Synergistic Functions Of Gli2 And Gli3 In Tooth Root Morphogenesis.

Hedgehog signaling pathway has been implicated as a pivotal transduction center in orchestrating tooth morphogenesis. Gli2 and Gli3, downstream transcriptional factors of Hedgehog signaling, exhibit synergistic functions in directing embryo development. However, whether tooth root pattern fits this paradigm has not been comprehensively investigated. We mapped the dynamic expression pattern of Gli2 and Gli3 during tooth root development using RNA Scope. To study the combinatorial roles and compartment-specific functions of Gli2 and Gli3, we generated transgenic mouse models in which Gli2 or Gli3 were deleted alone or simultaneously in Gli1+ progenitor cells and dental epithelium. Micro-CT, histological and immunofluorescence staining were performed to examine proliferation and differentiation of root progenitor cells. RNA-seq, ChIP analysis and in vivo rescued experiments were conducted to identify the downstream molecular mechanism. The results showed extensive expression of Gli2 and Gli3 in epithelium and mesenchyme of tooth germ, with Gli3 exhibiting a robust abundance in dental mesenchyme. The conditional mouse models demonstrated that loss of Gli3 in Gli1+ progenitor cells caused shortened roots while Gli2 ablation didn’t cause obvious tooth root anomaly. Importantly, concurrent loss of Gli2 and Gli3 in Gli1+ progenitor cells resulted in more severe tooth root dysplasia with compromised dentin formation, periodontal ligament differentiation and alveolar bone mineralization, suggesting Gli2 and Gli3 in Gli1+ progenitor cells synergistically regulate toot root morphogenesis. Our study endowed that Gli2 and Gli3 synergistically mediate tooth root development through regulating proliferation and differentiation of Gli1+ root progenitor cells.