Gli FHV mice: a novel tool to investigate GLI processing and localization.

GLI proteins (GLI1-3) are the transcriptional effectors of mammalian Hedgehog (HH) signaling. However, studies of GLI function have been hampered by the lack of robust GLI antibodies. To address this, we utilized CRISPR-based gene editing to generate endogenous epitope-tagged Gli alleles for each Gli gene (Gli1FLAG, Gli2HA, Gli3V5). Through breeding, we established a novel mouse model, Gli1FLAG/FLAG;Gli2HA/HA;Gli3V5/V5, referred to as GliFHV. Importantly, GliFHV animals are viable and fertile with no overt phenotypes. Sanger and long-range DNA sequencing confirmed proper editing of each Gli allele, while qPCR and western blot analysis confirmed similar gene expression and protein levels, respectively, between wildtype and GliFHV animals. We utilized these mice to assess GLI localization in the developing limb, finding that all three GLIs localize to primary cilia with distinct distributions. Finally, we generated immortalized GliFHV mouse embryonic fibroblasts (MEFs), demonstrating that these cells are HH-responsive and that GLIs localize to primary cilia and nuclei in a HH-dependent fashion. These animals and cell lines provide a valuable resource for analyses of GLI processing, localization and function throughout embryogenesis, postnatal development, and in adults.