Study finds genes not environment behind Parkinson's
An EU-wide study has found five new genetic variants for Parkinson's disease. The research was funded in part by the NEURON ('Network of European funding for neuroscience research') initiative, a Coordinated Action funded under the ERA-NET scheme of the EU's Sixth Framework Programme (FP6) to the tune of EUR 2.7 million. Participating in NEURON were experts from Austria, Finland, France, Germany, Israel, Italy, Luxembourg, Poland, Romania, Spain, Sweden and the UK. The research was recently published in The Lancet journal.
Most researchers thought that environmental factors were wholly responsible for Parkinson's disease. Since 2007, however, scientists have identified six genetic variants or 'loci' that increase the risk of developing the condition. Scientists have now found a further five loci, leading them to suggest that genetic, rather than environmental factors as previously believed, may be the key cause of the disease.
'This study provides evidence that common genetic variation plays an important part in the cause of Parkinson's disease,' the scientists say. 'We have confirmed a strong genetic component to Parkinson's disease, which, until recently, was thought to be completely caused by environmental factors.' They concluded that 'the identification of additional common and rare risk variants for Parkinson's disease will probably revise our estimate of the genetic component of disease upward'.
The research team came to these conclusions after conducting what they described as the largest genetic analysis of Parkinson's disease ever undertaken. They study involved a meta-analysis of five genome-wide association studies (GWAS) from the US and Europe covering some 7.7 million possible genetic variants. Common variants previously identified in the MAPT (Microtubule Associated Protein Tau) and SNCA (synuclein, alpha (non A4 component of amyloid precursor)) genes were shown to contribute the majority of the estimated genetic risk identified.
The researchers found that the 20% of patients with the highest number of risk variants at the 11 identified loci were 2.5 times more likely to develop Parkinson's than the 20% possessing the least number of genetic risk factors. Although this suggests substantively more genetic risk than previous studies, the authors cautioned that these risk profiles were not yet of clinical validity. However, they said these data highlighted new genes on which to focus future research, and described their findings as a launching point into further investigations into the pathophysiology of this debilitating condition.
In a linked comment, Drs Christine Klein and Andreas Ziegler from the University of Lübeck in Germany, say: 'Clinically, the most burning question is whether these findings will bear on patients' care.' They said there was 'no simple answer' to this question and urged caution on the potential for screening for possible cases of Parkinson's based on this study.
'Although genetic testing for monogenic Parkinson's disease might be useful to minimise further work-up, clarify treatment approaches, and assist with future family planning, the clinical validity of risk SNPs [single-nucleotide polymorphisms] is currently questionable at best,' they note.
However, they agreed that 'the consortium's confirmation and discovery of potentially causal SNPs for the disease hold great promise for establishing causal hypotheses', adding that 'this landmark study also serves another important purpose in that it provides a comprehensive stock-check on where we stand on our way towards clinical use of GWAS data in Parkinson's disease'.
Drs Klein and Ziegler conclude: 'While being cautious to avoid overstating the value of association findings in terms of personalised medicine, with this confluence of new research leads and impressive technical advances there is good reason for optimism that these advances will be translated into direct benefits for our patients.'