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    USF team finds gene link to Alzheimer's


    © St. Petersburg Times, published September 26, 2000

    TAMPA -- They don't know how or why, but a common variation of a gene may nearly double your chances of getting Alzheimer's disease after age 80, researchers at the University of South Florida have discovered.

    Their findings are published in today's issue of the journal Neurology, the standard-bearer for news and research about neurological science. The discovery adds one more piece to the puzzle of how Alzheimer's strikes.

    The correlation between the gene, cystatin C, and Alzheimer's eventually may prove helpful in diagnosing and treating the degenerative brain disorder, which afflicts about 4-million Americans.

    "It tells us that this cystatin C protein plays some role in the disease process," said Dr. Fiona Crawford, the associate director of USF's Roskamp Institute for Alzheimer's Research and the lead author and investigator of the study.

    "Because we're looking at late-onset disease, we're looking for things that have a subtle effect ... a gradual, slow effect. This suggests that some function of the cystatin C protein is significant in moving the disease forward."

    Everyone carries the cystatin C gene, and everyone has one of three variations of it: labeled AA, GG or AG.

    Researchers at USF, the University of Miami and several independent sites studied 309 people with Alzheimer's and 134 people without it. All were the between the ages of 60 and 90.

    Among Alzheimer's patients between 80 and 90, 52 had the GG variation and 27 did not, the study said. Among those without Alzheimer's, less than half had the GG variation.

    Only one gene, known as APOE-4, definitively has been linked to Alzheimer's, but many other genes are being studied. This marks the first time that cystatin C has been linked to Alzheimer's, and further study is needed to determine how strong that link is or what role it plays.

    APOE-4 seems to increase the chances of developing Alzheimer's only in people who are between 60 and 80. After 80, APOE-4 doesn't seem to have any effect.

    Since cystatin C seems to affect people only after age 80, the USF study suggests different genes may influence Alzheimer's at different times of life, Crawford said.

    "We know there's got to be something going on in the over-80 set, and we know it's not all going to be environmental," she said. "We know there are going to be some genetic factors, and that's what we seem to have found here."

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