, but are actually new mutations, and with autism, it’s a glitch that arises spontaneously.”
This first attempt to understand mutation hotspots was made possible through better access to technology that can model the entire human genome.
"This is truly the first chance anyone has had to explore the landscape of mutability in humans because an unbiased look at patterns of mutation in the genome was impossible before the development of high-throughput sequencing technologies," Sebat said.
Source and Method
The research team performed whole-genome sequencing on identical twins with an autism spectrum disorder and on their parents.
They found mutation clusters in certain parts of the genome using advanced computing techniques modeling how mutations occur. Mutation rates varied by as much as 100-fold across the genome, and this variation could be explained by intrinsic properties of genetic material, such as characteristics of the DNA sequences and how DNA is packed.
Sebat said that the next step is to find more families to test in order to continue to study these genetic hotspots.
“We see a lot of potential benefit in focusing on these hotspots in larger numbers of families,” he said. “Some major genes exist inside of these hotspots, and by mapping out mutations we can try to identify new genetic causes of disease.”
A 2007 study conducted by Sebat and colleagues also found that spontaneous mutations can boost autism risk and motivated the research team to continue examining the genome.
“Our results show conclusively that these tiny glitches are frequent in autism, occurring in at least ten percent of cases, and primarily in the sporadic form of the disease, which accounts for 90 percent of affected individuals,” Sebat said in 2007 statement.