These differences in the numbers of proliferative cells expressing MCM2 and Sox2 in DBS brains were supported by qPCR results, which revealed higher levels of expression of Sox2 and MCM2 genes in the lining of the third ventricle and peri-lead area, respectively, in PD-DBS tissue compared with normal tissue (Figure 3). This evidence concerns the gene MCM2 and Parkinson disease.