GPNMB and Parkinson disease: In addition to its connection to PD, we present new evidence showing that serum GPNMB shares a causal variant with GPNMB gene expression in both whole blood (CLPP4 = 0.79) and brain tissue (basal ganglia CLPP4 = 0.70; cortex CLPP4 = 0.74; anterior cingulate cortex CLPP4 = 0.83).