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Genetic Mutations Cause Rare Form of Parkinson’s

By Edward R. Winstead

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A team of American, Spanish, and British scientists has identified a genetic mutation that causes a rare inherited form of Parkinson’s disease in some families. This particular form of the disease occurs late in life and in this respect resembles the more common forms of Parkinson’s that do not run in families and probably involve multiple genes and environmental risk factors.

The researchers made the discovery by searching a region of the genome associated with Parkinson’s disease in four apparently unrelated Basque families. But three of the families, the researchers now know, are descendents of a person who carried the disease-causing mutation.

“At the start we suspected that the families might be related, but there was no genetic evidence,” says Andrew B. Singleton of the National Institute on Aging in Bethesda, Maryland, one of the study’s leaders. “But once we focused in on the region we were able to show that they shared a small chunk of DNA.”

Other research teams had also been looking for a gene in this region. Singleton’s team benefited from the realization that the three families are distantly related because it narrowed the suspect region considerably, leaving them with eleven genes to screen for possible mutations.

The gene they found is now called Park8 and makes a protein the researchers named “dardarin” for the Basque word for tremor, which is a symptom of the progressive and fatal nerve disease.

To confirm their finding independently, the researchers screened the gene Park8 in a British family with a similar form of the disease. Affected members of the family had a different mutation in the same gene.

No test for the mutations is commercially available, but the researchers are willing to refer people who want to be tested to the company that did the testing for the study.

The mutation appeared in about eight percent of the 135 Basque Parkinson’s patients in the study. Singleton does not expect mutations in this gene to account for eight percent of the world’s cases, but he says “it may crop up” in some cases that appear to be sporadic, or to occur for no clear reason.

“This is another gene for Parkinson’s disease and it’s another clue we have about how the disease starts and progresses,” says Singleton. It’s not yet known what Park8 does in the human body, but the researchers are testing theories about the gene in cells and in mice.

Identifying genes associated with rare and often severe forms of common diseases has been a strategy for gaining insights into the biology of these disorders.

“The beauty of this story is that we were able to do this work so quickly because the three groups pooled resources and worked together,” says Singleton.

The study took about six months. The Spanish and British groups are led by Jordi Perez-Tur of the Institut de Biomedicina de Valencia in Spain and Nick W. Wood of the Institute of Neurology in London.

Paisan-Ruiz, C. et al. Cloning of the Gene Containing Mutations that Cause PARK8-Linked Parkinson’s Disease. Published online in Neuron (October 22, 2004).

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