CHICAGO (Reuters) – A study on hundreds of families with autism revealed that spontaneous mutations can occur in the sperm or the egg of the parents that increase the risk of a child developing the disorder.
Parents are four times more likely than mothers to move these mutations to their children, reported scientists.
The results of three new studies published in the journal Nature, suggest that mutations in the part of the gene that encodes proteins – called the exoma – play an important role in autism.
And while these genetic errors can occur in the genetic code, and many would be harmless, can cause major problems when they occur in parts of the genome necessary for the development of the brain.
One of the three teams found that these errors would lead to between five and 20 times higher risk of developing autism.
“These results confirm that it is not the size of the genetic anomaly that bestows the risk, but its location,” said Dr. Thomas Insel, director of the National Institute of Mental health, part of the national institutes of Health’s United States, it funded a research.
Among other findings, the team – led by Mark Daly of the Massachusetts Institute of technology, Dr. Matthew State of Yale University and Evan Eichler of the University of Washington in Seattle – identified several hundred new suspicious gene that could lead to new targets for the treatment of autism.
Many of the researchers were part of the so-called collaboration for the sequencing of autism, the greatest effort in its kind for using advanced genetic sequencing technology to identify the underlying genetic issues in autism.
Autism encompasses a broad spectrum of disorders ranging from the serious to communicate disability and mental retardation to relatively mild symptoms, such as Asperger’s syndrome.
In United States, about one of every 88 children suffering from autism, according to the latest statistics from the Centers for Disease Control and the prevention of (CDC for its acronym in English).
While scientists believe that genetics represents between 80 and 90 percent of the risk of developing it, the majority of cases of autism can not be traced to a common hereditary cause.
Experts previously found dozens of genes that raise the risk of autism. But the genetic causes explain only about 10 percent of cases, and recent studies detected environmental factors, possibly from conception, as possible triggers of the disorder.
Sequencing
For this study, the researchers sequenced data of 549 families involving both parents and a son with autism.
Joseph Buxbaum, director of the Center for autism in the school of Medicine of Mount Sinai in New York and co-author of one of the works, said that the combined results of the three studies suggest that about 360 to 1,200 genes contribute to the risk of developing autism.
How difficult is identifying the specific networks of the brain in which these genes interact so researchers can begin to develop new therapies.
“Now have a finished idea that the large number of genes involved in Autism”, said Buxbaum.
Was suggested by one of the studies, Dr. Evan Eichler and colleagues from the University of Washington in Seattle, how environmental factors would influence genetics.
Researchers looked specifically to see whence came these genetic errors that occurred spontaneously: sperm from the father or the mother’s ovum.
The team found that generated new mutations with four times more often in that sperm on the eggs, and that bigger was the father, was more prone to have sperm with these spontaneous variations.
A possible explanation for this, said Buxbaum, is that men produce sperm every day, and this high renewal rate increases the chances of occurring errors in the genetic code that could be moved to children.
“This tells us that the sperm production is an imperfect process”, said Buxbaum in a phone interview.
“Is fundamentally directed by paternal age.” That makes sense. “As one ages, are increasingly more likely problems”, he added.
Buxbaum pointed out that these results support those of other studies have shown that older parents have more risk of having a child with an autism spectrum disorder.
The expert emphasized that everyone has these small errors in the genetic code, but when they occur in key areas of brain development, they can cause different types of autism.
(Published in Spanish by Ana Laura Mitidieri)
