Variability in the SNCA gene is linked with a greater susceptibility for Parkinson disease, according to a study in the August 9 issue of JAMA.
Parkinson disease is a common neurological condition associated with increased illness and shortened life expectancy. The origin of Parkinson disease remains elusive, but genetic factors may be important, according to background information in the article. One of the most promising leads in the genetics of Parkinson disease is the potential role of the alpha-synuclein (SNCA) gene. Studies have revealed several SNCA mutations that cause Parkinson disease, but large-scale studies have been lacking.
Demetrius M. Maraganore, M.D., of the Mayo Clinic College of Medicine, Rochester, Minn., and colleagues with the Genetic Epidemiology of Parkinson's Disease (GEO-PD) Consortium, conducted a study to examine several issues, including whether allele-length (one of a number of alternative forms of the same gene occupying a given position on a chromosome) variability in the dinucleotide repeat sequence (REP1) of the SNCA gene is associated with Parkinson disease susceptibility. The researchers performed a collaborative analysis of individual-level data on SNCA REP1 and flanking markers in patients with Parkinson disease and controls. Study site recruitment, data collection, and analyses were performed between April 4, 2004, and December 31, 2005. Eleven participating sites of a global genetics consortium provided clinical data for 2,692 cases and 2,652 controls.
The researchers found that genotypes defined by the 263 base-pair allele were associated with Parkinson disease.
"Our study demonstrates that the SNCA gene is not only a rare cause of autosomal dominant Parkinson disease in some families, but also a susceptibility gene for Parkinson disease at the population level. Based on our results, we estimate that REP1 locus variability may explain approximately 3 percent of the risk in the general population. This is in the same range as the population effect of other common variants implicated in Parkinson disease. The additive effects of these and other common gene variants may ultimately account for a substantial fraction of the susceptibility to Parkinson disease," the authors write. (JAMA. 2006;296:661-670. Available pre-embargo to the media at www.jamamedia.org)
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