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    Gene Interaction Linked to Autism Risk

    Researchers 'on the Right Path,' Expert Says
    WebMD Health News

    Aug. 3, 2005 -- It has long been believed that complex genetic interactions are at play in autism, and new research offers some of the first concrete evidence that this is the case.

    For the first time, researchers have identified an interaction between two specific genes that increases the risk that a child will develop autism. Both of the genes are associated with a chemical in the brain that has been a target of autism research for the past decade.

    "This is exciting because it tells us that researchers seem to be on the right path and that we may be starting to understand the brain pathology (of autism)," says Andy Shih, PhD, who is chief science officer for the National Alliance for Autism Research, which helped fund the new study.

    Autism is characterized by communication problems, social impairment, and unusual or repetitive behaviors.

    Genes and Environment

    It is widely thought that autism risk is determined by a combination of unidentified genetic and environmental factors. Children born into families with one autistic child are known to be at greater risk of developing autism, but the extent of that risk is not well understood.

    Autism researcher Margaret Pericak-Vance, PhD and colleagues with Duke's Center for Human Genetics have long studied a brain chemical associated with slowing or stopping nerve activity, known as GABA. The GABA system acts as something of an information filter to prevent the nerves from becoming overstimulated.

    It has long been suspected that this filtering process is compromised in many autistic children. Impairment of the GABA system could overwhelm the brain with sensory information, leading to many of the behavior traits associated with autism.

    GABA is believed to play a key role in the early development of the brain, and the Duke researchers and others have previously shown a connection between GABA and autism.

    In their latest study, Pericak-Vance and colleagues examined 14 genes that help make parts of the GABA receptor. The receptors allow the chemical to affect nerve function.

    The participants in the study were 470 Caucasian families with at least one autistic member; 266 families had more than one member with autism.

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