The overlap of our RNA-seq data with results from earlier microarray studies on postmortem PD and control SN confirms the importance of the degeneration of dopaminergic neurons in this brain region, since 10 out of the 12 DEGs that were found in at least half of the studies are associated with dopaminergic neurons or PD (ALDH1A1, DDC, DLK1, DRD2, GAP43, KCNJ6, SLC18A2, SLC6A3, SV2C and TH). This evidence concerns the gene DLK1 and Parkinson disease.