Astrocytes play crucial and diverse roles in neuronal development and function and differentiate into a diverse range of cellular subtypes. Astrocyte subtypes can differ between and within brain regions, suggesting that they are tuned by local cues to support the specific needs of particular neural circuits. How local cues are transduced by astrocytes to drive subtype heterogeneity is poorly understood. In a new study, Wang et al. demonstrate a key role for mouse astrocytic primary cilia in this process.

Primary cilia are non-motile ‘antenna’-like structures that are densely packed with an array of signalling molecules, including molecules involved in the sonic hedgehog signalling (SHH) pathway. Using immunofluorescence staining for ARL13B (a cilia-specific signalling molecule crucial for cilia function), the authors found that most astrocytes in mouse brain have a primary cilium. Conditional knockout of Arl13b (Arl13b KO) in astrocytes resulted in structurally defective astrocyte primary cilia in both cortex and cerebellum. This was accompanied by changes in the transcriptional programmes and morphology associated with different astrocyte subtypes, suggesting that primary cilia are involved in specifying astrocyte subtype transcriptomes.