Microglial Gene Expression Alterations in the Brains of Patients with Psychiatric Disorders

As recent studies have shown that microglia play a key role in inflammation and immunological challenges as well as have broader roles in synaptic modulation in the brain, studies on psychiatric disorders have increasingly focused on microglia. Microglial abnormalities have consistently been observed in psychiatric postmortem brain studies, including altered microglial activation and changes in the protein and mRNA expression levels of microglial marker molecules, such as major histocompatibility complex, class II, DR (HLA-DR), complement receptor type 3 (CD11b), ionized calcium binding adaptor molecule 1 (IBA-1), macrosialin (CD68) and glucose transporter type 5 (GLUT5). Microglial abnormalities have also been observed in positron emission tomography (PET) studies. Recent advances in omics-based microglial gene expression profiling of psychiatric brains may elucidate microglial involvement in the pathogeneses of psychiatric disorders. In the present paper, we review the current status of research on expression profiling of microglia-relevant molecules in psychiatric postmortem and imaging studies and we discuss future research directions.