The genetics of Parkinson's disease: review of current and emerging candidates

Parkinson's disease (PD) is the second most common neurodegenerative disorder, affecting more than 1% of the population over the age of 65 worldwide. Certain rare forms of the disease are monogenetic, and there is increasing evidence that multiple genetic risk factors are also important for common forms of PD. We have summarized the results from candidate gene and genome-wide association findings in sporadic PD as well as linkage and next-generation sequencing studies of familial PD. To date, 19 genetic loci, PARK1-19, have been reported for rare forms of PD, including autosomal-dominant and autosomal-recessive PD. At 14 of these loci, genes have been identified carrying mutations that are linked to affected family members. These genes have also been shown to constitute candidate genes for idiopathic forms of PD, since they may also carry other mutations that merely increase risk. Multiple genetic factors combine in different ways to increase or decrease risk, and several of these risk factors need to be identified in order to begin unraveling the causative pathways leading to the different forms of PD. In this review, we present current and emerging PD candidate genes to help explain the pathways leading to neurodegeneration.