IFNG and Parkinson disease: Fig. 3 shows co-expression of individual genes, showing that on average 39% of IFN-γ genes switch from negative co-expression in normal controls to positive co-expression in Parkinson’s cases (p = 0.0003, Fisher’s trend of permutation tests, Table 1). Again, this result is specific to SNCA, with no other genes showing consistently more IFN-γ co-expression switches. Interferon gamma receptor 1 (IFNGR1) shows the largest SNCA co-expression difference between cases (mean rho = 0.34) and controls (mean rho = −0.38), suggesting a target link in the IFN-γ pathway (Fig. 3, S5 Table).