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Genetics researchers are reporting some exciting progress in the search for a cure for genetic brain-wasting diseases like Huntington's disease. These painful, fatal diseases often don't cause symptoms until after their victim has passed it on to their children. This ScienCentral News video has more.
Potential Hope
Huntington's Disease is a devastating inherited disorder in which brain cells are genetically programmed to degenerate. The disease, which can cause dementia, memory loss, loss of movement control, and ultimately death, can strike people as young as 30; there is currently no cure. But now, genetics researchers at the University of Iowa have shown they can rescue mice from a disease similar to Huntington's using gene therapy.
Humans have two copies of most genes. Huntington's disease is one of several neurodegenerative diseases in which an error in the DNA code of just one copy of a gene causes the disease. While the normal gene tells brain cells how to build a needed protein, and the bad copy results in a toxic protein that kills brain cells.
Beverly Davidson, professor of internal medicine, physiology and biophysics, and neurology at the University of Iowa, and her group treated young mice with another dominant genetic neurodegenerative disease called spinocerebellar ataxia type 1 (SCA1). They reported in the journal Nature Medicine that they treated the mice with a technique called RNA interference, or RNAi, which uses small sequences of the genetic material RNA designed to block the cell's machinery from making a protein encoded by a specific gene—in this case, halting the production of the toxic protein. The researchers used a harmless virus to carry the RNA into brain cells.
Rotating rods are used to test balance.
"This is the first time that RNA interference has been accomplished in living tissues within animals that have a degenerative brain disease," says Davidson. And the results were promising—the mice with the SCA1 gene that received the gene therapy had normal coordination and movement. "The mice are much better," she says. "The mice appear almost as if they've had no disease. We've been able to essentially halt the disease from progressing from the initiation of the therapy." In contrast, in the mice with the SCA1 gene that were not treated, the disease progressed, causing lost brain cells and movement problems.
"The first reaction I had when I saw that we could improve the behavior in these mice was, 'Wow!'" says Davidson. "It was almost unbelievable—how could the simple methods that we were using lead to such a profound impact on the disease in these mice?"
Davidson also found that the RNA interference itself doesn't seem to be toxic to normal brain cells. She is optimistic about RNAi's potential to treat neurological diseases like SCA1 and Huntington's in humans. According to the researchers, the same technique could also apply to other neurodegenerative disorders that could be halted by inhibiting production of a mutated (or "toxic") protein, such as Alzheimer's Disease.
"A year ago the challenge was how do we move from accomplishing this in cells in a dish to accomplishing this in cells in the brain, and it's delightful that we're there, we've done it," says Davidson. "The question now is how do we move it from a little bitty brain the size of the mouse brain, into human therapies. And that's the next challenge."
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