TUESDAY, Aug. 8, 2006 (HealthDay News) -- While the origins of Parkinson's disease remain largely unknown, a new study confirms that a single gene is the likely culprit in about 3 percent of cases.
The alpha-synuclein (SNCA) gene might also be a key player in a wider range of Parkinson's cases, the researchers said.
"Common variants in the SNCA gene are associated with an increased risk for Parkinson's disease," said lead researcher Dr. Demetrius M. Maraganore, from the Mayo Clinic College of Medicine. His team reported the finding in the Aug. 9 Journal of the American Medical Association.
Parkinson's disease is a degenerative neurological condition associated with impaired motor skills and shortened life expectancy. Up to one million Americans suffer from the disease, for which there is currently no cure, according to the Parkinson's Disease Foundation.
"We know that Parkinson's disease is a complex disease," Maraganore said. "It isn't caused by any single factor. It's caused by multiple factors. Those factors may be genetic or environmental. But we know, with confidence, that alpha-synuclein gene variation is one of the puzzle pieces that belongs to the big picture of Parkinson's disease."
In their study, the researchers examined whether variability in the dinucleotide repeat sequence (REP1) of the SNCA gene was associated with the risk of Parkinson's.
To do so, they compared data on the gene variation in patients with Parkinson's disease and in people without the condition. In all, the researchers compared 2,692 Parkinson's patients to 2,652 people without the disease.
Maraganore believes the new finding has therapeutic implications.
"We know that everyone with Parkinson's disease has abnormal accumulations of alpha-synuclein protein -- the protein that is made by the alpha-synuclein gene," Maraganore said. In fact, he said, "The hallmark of Parkinson's disease in the brain is abnormal clumps of alpha-synuclein."
In studies of families where more than one family member had Parkinson's disease, an over production of alpha-synuclein seems to be enough to trigger the disease, Maraganore pointed out. So, "What we can say from this study is that this is a common cause of Parkinson's disease," he said. "This really justifies efforts to develop treatment to reduce the production of alpha-synuclein."
Reducing the amount of alpha-synuclein produced by this gene may reduce a person's likelihood of developing Parkinson's disease, Maraganore said. "What we don't know is whether, in a person with Parkinson's disease, reducing alpha-synuclein would modify disease-related outcomes," he said.
However, Maraganore believes that reducing alpha-synuclein in people with Parkinson's disease might help slow or halt its progression.
One expert agreed that the gene and its protein could be a target for treatment.
"This is not the first paper to suggest that changes in SNCA may contribute to Parkinson's disease," said Dr. Robert Edwards, an associate professor of neurology and physiology at the University of California, San Francisco.
What this paper shows is that if you make more of the protein made by this gene, you are at greater risk for Parkinson's, and if you make less of it, you are at less risk, Edwards explained.
"This protein probably does have a role in all Parkinson's, as well as these rare [cases of] familial Parkinson's," Edwards said. However, the risk is very small, he noted. "It cannot account for that much of why someone gets Parkinson's and others do not," he added.
Edwards believes drugs could be developed that could reduce the levels of alpha-synuclein to help prevent Parkinson's and also treat those living with the disease.
"We don't know what this protein does normally," Edwards said. "But you can take it away from animals, and they still look pretty good. So, if you can reduce this protein, you might help to protect against Parkinson's disease and might reverse some of the pathology in people who have it," he said. "But reducing the level of this protein is not easy to do," he cautioned.
More information
To learn more, vitist the U.S. government's National Institute of Neurological Disorders and Stroke Web site.
