Although the cause(s) of Parkinson’s is currently unknown, most researchers believe that multiple factors play a contributory role in causing Parkinson’s and it is likely to be caused by a combination of both genetic and environmental factors. We know that genetics play an important role in the development of Parkinson’s. Nine genes are associated with the rare familial/inherited form of Parkinson’s. One of them, PARK5, is responsible for producing the protein known as UCH-L1, which is involved in the cell machinery that breaks down unwanted proteins in the nervous system. This gene was originally identified by this group of researchers in 1987 and has been linked with susceptibility to familial Parkinson’s. There may also be genetic factors that make people more susceptible to the non-inherited form of Parkinson’s. The genetic basis of Parkinson’s is therefore complex.