Astrocyte heterogeneity in the neocortex: developmental origins, molecular diversity, and functional implications.

Astrocytes are increasingly recognized as active regulators of brain development and function rather than passive support cells. Advances in single-cell and spatial transcriptomic technologies have revealed extensive molecular and spatial heterogeneity among astrocytes, much of which emerges early during cortical development and defines distinct subtypes. In the neocortex, this diversity is organized along regional and laminar axes reflecting the interplay between intrinsic developmental programs and local environmental cues. Current evidence supports a model in which neocortical astrocyte diversity arises from lineage-encoded programs that are progressively refined by spatial position and neuronal identity. Astrocytes originate from radial glial cells, undergo local postnatal expansion, and mature into spatially organized domains that constrain diversification. Transcriptomic studies identify region- and layer-associated astrocyte subtypes whose molecular programs correlate with specific functions, including synapse formation, circuit modulation, and behavior. Together, these insights establish astrocyte heterogeneity as a fundamental organizing principle of neocortical circuits and a critical dimension for understanding circuit dysfunction in neurological and neurodevelopmental disorders.