With respect to cortical regions, an increase in OPC (nuclear OLIG1) density was detected in white matter adjacent to the BA32 and BA9 in MDD postmortem as compared to controls, while the density of mature oligodendrocyte (cytoplasmic OLIG1) or MBP level was unchanged, suggesting that changes in OPCs did not directly impact myelin content through the canonical myelinogenic pathway39. Here, OLIG1 is linked to major depressive disorder.