Scientists at Tufts University have identified a molecular mechanism that could reverse the genetic defect responsible for Friedreich's ataxia, a neurodegenerative disease that leaves its victims with difficulty walking, a loss of sensation in the arms and legs and impaired speech caused by degeneration of nerve tissue in the spinal cord.
The researchers report today in the Proceedings of the National Academy of Sciences that the genetic anomaly that causes the disease -- the multiple repetition of a three letter DNA sequence -- could potentially be reversed by enhancing a natural process that contracts the repetitive sequences in living tissue.
Friedreich's ataxia is a genetic disease caused by the presence of an expanded repetition of a three letter genetic sequence, GAA in the FXN gene, which encodes for frataxin, a protein required for proper function of the mitochondria -- the cell's "batteries" that generate the fuel to keep all other cell functions running.
Healthy people usually have 8 to 34 GAA repeats, carriers have 35 to 70 repeats, and individuals that exhibit disease symptoms have more than 70 -- and commonly have hundreds of repeats.
With more DNA repeats, it becomes increasingly difficult for the cells to "read" the FXN gene and produce the protein required by the mitochondria, which in turn cease to function properly. One in 40,000 individuals has this condition.
The DNA repeats literally gum up the works. They can also cause other mutations in the surrounding DNA, or make chromosomes extremely fragile, breaking into pieces, or rearranging themselves. If we can shrink the DNA repetition in tissues to levels found in healthy people, we might be able to stabilize the DNA and reduce the effects of disease." Sergei Mirkin, professor and chair, Department of Biology, School of Arts & Sciences, Tufts University
It is known that in patients' tissues, the GAA repeats are unstable and continuously expand and contract. Understanding the mechanism of GAA repeat expansion and contraction -- especially contraction -- is important to developing this strategy for battling the currently incurable disease. Related Stories
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