Between PD and Control conditions, differential gene expression analysis identifies genes associated with GO/KEGG terms including RNA polymerase complex function (e.g., GTF2F2, POLR3G, GTF2H3 and CCNH), serine/threonine phosphatase activity (e.g., PPP2R2B, PPP4R2, PPP2R2C and PPP3CA), histone acetyltransferase complex function (e.g., CREBBP, EP300, JADE2 and TAF4), protein ubiquitination (e.g., ANAPC16, FBXW8, SKP2 and KLHL21) and lysosomal activity (e.g., DMXL1, ARSB and SORT1) (Fig. 5G; Supplementary Table 8). The gene discussed is POLR3G; the disease is Parkinson disease.