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Autism Cause: Brain Development Genes?

Genes Missing in Autism Needed for Learning-Triggered Brain Growth

Medically Reviewed by Brunilda Nazario, MD on July 10, 2008
From the WebMD Archives

July 10, 2008 -- Surprising findings from a gene study have set the world of autism research spinning on a new axis.

The new study shows that many of the different genes linked to autism -- and many of the new autism genes discovered in the course of the study -- are part of a network that allows a child's brain to build new connections in response to experience.

The good news is that a surprisingly large number of these mutant genes affect the on/off switches that control experience-triggered brain development. That's much better than missing the genes themselves, says study leader Christopher A. Walsh, MD, PhD, chief of genetics at Children's Hospital Boston and an investigator at the Howard Hughes Medical Institute.

"We are encouraged that some of these mutations do not seem to completely remove the gene altogether, but instead disrupt its on/off switches," Walsh tells WebMD. "That does offer hope we may be able to figure out other ways of activating the gene."

It's a big deal, says Thomas Insel, MD, director of the National Institute of Mental Health.

"We can begin to think of autism as a disease of synapses, of the way connections are developing in the brain," Insel tells WebMD. "This is really quite intriguing. It adds another region for science to go after to look for new targets for either autism treatment or prevention. It is a very important step."

Autism is a spectrum of different disorders ranging in severity and in symptoms. But all autism disorders have certain things in common: impaired social interactions, impaired communication, and stereotyped interests and behaviors.

The new findings offer a unifying theory, suggesting that many forms of autism result from specific defects that affect a child's ability to learn and remember.

Genetics plays a major role in autism. The mutations that cause fragile X syndrome and Rhett's syndrome result in autism. But unlike diseases such as cystic fibrosis, the vast majority of autism cases can't be traced to a single mutation. Instead, a growing number of different genes have been linked to a growing percentage of autism cases.

"We still don't understand the underlying genetics for more than half the kids with autism, so we have a long way to go to understand that, and to understand what non-genetic factors might also contribute," Walsh says. "We know genetics is very, very important in autism, but we don't know whether it is the whole answer or not."

The Walsh team's findings are "really exciting," says Margaret A. Pericak-Vance, PhD, director of the Miami Institute for Human Genomics at the University of Miami School of Medicine. But she, too, notes that it's far from the end of the search for the causes of autism.

"Autism, even though it has a heritable component, is a complex disease that will take a lot of different approaches to decipher," Pericak-Vance tells WebMD. "It will not be one-stop shopping. We know there is no single major cause and no simple answer."

Pericak-Vance predicts that researchers scanning the entire human genome for autism clues will soon be announcing more "exciting" results.

Crucial to the Walsh team's findings was the collaboration of scientists in Jordan, Kuwait, Oman, Pakistan, Qatar, Saudi Arabia, Turkey, and the United Arab Emirates. These researchers enrolled 104 families in the study, including 88 families with marriages among cousins. That was an important factor, as rare or recessive genes occur twice as often in such families.

But also crucial was a chance meeting between Walsh, a geneticist, and fellow Children's Hospital Boston/Harvard researcher Michael E. Greenberg, PhD, a neuroscientist studying how the brain changes as it learns.

"When we talked to each other, we realized, gee, a lot of our genes that are involved in autism are also their genes that are involved in learning in the brain," Walsh says. "There is nothing more powerful in science than these kinds of serendipitous collisions between people working in related but somewhat distinct fields."

Walsh and colleagues report their findings in the July 11 issue of the journal Science.

(Just found out your child has autism? Come meet other parents who understand at WebMD's Autism Support Group.)

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Sources

SOURCES:

Morrow, E.M. Science, July 11, 2008; vol 321: pp. 218-223.

Sutcliffe, J.S. Science, July 11, 2008; vol 321: pp. 208-209.

News release, Howard Hughes Medical Institute.

News release, Children's Hospital, Boston.

News release, National Institute of Mental Health.

Christopher Walsh, MD, PhD, chief of genetics, Children's Hospital Boston; investigator, Howard Hughes Medical Institute, Beth Israel Deaconess Hospital; and professor of neurology, Harvard Medical School, Boston.

Margaret A. Pericak-Vance, PhD, director, Miami Institute for Human Genetics, University of Miami School of Medicine.

Thomas Insel, MD, director, National Institute of Mental Health, Bethesda, Md.

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