In vivo genetic labeling of primary cilia in developing astrocytes.

Astrocyte cilia are largely understudied due to the lack of available tools. Astrocyte research advanced with the establishment of Aldh1l1-CreERT2, an inducible Cre line that specifically targets the astrocyte lineage. Here, we develop and compare genetic models that label astrocyte cilia in the developing prefrontal cortex (PFC) using Aldh1l1-CreERT2 and Cre-dependent cilia reporters. We evaluate these models by testing different tamoxifen-induction protocols and quantifying the percentage of astrocytes labeled with the cilia reporters. We show that tamoxifen dosage impacts the expression of cilia reporters in astrocytes. We validate the maximum cilia-labeling efficiency of tamoxifen using constitutively-expressed cilia reporters. The data reveal that only a subset of SOX9- positive astrocytes in the PFC possess cilia throughout development. Our work highlights the utility of Cre-Lox systems to target specific cell types and the importance of carefully validating genetic models.