PAK1 and Parkinson disease: Despite the reduced base of 15 known PD-genes needed for the guilt-by-association predictions we were able to identify from our direct interaction networkSYN1 neighboring three known PD genes, followed by UBE2N and NCAM1 with two and BSN, PAK1, PCHD8, STXBP1, UNC13A and VAMP2 with one such neighbor as novel Parkinson's disease candidate genes.