Essential genes that are needed to survive and thrive in the womb play a critical role in the development of autism spectrum disorder, a new study has found.
An analysis of genetic samples of over 1,700 families from a repository showed that elevated levels of mutations in the "essential genes" was significantly associated with an increased risk for autism spectrum disorder (ASD) and decreased social skills.
Since brain function may be particularly sensitive to mutation accumulation, identifying specific sets of genes in which mutations have a behavioural effect may help understand they can result in diseases such as ASD, said researchers from the University of Pennsylvania in the US.
The new study shows that mice with ASD had much higher levels of damaging mutations in essential genes compared to their non-affected siblings.
Essential genes also constituted a significant fraction of known ASD risk genes.
"This makes our jobs harder, with respect to treatment, but these findings are absolutely critical for our understanding of the disease," said Maja Bucan, professor at the University of Pennsylvania.
"We know it is not one gene that is causing autism spectrum disorders - it is a background of mutations, which we know is important. Here, we show what this background is," said Bucan.
The findings suggest that ASD stems from an aggregate effect of many damaged essential genes that "work" together during the early stages of development in the womb, as soon as eight weeks after conception.
ASD is known as a polygenic disease, where many small gene effects contribute to a disorder, researchers said.
Hundreds of mutated genes have been previously implicated as the cause of this highly heritable, complex disease, but their importance, relationship with each other and function have not been entirely clear.
Researchers analysed almost 4,000 essential genes and 5,000 non-essential genes in 2,013 males with ASD and 317 females with ASD, as well as their siblings who did not have ASD, for known exonic de novo (began in the child) and inherited mutations.
They found that those with ASD had statistically significant elevated levels of mutatiions in essential genes compared to their siblings.
The essential gene mutations were associated with a higher risk of ASD and disruption in normal social behaviour, the researchers said.
On average, those with ASD had 44 per cent more early-in-childhood mutations and 1.3 per cent more inherited mutations in essential genes than their non-affected siblings.
The study was published in the journal PNAS.