Two new studies strongly suggest that a mutation in a recently discovered gene is the most common genetic cause of Parkinson's disease identified to date. The discovery by an international research team provides fresh evidence that genetics may contribute to the development of some cases of Parkinson's disease. The findings could lead to the development of a genetic test to detect the mutation in individuals at risk. The research team includes investigators at the National Institute on Aging (NIA) and scientists supported by the National Institute of Neurological Disorders and Stroke (NINDS).
Parkinson's disease,
which affects at least 500,000 Americans, is a progressive neurologic
disorder that is caused by the degeneration of nerve cells in the
portion of the brain that controls movement. Scientists have long
suspected genetics plays a role in the onset of the disease. In these
studies, the investigators found that a mutation in the gene LRRK2
appears to occur in at least one of every 60 people who have the
disease. Overall, the mutation could be responsible for up to 5 percent
of Parkinson's disease in people with a family history of the disorder
and may account for 1½ to 2 percent of cases in individuals who do not
have a family history of the disease. The researchers found a mutation
in one copy of the gene can lead to the disease. The findings were
published online by Lancet at 6:30 p.m. ET on January 17, 2004. Copies
of the studies will be made available to the media on January 17. To
request copies, journalists should email pressoffice@lancet.com.
"Among the forms of Parkinson's disease that are genetic in origin,
this gene mutation causes more cases of Parkinson's disease than any
other gene discovered to date," says Andrew Singleton, Ph.D., chief of
the Molecular Genetics Unit in the NIA's Laboratory of Neurogenetics.
"Knowing that this mutation is not only important in familial forms of
disease, but in typical sporadic disease, where there is no st
rong
family history, could lead to earlier detection of Parkinson's disease.
Further study of how this gene works also might help scientists
identify new treatments."
In addition to Dr. Singleton, the collaborative work was spearheaded by
William C. Nichols, Ph.D., of Cincinnati Children's Hospital, Tatiana
Foroud, Ph.D., of Indiana University Medical Center, Indianapolis, and
Nicholas W. Wood, M.D., of the Institute of Neurology in London. The
NIA and the NINDS are part of the National Institutes of Health (NIH)
at the U.S. Department of Health and Human Services.
Singleton and his colleagues recently discovered LRRK2, a gene that
encodes a protein named dardarin by the researchers from the Basque
word dardara, which means tremor, a major symptom of Parkinson's
disease. It was isolated on a region of chromosome 12 called PARK8 by
investigators who studied five families with a history of Parkinson's
disease who lived in the Basque region of Spain and in England.
In these new studies, the researchers sought to determine the
prevalence of the genetic mutation in other families and individuals
being studied by the Parkinson's Study Group with NINDS support. In an
analysis of 358 families with a history of Parkinson's disease, for
instance, the investigators found that 34 of the 767 people who had
inherited the disease had at least one copy of the mutated gene.
Similarly, the team detected one copy of the mutation in 8 of 482
people with Parkinson's disease, but who didn't report a family history
of the disease. The Parkinson's Study Group is a non-profit,
cooperative group of Parkinson's disease experts from 59 medical
centers in the United States and Canada who are dedicated to improving
treatment for people affected by Parkinson's disease.
"NINDS is pleased to have supported the collection of this large group
of families and sibling pairs, which is proving to be an invaluable
resource for these studies," says Diane Murphy, Ph.D., a program
director at NINDS. "Because
the prevalence of this mutation is 5
percent in families with a history of the disease and it is relatively
common even among those without a family history, it's possible that
detecting this mutation will help identify people at increased risk for
Parkinson's disease."
About 50,000 Americans are diagnosed with Parkinson's disease each
year. The disease occurs when certain nerve cells die or become
impaired and can no longer produce dopamine, a brain signaling chemical
(neurotransmitter). Without it, individuals can develop tremor or
trembling in hands, arms, legs, jaw, and face; rigidity or stiffness of
the limbs and trunk; bradykinesia, or slowness of movement; and
postural instability or impaired balance and coordination. Patients may
also have difficulty walking, talking, or completing other simple
tasks. The disease is both chronic and progressive. Incidence of the
disease increases with age, with an average onset at about 60 years.
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Source:Eurekalert
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