http://news.yahoo.com/s/hsn/20061016/hl_hsn/genemutationlinkedtoriskof
autism

by Ed Edelson
HealthDay Reporter
Mon Oct 16, 7:03 PM ET



MONDAY, Oct. 16 (HealthDay News) -- For the first time, researchers
have identified a specific gene mutation that increases the risk of
autism.

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And while scientists are hailing the discovery as significant, they
add that it will be many years before the research has medical
applications.


The study of more than 700 families with autistic children found that
a mutation that decreases the production of a protein designated MET
more than doubles the risk of the disorder.


The report, led by researchers at Vanderbilt University in Nashville,
Tenn., was published in this week's issue of the Proceedings of
the National Academy of Sciences.


"Rare changes in genes have been identified before this as
contributing to the risk of autism," said Dr. Matthew W. State,
director of the Yale University School of Medicine's program on
neurogenetics, who wrote an accompanying commentary in the
journal. "Conversely, there have been a number of instances where a
gene has been implicated, but where the functional change that led to
the finding was not found."


"This time, they have gone all the way, identifying the gene and the
mechanism. It is tremendously important because it tells you what the
biological processes might be," State added.


Autism is a disorder that causes social deficits, language impairment
and repetitive behavior. Its reported incidence has increased sharply
in recent years, perhaps because of more awareness of the condition.
The incidence of autism itself is estimated at one in every 500
American children, and the rate of autism-related conditions is as
high as one in 166.


The MET protein studied by the researchers has many roles in the
body. It is best known for promoting metastasis, the spread of a
variety of cancers. But it also has been found to contribute to
immune function and gastrointestinal repair. Recent studies, by the
Vanderbilt group and others, have shown that the protein contributes
to development of the cerebral cortex and cerebellum, parts of the
brain that can be abnormal in people with autism.


This study found that a mutation of the portion of the MET gene that
governs the production of its protein was associated with the risk of
autism. The strongest association of the mutation to autism was found
in families with more than one affected child. Overall, the presence
of the mutation raised the risk of autism by 2.27 times.


An essential step now is to verify the finding, said Andy Shih,
director of research at the National Alliance for Autism Research.


"Maybe 100 candidate genes have been identified before this, and most
of them have not been replicated," Shih said. "But what distinguishes
this particular paper is that it involves the biology associated with
this condition."


Now that a mutation has been identified, Shih said, "we must try to
understand how this functional variant is related to behavioral
manifestations."


State said: "The first thing always is that this absolutely must be
replicated in other laboratories. Second, in terms of understanding
the biology better, we have to take a look at what happens in vivo,"
meaning in physical function.


One possible method of verifying the finding would be to bioengineer
animals such as mice so their production of MET protein is reduced,
to see how that affects their behavior, State said.


But, Shih added, any medical application of the finding is many years
away.


More information


To learn more about autism and related disorders, visit the U.S.
National Institute of Mental Health.