To better characterize the pool of GPR17-expressing (GPR17+) cells, we performed immunohistochemical analysis focusing on the ventral lumbar spinal cord, that is the region most affected by ALS pathology [33,34,35], of both wtSOD1 and SOD1G93A mice, in order to detect possible regional differences between WM and GM areas. The gene discussed is GPR17; the disease is amyotrophic lateral sclerosis.