Brain Defect Helps Drive Fragile ...( The condition is leading cause of inh...),Health

The condition is leading cause of inherited mental retardation

THURSDAY, Sept. 20 (HealthDay News) -- A newly discovered brain defect might be a target for the treatment of the inherited mental disorder known as fragile X syndrome, researchers report.

The discovery in rats provides an understanding of how the gene mutation responsible for the condition changes the way brain cells communicate, according to the report in this week's issue of the Proceedings of the National Academy of Sciences.

"Fragile X syndrome is the most common form of inherited mental retardation," explained co-author Gary J. Bassell, a professor of cell biology at Emory University in Atlanta. "It has strong links to autism and epilepsy."

Fragile X syndrome occurs in approximately one in 4,000 males and one in 8,000 females, Bassell noted.

Working with rat brain cells, the team found that synapses between brain cells in the part of the brain called the hippocampus are defective in animals with fragile X, Bassell said.

"We discovered what the specific underlying defect is," he said. "It is actually a defect in the mGluR5 receptor, which is on the surface of neurons. The defect is that there is excessive signaling."

Children with fragile X have difficulty in processing information, because these receptors allow too much signaling and change the function of other receptors, Bassell theorized.

When his team treated the receptor with an mGluR5 antagonist called MPEP, they were able to reverse the effects of the mutation. "When you quiet down this receptor, it corrects the defects that occur in other receptors as well," he noted.

Bassell stressed that MPEP is not a suitable drug for humans. However, the discovery should help researchers find other drugs that do the same thing safely.

Any drug that targets the receptor will not be a cure for fragile X, Bassell cautioned. "These childr
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