GPNMB and Parkinson disease: Notably, we observed significant hypomethylation of the Snca and Gpnmb genes in the A30P mice given DSS, but not in the wild-type mice given DSS (q < 0.05, robust linear regression; Supplementary Fig. 12a and Supplementary Fig. 12b); these genes were both epigenetically perturbed in the PD appendix (Fig. 1a).