PARKINSON'S DISEASE Researchers identify genetic mutation

Should people be offered genetic tests?
WASHINGTON POST
Researchers said Wednesday they have identified a single genetic mutation that accounts for more than 20 percent of all cases of Parkinson's disease in Arabs, North Africans and Jews, a big surprise for a major disease in which genetics was thought to play a relatively minor role.
Although the mutation is rare in people with ethnic roots outside the Middle East, its discovery raises the prospect that undiscovered mutations may be major causes of Parkinson's in other groups.
"Genetics are going to be a lot more important in Parkinson's than people have appreciated," said study leader Susan Bressman, a neurologist at Albert Einstein College of Medicine and Beth Israel Medical Center in New York.
The finding -- described in a pair of reports in today's New England Journal of Medicine -- could help reveal at last the mysterious underpinnings of Parkinson's, which causes tremors, rigidity and mental decline, and is growing more common as the population ages.
But it also raises the delicate question of whether some people should be offered tests to see if they harbor the predisposing glitch -- a tough call since there is no known way to prevent the disease.
Ethnic connection
In this era of Arab-Israeli tensions, the discovery of shared genetic flaws might even serve as a small olive branch, scientists said.
"Yasser Arafat once said we are all cousins. Well, it's the truth," said Neil Risch, director of the University of California at San Francisco's Institute of Human Genetics.
Parkinson's affects at least 500,000 Americans and has no cure, though drugs can slow its progression. Studies have long hinted that most cases arise from a combination of environmental factors -- almost none of which have been identified, though some have implicated pesticides.
The new work focuses on a gene called LRRK2 (for leucine-rich repeat kinase 2), which carries the instructions that brain cells need to make a protein called dardarin.
The gene has been under scrutiny since 2004, when a rare mutation within it was linked to Parkinson's in a handful of families in the Basque region of Spain and France. "Dardarin" is a form of the Basque word for tremor.
In the new work, researchers studied a different mutation in the same gene.
Like all proteins, dardarin is a string of amino acids -- 2,527 of them in all. In people with the newly studied mutation, cells make an abnormal version of dardarin in which amino acid number 2,019 is glycine instead of serine.