highly significantp = 1.92 × 10 –9
As expected given the mesodermal origin of microglial cells 40 , we found highly significant associations between microglial cell-specific genes with the top 25% values of dN/dS and immune system-related GOs (χ 2 = 36.048, p = 1.92 × 10 –9 ), in agreement with previous reports of enrichment of immune system-related genes in microglial cells 41 .