Researchers find new information on causes of autism

The number of children diagnoses with autism is increasing rapidly, according to the latest statistics.

According to the latest figures from the Centers for Disease Control and Prevention, in the United States one child in 88 has autism. The incidence has been rising steadily and rapidly, up 80 percent in a decade. It’s not believed that there’s actually an increase in the number of children with autism, just that the number of diagnoises is increasing.

Researchers have long believed genetics play an important role in autism. But they lacked hard evidence, until now. New research, though, has linked genetics with autism, through studies that were not even possible just a couple of years ago.

Three independent studies published in the latest edition of Nature reveal a link between genetics and autism. Researchers sequenced the genomes of children with autism and their parents to discover mutations in their genes.

Professor Mark Daly, analytic and translational genetics chief at Massachusetts General Hospital, is lead author of one of the studies.

“We were targeting a very specific type of mutation — that is, those that arise spontaneously, and we were able to detect in each of those kids with autism whether or not they had specific mutations,” Daly explained.

They found children with autism had nearly twice as many severe mutations in their genetic code. If these mutations occur in an important protein-causing gene, they could disable that copy of the gene.

Daly said the majority of individuals and children with autism actually do not have the specific mutations found in the study, but, “the fact that there were more of them in the kids with autism allowed us to pinpoint very confidently a small number of genes as genuine risk factors for autism.”

Researchers estimate that the mutated genes found in the study were responsible for only 1 percent of autism. Researchers found three or four genes that are very likely to contribute to autism in about 1 percent of children.

“That leads us to extrapolate in a way that’s consistent with previous studies — that there are actually hundreds of genes that contribute to autism risk,” Daly said.

Though no clinical test for this genetic mutation has been developed, Daly said it’s possible for one to evolve from further studies. Further studies may also identify a link between autism and the environment.

“I think it’s clear that genes by itself do not cause autism in the way that a single gene causes Huntington’s disease or cystic fibrosis. Now it’s hard at this point of our evolution of genetics, since we’ve only discovered a small fraction of the responsible genes, but that doesn’t preclude the potential for very, very important environmental factors from also contributing to a large majority of cases,” Daly said.

Dr. Irva Hertz-Picciotto thinks research along both fronts — genetic and environmental — will be important.

Hertz-Picciotto is investigating possible environmental causes as the principal investigator at the UC Davis Center for Childhood Autism Risks from Genetics and the Environment.

She said research into autism and the environment needs more attention.

“I think that most cases of autism have some genetic susceptibility factors, but that those susceptibility factors are not enough to cause outright autism by themselves. That only in combination with environmental factors do you actually get autism,” she said.

According to Hertz-Picciotto, one study found that women who reported they took their prenatal vitamin supplements before they conceived appeared to be at an almost 40 percent reduced risk of having a child who later developed autism. She believes it may have been the folic acid in the prenatal vitamins that helped deter autism.

“What we also saw in that study was that the risk was modified by either the mother’s or the child’s genes that pertains to the metabolism of folic acid. So if they had a high risk, or inefficient metabolism of the folic acid, then they were at substantially higher risk,” Hertz-Picciotto said.

Another study looked at the effect of exposure to air pollution during pregnancy.

“We looked at where the homes were — where the mom resided at the time that she was pregnant — and we linked that to the roadway system in California. Then we said where’s the closest freeway to that woman’s house, and if she lived close to a freeway, within three quarters of a mile, there was a higher risk that her child would develop autism,” Hertz-Picciotto said.

Researchers also found that exposure to solvents and chemicals may be associated with a higher risk for autism. Finding the absolute cause or causes of autism, though, is extremely difficult, partly because diagnosing autism in and of itself is an extremely complex process.

Harvard researcher Dennis P. Wall believes he has found a way to diagnose autism within minutes rather than the hours it typically takes to get a diagnosis. According to a Time magazine report, Wall, director of the computational biology initiative at Harvard Medical School, may have found a method to replace the evaluations currently used.It combines computer algorithms along with a seven-point parent questionnaire and a home video clip to make a speedy online assessment of whether a child has autism.

Though Wall’s discovery may help provide the push researchers need to better understand autism, Hertz-Picciotto said there is still more work to be done.

“There is no systematic testing starting in the prenatal gestational period to look at neuro-development. And that’s the question — we don’t have a specific system to study those chemicals that get introduced,” Hertz-Picciotto said.