Differential Expression Patterns of Astrocyte Markers in The Adult Mouse Brain

Astrocytes are the most common glial cells in the mammalian central nervous system. Their diverse structures and functions, along with their critical role as key regulators of brain activity, have recently gained recognition. However, the lack of specific cell markers makes it difficult to identify particular subpopulations. In this study, we examined the distribution of traditional astrocyte markers-glial fibrillary acidic protein (GFAP), SRY-box9 (SOX9), and S100 protein beta (S100β)-in the adult mouse brain. In the cerebral cortex, striatum, and thalamus, most cells did not express GFAP, with limited overlap between GFAP and either SOX9 or S100β. In contrast, the pons-medulla showed a higher rate of co-expression of GFAP and SOX9 compared to the cerebral cortex. In the hippocampus, GFAP was widely expressed and showed significant overlap with SOX9 and S100β. Co-staining of SOX9 and S100β was frequently observed in the cerebral cortex, striatum, thalamus, and midbrain, and S100β-positive cells were more common than SOX9-positive cells. These results reveal regional differences in astrocyte marker expression, highlight the limitations of relying on a single marker like GFAP, and underscore the importance of using multiple markers.