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Parkinson's disease gene mutation found.

After announcing last November that they were closing in on a mutant gene that causes Parkinson's disease (SN: 11/30/96, p. 348), scientists have captured their quarry. Unexpectedly, the normal form of the gene encodes a protein implicated in Alzheimer's disease, another neurodegenerative disorder.

While only a small percentage of the millions of people worldwide with Parkinson's disease may have the mutant gene, researchers hope its discovery will provide a clue to the origins of the remaining cases.

"This is a great step forward for Parkinson's disease research that will really unlock the disorder's pathogenesis in the same way that finding [Alzheimer's] mutations unlocked the pathogenesis of that disease," predicts John Hardy of the Mayo Clinic in Jacksonville, Fla.

Parkinson's disease results from the gradual death of brain cells, particularly those that produce the neurotransmitter dopamine. Such cells often control movement, which explains why tremors are a typical symptom of the disease.

Scientists have had few clues to what causes Parkinson's disease, although the brain cells of patients contain mysterious lumps called Lewy bodies. Some investigators believe Lewy bodies trigger cell death, while others suspect they are a by-product of that destruction.

In one Italian and three Greek families plagued by Parkinson's disease, researchers have now traced the origin of the illness to a mutation in the gene for a protein called alpha-synuclein. Mihael H. Polymeropoulos of the National Human Genome Research Institute in Bethesda, Md., and his colleagues report their finding in the June 27 Science.

"The next step is to figure out what the normal function of alpha-synuclein is and whether it aggregates in the Lewy bodies," says study coauthor Lawrence I. Golbe of the Robert Wood Johnson Medical School in Piscataway, N.J. Alpha-synuclein may play a role in synapses, connections that allow brain cells to communicate with one another.

The researchers suggest that mutant forms of alpha-synuclein may aggregate abnormally and thus kill cells or cause other proteins to do so. If so, Parkinson's disease could resemble Alzheimer's, which many investigators now attribute to the accumulation in the brain of a protein fragment called beta-amyloid.

"There are all these nebulous connections [between the two diseases]," says Hardy. For example, relatives of people with Alzheimer's have a higher than average risk of Parkinson's and vice versa. Moreover, the brains of Alzheimer's patients often exhibit Lewy bodies. Finally, researchers discovered several years ago that alpha-synuclein is a major component of the amyloid plaques that develop in Alzheimer's disease.

Investigators note that current therapies for Parkinson's disease address only symptoms. The finding of a mutant gene now "sets the stage to develop research ideas aimed at the cause and not just the symptoms," says Polymeropoulos.
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Title Annotation:mutation in a gene that encodes a protein called alpha-synuclein
Author:Travis, John
Publication:Science News
Article Type:Brief Article
Date:Jun 28, 1997
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