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Scientists Identify Gene Variants That Speed Parkinsonís Progression
- May 23 2012
Scientists have identified a possible key to better predicting the course of a person’s Parkinson’s disease (PD). According to new research, motor symptoms progress more quickly in people with Parkinson’s who have certain variations in a gene called SNCA. The study appears in the May 2012 edition of the online journal PLoS One.
Some people with Parkinson’s live for many years without much change in their movement symptoms. Others experience rapid worsening of slowness, stiffness or walking abilities. The gene SNCA, which makes the protein called alpha-synuclein, has long been implicated in Parkinson’s. In fact, scientists discovered 15 years ago that mutations passed from generation to generation can lead to a rare inherited form of PD. The new study is the first to link variations (subtle differences in a gene) in SNCA to disease progression.
Researchers at the University of California, led by Beate Ritz, M.D., Ph.D., studied 233 people with a recent diagnosis of PD with no known cause — none had an inherited form of PD. The researchers used a standard scale, the Unified Parkinson’s Disease Rating Scale (UPDRS), to evaluate study participants’ movement symptoms twice: at the beginning of the study and about five years later. They also drew blood from study participants to isolate DNA and determine the sequence of the SNCA gene.
- Of the 233 study participants, scientists categorized 35 as “fast progressors,” those whose UPDRS scores increased by five points or more per year.
- “Fast progressors” were older at the time of diagnosis compared to “slow progressors;” they also had lower UPDRS motor exam scores at the beginning of the study, yet their UPDRS motor symptom scores increased on average about seven points per year.
- “Fast progressors” were more likely to have carried one or both of two variations in the SNCA gene.
- People carrying the SNCA variant known as the “REP1 263bp” allele, were four times as likely to be “fast progressors.”
- Those individuals who had both the REP1 263bp and the rs356165 ‘G’ allele variants of SNCA were six times as likely to be “fast progressors.”
What Does It Mean?
Uncertainty about how symptoms will develop is frustrating both to people with PD and to their doctors when developing a treatment plan. Certain clinical symptoms — early trouble with walking and balance, for example — have been associated with faster disease progression. But the new study is the first to suggest the possibility of a genetic test for this purpose.
Much like two cars of different paint colors but the same model, gene variations are subtle differences in a gene that rarely affect the function of the protein it makes. However, in the proper context, those variations can affect the body’s response (to a trigger) much like a dark painted car gets hotter in the sun than a light painted car.
However, as in other epidemiological studies, the findings from this research must be confirmed in a larger group. For now, the study adds to the evidence that SNCA is of prime importance in PD, and that drugs targeting the gene may be important in battling Parkinson’s. This study also suggests a way to identify people with PD who will benefit most from early treatment.
PDF Research Advocate Commentary
PDF Research Advocate Diane Cook, of Denver, CO, spoke to ABC News about this story. See her take.
Reference: Ritz, B., Rhodes, S. L., Bordelon, Y., & Bronstein, J. (2012). α-Synuclein Genetic Variants Predict Faster Motor Symptom Progression in Idiopathic Parkinson Disease. (P. Lewis, Ed.) PloS one, 7(5), e36199. doi:10.1371/journal.pone.0036199.t007
Source Date: May 23 2012