Global gene expression following correction for cell composition (for microglia, astrocytes, and neurons, see Materials and Methods) indicated that the differences in the SN of PD individuals included genes associated with PD (e.g., SNCA, TH, DNAJC6, SYNJ1, GBA, DNAJC6, and SLC6A3) (corrected P = 0.00048), synapse (corrected P = 2.06E‐05) and neurodegeneration (corrected P = 0.0017; Miller et al, 2004; Zhang et al, 2005; Moran et al, 2006; Simunovic et al, 2009; Lewis & Cookson, 2012). Here, GBA1 is linked to Parkinson disease.