NEW YORK - Three teams of scientists working independently to understand the biology of autism have for the first time homed in on several gene mutations that they agree sharply increase the chances that a child will develop the disorder, and have found further evidence that the risk increases with the age of the parents, particularly the father.
The gene mutations are extremely rare and together account for a tiny fraction of autism cases, suggesting that the search for therapies will be a long one, and that what is loosely known as autism may represent a broad category of related but biologically distinct conditions. There are probably hundreds, perhaps thousands, of rare mutations that could disrupt brain development enough to result in social and developmental delays.
But specialists said that the overlapping results - reported in three papers posted online Wednesday in the journal Nature - give scientists working on the genetics of autism something they have not had: a clear strategy for building a real understanding of the disease’s biological basis. Researchers hope to find more similar, rare mutations in the next year or so that they estimate could account for 10 percent to 20 percent of all cases.
Biologists have been groping in vain for a reliable, verifiable foothold from which to investigate the underlying genetics of so-called autism spectrum disorders, including Asperger’s syndrome and related social difficulties that are being diagnosed at alarmingly high rates - on average, in one of 88 children, according to a government estimate released last week.
Previous studies have produced a scattering of gene findings but little consensus or confidence in how to proceed.
The new work provides a measure of both, and strong backing for earlier studies linking autism to the age of new fathers.
“These studies aren’t so much a breakthrough, because we knew this was coming,’’ said Jonathan Sebat, a geneticist at the University of California, San Diego, who was not a part of the research teams. “But I’d say it’s a turning point. We now have a reliable way forward.’’
Other researchers were more cautious, saying that the genetics of rare mutations were not yet well enough understood to make conclusive statements about their effect on the behavior of specific genes.
“This is a great beginning, and I’m impressed with the work, but we don’t know the cause of these rare mutations, or even their levels in the general population,’’ said Dr. Aravinda Chakravarti, of the Institute of Genetic Medicine at the Johns Hopkins University Medical School, who was not involved in the studies.
The three research teams analyzed genetic material taken from blood samples of families in which parents who have no signs of autism gave birth to a child who developed the disorder.
This approach gave scientists the opportunity to spot the initial mutations that accompany the condition.