Gene duplications responsible for autism could have developed in humans relatively recently.
New research suggest the region of the genome responsible for autism evolved over only the past 250,000 years, after humans diverged from ancient hominids, the American Society of Human Genetics reported.
To make their findings the researchers looked at the genomes of "2,551 humans, 86 apes, one Neanderthal, and one Denisovan." They examined a region of the human chromosome called 16p11.2, which has been linked to autism. The team observed that certain DNA in this region is repeated in some people, which also could have implications for the disease. To trace these variations the researchers sequenced the same region of apes' genomes.
"When we compared the genomes of apes and humans, we found that the humans had evolved complex structural changes at 16p11.2 associated with deletions and duplications that often result in autism. The findings suggest that these changes emerged relatively recently and are unique to humans," said study author Xander Nuttle, a graduate student in the Department of Genome Sciences at the University of Washington School of Medicine.
The team believes these genetic variations have left humans more susceptible to certain diseases, and could have led to the formation of genes such as BOLA2. This novel gene is believed to be responsible for cell reproduction; modern humans possess between three and 14 of these genes while apes have only two.
"Another question we are exploring is why people with the same duplications and deletions at 16p11.2 vary in disease severity," Nuttle said. "Some people are healthy or have mild illness, while others are severely affected and have multiple clinical diagnoses."
The researchers suggest factors, such as where in the genome the deletions and duplications take place, has an effect on the variability of genes such as BOLA2.The team is now working on a study of 125 individuals with deletions or duplications at 16p11.2.
"We believe this work will lead to new insights about the genetic underpinnings of autism and other conditions associated with 16p11.2 deletions and duplications, potentially paving the way for more specific diagnostics and treatments for patients in the future," Nuttle said.
The findings were presented at the American Society of Human Genetics (ASHG) 2014 Annual Meeting in San Diego.
