"Like the discovery of the BRCA1 and BRCA2 gene mutations for breast cancer, this finding will directly affect the way Parkinson's disease is diagnosed in Ashkenazi Jews," says Dr. Susan B. Bressman, senior investigator of the report, who also is Chairperson of Neurology at Beth Israel, as well as Professor and Vice Chair of Neurology at Einstein. "It also emphasizes the benefit of focusing genetic studies in a specific ethnic group, even with regard to a disease not thought to be primarily genetic in origin,"
"Up until now, genetic counseling for Parkinson's disease hasn't really been considered," adds study co-author Dr. Laurie J. Ozelius, Associate Professor of Molecular Genetics at Einstein. "Our finding should bring genetic counseling for Parkinson's disease to the forefront along with genetic testing for early detection of Parkinson's disease."
The researchers focused on a gene called LRRK2, which is mutated in about 1% of late-onset non-familial cases of Parkinson's disease in those patients who are primarily of European ancestry.
Their study involved 120 unrelated Ashkenazi Jewish Parkinson's disease patients who had been seen as outpatients at Beth Israel's neurology department and screened for the gene. For comparison, a control group of 317 Ashenazi Jews who did not have Parkinson's disease was also studied. DNA was extracted from white blood cells or cheek cells of all the study participants and analyzed for mutations.
The G2019S mutation--the most common of several possible LRRK2 mutations--was detected in 18.3 percent (22 out of 120) of the Ashkenazi Jewish Parkinson's patients compared with only 1.3 percent (4 out of 317) of control patients.
The mutation's role was even more dramatic when the 120 Parkinson's disease patients were divided into those (37) with a family history of the disease (defined as having at least one affected first, second, or third degree relative) and those (83) with no family history. The G2019S mutation was found in 29.7 percent (11/37) of the familial Parkinson's cases but also in 13.3 percent (11/83) of so-called sporadic or nonfamilial cases. The frequency of this mutation among Ashkenazi Parkinson's patients was 15 to 20 times higher than has been reported among patients of European ancestry in general.
In addition to Ashkenazi Jews, the researchers note that a group of North Africans of Arab descent have been found to have a high frequency of this same gene mutation as a cause of Parkinson's disease. The two groups appear to share the same origin or founder, suggesting a probable Middle Eastern origin for this mutation.
Funding for the study was provided by the Edwin and Caroline Levy Foundation, the Michael J. Fox Foundation for Parkinson's Research, the Thomas Hartman Foundation for Parkinson's Research Inc. and the National Institutes of Health.
In addition to Drs. Bressman and Ozelius, authors on the paper included: Geetha Senthil, Ph.D., Rachel Saunders-Pullman, M.D. M.P.H., Erin Ohmann,B.S., Amanda Deligtisch, M.D., Michele Tagliati, M.D., Ann L. Hunt, D.O., Christine Klein, M.D., Brian Henick, Susan M. Hailpern, M.S., M.P.H., Richard B. Lipton, M.D., Jeannie Soto-Valencia, B.A. and Neil Risch, Ph.D.
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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