It's official, the Ashkenazi Jews and Arabs Share Same Gene Mutation -- from two separate sources the study is confirmed
- From: "Jason P" <jaspetr@xxxxxxxxxxxx>
- Date: 26 Jan 2006 06:41:26 -0800
January 26, 2006
LA Times -- Science
THE NATION
Genetic Link to Parkinson's Disease Is Detected in 2 Ethnic Groups,
Scientists say a mutation causes 18% of cases in Ashkenazi Jews and 37%
in North African Arabs.
By Thomas H. Maugh II, Times Staff Writer
A recently discovered mutant gene causes 18% of Parkinson's disease
cases in Ashkenazi Jews and 37% in North African Arabs - a surprising
finding because genetics had been thought to play only a small role in
the disorder.
The discovery will allow genetic counseling and early diagnosis of the
disease in the affected groups, said Dr. Susan B. Bressman, a
neurologist at the Albert Einstein College of Medicine in New York and
the leader of one of two studies on the subject published today in the
New England Journal of Medicine.
Although there is no known way to prevent development of the brain
disorder, which affects at least half a million Americans, early
diagnosis would allow expanded use of newer drugs that delay its onset.
The fact that the gene plays such a large role in the two ethnic groups
suggests that other mutated genes - perhaps different variants of
this one - cause the disease in other ethnic groups.
The mutant form of the gene LRRK2 was linked to Parkinson's in late
2004 by two groups, a joint U.S.-Spanish team and one at the University
of Tubingen in Germany.
It was identified in members of a large family in the Basque region of
Spain, and the protein it produces was given the name Dardarin, Basque
for "tremor."
It was the third gene linked to the disorder. The two other genes
produce unusual forms of Parkinson's disease that have an earlier onset
and a more aggressive course.
LRRK2 produces symptoms very similar to those observed in the majority
of Parkinson's patients, although it is found in only 2% to 3% of
people with the disease.
Bressman and her colleagues studied DNA from 120 Ashkenazi Jews with
Parkinson's disease and 317 healthy Ashkenazi Jews. Ashkenazim, or Jews
of Eastern European descent, account for an estimated 80% of Jews
worldwide.
The researchers found that 18% of those with Parkinson's carried the
specific mutation, compared with about 1% of the healthy subjects -
meaning that the presence of the gene in Ashkenazim increased the risk
of developing Parkinson's 15 to 20 times. Among patients with a family
history of the disorder, 30% carried the mutant gene.
In a similar study led by Dr. Alexis Brice and geneticist Suzanne
Lesage of the French research institute INSERM, the team found that
about 30% of North Africans with Parkinson's carried the specific
mutation, compared with 3% of the healthy subjects. Among North African
Arabs with the disease, the incidence of the gene rose to 37%.
"The importance of genetics [in Parkinson's disease] has been disputed
for years and years," Bressman said. Most people thought it was
primarily environmental in origin, perhaps from pesticides or some
other toxin.
Now, in at least two ethnic groups, genetics "is very important," she
said.
Dr. Neil Risch of UC San Francisco, who participated in Bressman's
study, said the mutation probably arose in a common ancestor of the
Jews and Arabs several thousand years ago. The mutation, he added, is
probably important in multiple Middle Eastern populations.
Copyright 2006 Los Angeles Times
-- -- -- --
MedPage Today
By Michael Smith
Staff Writer
Reviewed by Rubeen K. Israni, M.D., Fellow, Renal-Electrolyte and
Hypertension Division, University of Pennsylvania School of Medicine
January 25, 2006
NEW YORK, Jan. 25 - A large proportion of Ashkenazi Jews and North
African Arabs with Parkinson's disease carry the same single gene
mutation, according to two studies.
The mutation -- apparently derived from a single "founder"
individual several centuries ago -- was found in 18.3% of a cohort of
120 Ashkenazi Jews treated for Parkinson's at the Albert Einstein
College of Medicine and Beth Israel Medical Center here.
The same mutation was found in 39% of a cohort of 76 Arabs with the
disease, French researcher said. Both studies were published as letters
in the Jan. 26 issue of the New England Journal of Medicine.
The single-base-pair alteration, dubbed G2019S, is found on exon 41 of
the leucine-rich repeat kinase 2 (LRRK2), according to Laurie Ozelius,
Ph.D., of the Albert Einstein College of Medicine and lead author of
the paper describing the Jewish cohort.
Overall, Dr. Ozelius said, 22 of the 120 Parkinson's patients carried
the mutation, but only four of 317 controls with the same ethnic
background carried the mutation. Carrying the mutation gave an odds
ratio for disease of 17.6, with a 95% confidence interval ranging from
5.9 to 52.2.
Also, the mutation was found in 11 of 37 (29.7%) of patients with a
familial pattern of disease, and 11 of 83 (13.3%) patients with
apparently sporadic disease.
One implication of the finding, Dr. Ozelius said in an interview, is
that many patients thought of as having sporadic disease probably have
familial -- but unknown or unrecognized -- connections.
"What this is telling us is that there is this group of people who
supposedly have sporadic Parkinson's, but actually have a genetic
form of the disease," she said.
The gene mutation has been shown to be due to a single founder in
European populations, where it is carried by about 5% of familial
patients and 1% of sporadic patients -- rates much lower than those
found by the New York group, Dr. Ozelius said.
However, genetic markers in and surrounding the altered gene in the
Jewish cohort show that it is identical to the gene found in the
European studies. "The mutation is the same mutation as that in the
European population - it's due to the same founder," Dr. Ozelius
said.
The New York results, combined with the Arab study, which also found
the same genetic pattern, imply that the gene mutation has its origins
in the Middle East. Dr. Ozelius said some of her colleagues are now
trying to estimate when it first appeared.
In the other study, researchers from the French Parkinson's Disease
Study Group examined a cohort of 104 Parkinson's patients in North
Africa, including 76 Arabs, 18 Europeans born in North Africa, six
Sephardic Jews, and four black Africans, as well as a cohort of 151
healthy Arab controls.
The study showed that 31 of the 104 patients (30%) carried the
mutation, according to Suzanne Lesage, Ph.D., of the French national
institute for health and medical research's unit 679 in Paris, and
lead author of the study.
But all but one of the carriers was Arab, Dr. Lesage and colleagues
found, and the other carrier was a Sephardic Jew.
Among the 76 Arab patients, the researchers found, 10 of the 27
familial cases (37%) carried the mutation and 20 of the 49 sporadic
cases (41%) carried the mutation. Two of the controls were also found
to have the mutation. Carrying the mutation gave an odds ratio for
disease of 48.6 (95% CI 11.2 to 211) in Arab patients.
Both groups of researchers noted that the finding will have
implications for genetic testing and counseling, although the issue is
fraught with difficulty since there is no cure for the disease.
But Dr. Ozelius said the findings may also make it possible to tease
out some of the earliest signs of Parkinson's disease, because
genetic screening would find carriers of the mutated gene long before
they develop symptoms.
"This really opens up our ability to look at a homogenous population
-- everyone with the same mutation -- and look at pre-clinical
things," she said.
Primary source: New England Journal Of Medicine
Source reference:
Ozelius LJ et al. LRRK2 G2019S as a Cause of Parkinson's Disease in
Ashkenazi Jews. N Engl J Med 2006;354:424-25.
Additional source: New England Journal Of Medicine
Source reference:
Lesage S et al. LRRK2 G2019S as a Cause of Parkinson's Disease in
North African Arabs. N Engl J Med 2006;354:422-23
© 2004-6 MedPage Today, LLC. All Rights Reserved.
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