Age-dependent glial heterogeneity and traumatic injury responses in a vertebrate brain structure.

The progression of traumatic brain injury (TBI) pathology is significantly influenced by age and involves a complex interplay of glial cells. However, the influence of age on the glial dynamics and their TBI responses remains mostly unexplored. Here, we obtain a comprehensive single-cell transcriptome atlas of three major glial types under the physiological and TBI conditions across four post-embryonic life stages in the zebrafish midbrain optic tectum. We identify a library of glial subtypes and states with specific age-dependent patterns that respond distinctly to TBI. Combining the glial interactome analysis and CRISPR-Cas9-mediated gene disruption, we reveal the essential roles of dla-notch3 and cxcl12a-cxcr4b interactions in the early-larval-stage-specific unresponsiveness of radial astrocytes to TBI and the TBI-induced age-independent recruitment of microglia to injury sites, respectively. Overall, our findings provide the molecular and cellular framework of TBI-induced age-related glial dynamics in vertebrate brains.