Astrocytes play diverse roles in all facets of brain physiology, suggesting the existence of an extensive reservoir of diverse subpopulations in the adult brain. In fact, Cajal initially described extensive morphological heterogeneity of astrocyte populations in the brain over 100 years ago. Since then, our understanding of the molecular and cellular heterogeneity of astrocytes has remained stagnant, with astrocytes traditionally grouped into two broad categories: fibrous and protoplasmic.
While we were the first to show that patterning oversees the generation of diverse astrocytes in the embryonic spinal cord (Hochstim, et al. Cell 2008), applying these principles to astrocyte populations in the adult brain has remained a challenge because it requires an intimate knowledge of region-specific patterning mechanisms and the associated mouse tools to gain access to these populations. To overcome these limitations we have developed novel tactics and mouse tools that serve as an entry point for unlocking the nature of astrocyte diversity in the brain (Lin, et al. Nature Neuroscience 2017). Using these tools and tactics, we identified several astrocyte subpopulations that are endowed with distinct cellular, molecular, and functional properties in the adult brain.