US researchers have identified a genetic risk factor that they say could account for three per cent of the cause of Parkinson's disease (PD). The team, based at the Mayo Clinic in Rochester, Minnesota, has shown that people who inherit a DNA change that increases production of a protein called alpha synuclein have a 50 per cent greater risk of developing the condition. The scientists, who published their findings in the Journal of the American Medical Association, say the study provides evidence that common genetic variants contribute to PD.
People with PD are affected by tremors, stiff muscles and slow movements, caused by a gradual loss of nerve cells in an area of the brain controlling movement. It is not known what triggers this loss, but PD is not normally inherited. However, the illness does occasionally run in families, where the symptoms often appear at a younger age than in non-inherited cases. Researchers think that there are around ten different types of inherited PD, each caused by mutations in different gene. One of these is the alpha synuclein gene (SNCA).
In contrast, most cases of non-inherited PD are thought to be caused by a combination of genetic and non-genetic factors. In the latest study, the researchers analysed genetic and clinical information from 2,692 PD patients and 2,652 healthy controls. They focussed on a particular DNA variation, which, in its longer form, causes over-production of the alpha synuclein protein. The scientists discovered that people with this longer version had a 1.5 times greater risk of developing PD.
Team leader Dr Demetrius Maraganore said that while previous, smaller studies had linked SNCA variations to PD susceptibility, the new research provided 'much-needed evidence' that they contribute to the disease risk in people worldwide. He also said that 'our findings support the development of therapies that reduce alpha-synuclein gene expression. Such therapies have the potential to prevent or delay the onset of Parkinson's disease or to halt or slow its progression'. The scientists stress that further research is needed to confirm the findings, and to investigate how SNCA interacts with other genetic and non-genetic risk factors for PD.