Parkinson's disease (PD) can be divided into familial (Mendelian) and sporadic forms. A number of causal genes have been discovered for the Mendelian form, which constitutes 10-20% of the total cases. Genome-wide association studies have successfully uncovered a number of susceptibility loci for sporadic cases but those only explain a small fraction (6-7%) of PD heritability. It has been observed that some genes that confer susceptibility to PD through common risk variants also contain rare causing mutations for the Mendelian forms of the disease. These results suggest a possible functional link between Mendelian and sporadic PD and led us to investigate the role that rare and low-frequency variants could have on the sporadic form. Through a targeting approach, we have resequenced at 49× coverage the exons and regulatory regions of 38 genes (including Mendelian and susceptibility PD genes) in 249 sporadic PD patients and 145 unrelated controls of European origin. Unlike susceptibility genes, Mendelian genes show a clear general enrichment of rare functional variants in PD cases, observed directly as well as with Tajima's D statistic and several collapsing methods. Our f

This work was supported by Ministerio de Ciencia e Innovación, Spain (SAF2011-29239 to E.B. and BFU2012-38236 to A.N.), by Direcció General de Recerca, Generalitat de Catalunya (2009SGR-1101 and 2014SGR-866), by the Spanish National Institute of Bioinfomatics of the Instituto de Salud Carlos III (PT13/0001/0026), CIBERNED and by FEDER (Fondo Europeo de Desarrollo Regional)/FSE (Fondo Social Europeo).