NRG1 and major depressive disorder: Notably, we ascertained that out of the ten identified MDD-related biomarkers, six biomarkers (CLEC12B, HP, LCN2, OLFM4, SERPING1, and THBS1) were related to a specific subset of brain regions, however, CEACAM8, DEFA4, NRG1, TCN1 do not show a distinct differential expression on the brain areas of healthy cases.