The non-canonical BMP and Wnt/β-catenin signaling pathways orchestrate early tooth development

Abstract

BMP andWnt signaling pathways play a crucial role in organogenesis, including tooth development. Despite extensive studies, the exact functions, as well as if and how these two pathways act coordinately in regulating early tooth development, remain elusive. In this study, we dissected regulatory functions of BMP and Wnt pathways in early tooth development using a transgenic noggin (Nog) overexpression model (K14Cre;pNog). It exhibits early arrested tooth development, accompanied by reduced cell proliferation and loss of odontogenic fate marker Pitx2 expression in the dental epithelium.We demonstrated that overexpression of Nog disrupted BMP non-canonical activity, which led to a dramatic reduction of cell proliferation rate but did not affect Pitx2 expression. We further identified a novel function of Nog by inhibiting Wnt/β-catenin signaling, causing loss of Pitx2 expression. Co-immunoprecipitation andTOPflash assays revealed direct binding of Nog toWnts to functionally prevent Wnt/β-catenin signaling. In situ PLA andimmunohistochemistryonNogmutants confirmed in vivo interaction between endogenousNog andWntsandmodulationofWnt signalingby Nog in tooth germs. Genetic rescue experiments presented evidence that bothBMPandWnt signaling pathways contribute to cell proliferation regulation in the dentalepithelium,withWnt signaling alsocontrollingthe odontogenic fate. Reactivation of both BMP and Wnt signaling pathways, but not of only one of them, rescued tooth developmental defects inK14Cre;pNogmice, inwhichWnt signaling can be substituted by transgenic activation of Pitx2. Our results reveal the orchestration of non-canonical BMP and Wnt/β-catenin signaling pathways in the regulation of early tooth development.