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Reducing a protein in young mice with a condition resembling Down syndrome improves their ability to learn, researchers at UT Southwestern Medical Center have found [PLoS One, 5 (6): e10943]. The preliminary study raises "the intriguing possibility" that drugs lowering levels of the protein might offer some benefit to children with Down syndrome, said co-lead author Craig Powell, MD, PhD.
Down syndrome is caused by an extra copy of chromosome 21, which includes the genes for proteins that produce beta-amyloid. This protein accumulates in the brain of a person with Alzheimer's disease and is believed to contribute to cognitive decline.
Children with Down syndrome have increased levels of beta-amyloid in their brain, but it is unknown whether the increase affects intellectual abilities. Nearly all adults with Down syndrome develop signs of Alzheimer's by age 40, with dementia developing in their 50s and 60s.
Researchers used mice with a genetic anomaly that closely mimics human Down syndrome. This type of mice has three copies of a stretch of genes, including those related to beta-amyloid production, and display learning disabilities, including difficulties learning a standard water maze.
The scientists treated 4-month-old mice with DAPT, an experimental drug that blocks the enzyme essential for beta-amyloid production. Four days of treatment lowered beta-amyloid levels by 40 percent and significantly improved the rodents' performance to the point that they learned the maze as quickly as normal mice.
Dr. Powell cautioned that the blocked enzyme is involved in many brain functions besides creating beta-amyloid. "Inhibitors may have untoward side effects," he said. "The goal now is to identify drugs that block the ability of the enzyme to create amyloid without blocking its ability to perform other tasks."
The study was funded in part by the National Institutes of Health.
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