SNCA and Parkinson disease: Two lines of evidence, (1) the identification of the CPLX1 gene variant rs10794536 that is associated with PD risk in a relatively small case-control study, and (2) the demonstration that genetic ablation of Cplx1 in mouse brain leads to an elevation of SNCA levels that is comparable to PARK4, both argue that complexin 1 also has a role as risk factor in PD, not only a role as biomarker.