Wnt Signaling from Gli1-Expressing Apical Stem/Progenitor Cells Is Essential for the Coordination of Tooth Root Development

Loss of Wnt production in Gli1+ apical stem/progenitor cells led to loss of Axin2 at the root apex, mis-regulation of SOX9, loss of BMP and Hh signaling, and truncation of root development. In the absence of Wnt signals, the root epithelium lost its integrity and epithelial identity.