The interaction between Hertwig＇s epithelial root sheath （HERS） and the adjacent mesenchyme is vitally important in mouse tooth root development. We previously generated odontoblast-specific Ctnnbl （encodingβ-catenin） deletion mice, and demon- strated that odontoblast β-catenin signaling regulates odontoblast proliferation and differentiation. However, the role of odon- toblast β-catenin signaling in regulation of HERS behavior has not been fully investigated. Here, using the same odonto- blast-specific Ctnnbl deletion mice, we found that ablation of β-catenin signaling in odontoblasts led to aberrant HERS for- mation. Mechanistically, odontoblast-specific Ctnnbl deletion resulted in elevated bone morphogenetic protein 7 （Bmp7） ex- pression and reduced expression of noggin andfollistatin, both of which encode extracellular inhibitors of BMPs. Furthermore, the levels of phosphorylated Smadl/5/8 were increased in HERS cells. In vitro tissue culture confirmed that BMP7 treatment disrupted the HERS structure. Taken together, we demonstrated that odontoblast f3-catenin signaling may act through regula- tion of BMP signaling to maintain the integrity of HERS cells.
