Research in Parkinson's disease (PD) genetics has been extremely prolific over 
the past decade. More than 13 loci and 9 genes have been identified, but their 
implication in PD is not always certain. Point mutations, duplications and 
triplications in the alpha-synuclein (SNCA) gene cause a rare dominant form of 
PD in familial and sporadic cases. Mutations in the leucine-rich repeat kinase 2 
(LRRK2) gene are a more frequent cause of autosomal dominant PD, particularly in 
certain ethnic groups. Loss-of-function mutations in Parkin, PINK1, DJ-1 and 
ATP13A2 cause autosomal recessive parkinsonism with early-onset. Identification 
of other Mendelian forms of PD will be a main challenge for the next decade. In 
addition, susceptibility variants that contribute to PD have been identified in 
several populations, such as polymorphisms in the SNCA, LRRK2 genes and 
heterozygous mutations in the beta-glucocerebrosidase (GBA) gene. Genome-wide 
associations and re-sequencing projects, together with gene-environment 
interaction studies, are expected to further define the causal role of genetic 
determinants in the pathogenesis of PD, and improve prevention and treatment.