Autism Risk Higher In People With Gene Variant

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http://www.nih.gov/news/health/jan2008/nimh-10.htm

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Thursday, January 10, 2008

Autism Risk Higher in People with Gene Variant

Difference in Gene Appears to Pose More Risk When Inherited from

Mothers

Scientists have found a variation in a gene that may raise the risk

of developing autism, especially when the variant is inherited from

mothers rather than fathers. The research was funded by the National

Institute of Mental Health (NIMH), part of the National Institutes of

Health.

Inheriting the gene variant does not mean that a child will

inevitably develop autism. It means that a child may be more

vulnerable to developing the disease than are children without the

variation.

The gene, CNTNAP2, makes a protein that enables brain cells to

communicate with each other through chemical signals and appears to

play a role in brain cell development. Previous studies have

implicated the gene in autism, and in this study researchers were

able to link a specific variation in its structure to the disease.

Results of the study were reported online January 10 in the American

Journal of Human Genetics, by Aravinda Chakravarti, Ph.D., Dan E.

Arking, Ph.D., and colleagues from the s Hopkins University

School of Medicine, with Edwin Cook, M.D., and colleagues from the

University of Illinois at Chicago.

" Autism is highly heritable. Identifying the genes involved is

crucial to our ability to map out the pathology of this isolating and

sometimes terribly disabling disease, which currently has no cure, "

said NIMH Director R. Insel, M.D.

Autism is a developmental brain disorder that impairs basic behaviors

needed for social interactions, such as eye contact and speech, and

includes other symptoms, such as repetitive, obsessive behaviors. The

symptoms sometimes cause profound disability, and they persist

throughout life. Treatments may relieve some symptoms, but no

treatment is fully effective in treating the core social deficits.

Although the cause of autism is not yet clear, studies of twins have

shown that genes play a major role. It is likely that variations in

many genes, influenced by environmental factors, interact during

brain development to cause vulnerability to the disease. These genes

have yet to be identified. Several candidates, including CNTNAP2,

have been suggested.

The assertion that the CNTNAP2 gene appears to be involved is

strengthened by the fact that each of the different analytical

approaches the researchers used in this study led to the same

conclusion. Results were replicated in a second, larger group of

participants, further implicating the gene. Together, the two groups

of participants comprised one of the largest autism studies reported

to date.

The first part of the study included 145 children with autism and

their parents, families that had two or more children with autism.

Using a technique called genome-wide linkage analysis, the

researchers found that a chromosome, 7q35, appeared to be linked to

the disease.

Looking deeper into that chromosome, they identified a gene —

CNTNAP2 — that contained a variant relevant to autism. Where a single

segment of the genetic code could contain either the chemical base

adenine or thymine, children with autism tended to have inherited the

thymine variant.

To validate these findings, the researchers studied a separate group

of participants; 1,295 children with autism and their healthy

parents. The scientists again found that children with autism had

higher rates of the thymine variant in the CNTNAP2 gene than would be

expected to occur by chance.

When the researchers combined the data from the studies, they found

that children with autism were about 20percent more likely to have

inherited the thymine variant from their mothers than from their

fathers.

" This is a common variant. People inherit it all the time. Our

finding that it's associated with autism more often when it's

inherited from mothers is intriguing, but needs to replicated, "

Chakravarti said.

The role of CNTNAP2 in brain-cell development suggested by earlier

studies has to do with differentiation, the process by which

precursor cells develop into the different kinds of cells of the

body. CNTNAP2 carries the genetic code for a protein, part of a

family called neurexins, that appears to enable the precursor cells

to develop myelinated axons. These are projections through which

brain cells send each other electrical impulses essential for normal

brain function at especially high speeds.

" CNTNAP2 is an excellent candidate gene for autism, " Chakravarti

said. " It encodes a protein that's known to mediate interactions

between brain cells and that appears to enable a crucial aspect of

brain-cell development. A gene variant that altered either of these

activities could have significant impact. "

For more information about autism, visit the NIMH website at

http://www.nimh.nih.gov/health/topics/autism-spectrum-disorders-

pervasive-developmental-disorders/index.shtml.

More information about autism also is available from the Department

of Health and Human Services (DHHS) website at

http://www.hhs.gov/autism/.

The National Institute of Mental Health (NIMH) mission is to reduce

the burden of mental and behavioral disorders through research on

mind, brain, and behavior. More information is available at the NIMH

website: http://www.nimh.nih.gov/.

The National Institutes of Health (NIH) — The Nation's Medical

Research Agency — includes 27 Institutes and Centers and is a

component of the U.S. Department of Health and Human Services. It is

the primary federal agency for conducting and supporting basic,

clinical and translational medical research, and it investigates the

causes, treatments, and cures for both common and rare diseases. For

more information about NIH and its programs, visit www.nih.gov.

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Reference:

Arking DE, Cutler DJ, Brune CW, Teslovich TM, West K, Ikeda M, Rea A,

Guy M, Lin S, Cook Jr. EH, Chakravarti A. A common Genetic Variant in

the Neurexin-Superfamily Member CNTNAP2 Increases Familial Risk of

Autism. American Journal of Human Genetics, online ahead of print,

January 10, 2008.

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>

[Guest guest]

Hmmmm.. this could explain for dh’s side of the family, it came from his

mom, passed his sister over but they have a son with asperger’s.

I have no hx of autism on my side though…so david and had to have

gotten it passed down from Papa.

Nita, Mom to: 14, Jon 13, 10, 8, 6, Christian

(7/16/03 to 8/22/04), 2 and Isaac due Feb. 08

Learn from the mistakes of others. Trust me... you can't live long

enough to make them all yourself.

.._,___

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