<i>Pitx2-Sox2-Lef1</i> interactions specify progenitor oral/dental epithelial cell signaling centers

Abstract

Epithelial signaling centers control epithelial invagination and organ development, but how these centers are specified remains unclear. We report that <i>Pitx2</i> (the first transcriptional marker for tooth development) controls the embryonic formation and patterning of epithelial signaling centers during incisor development. We demonstrate using <i>Krt14^Cre</i> /<i>Pitx2^flox/flox</i> (<i>Pitx2^cKO</i> ) and <i>Rosa26^CreERT/Pitx2^flox/flox</i> mice that loss of <i>Pitx2</i> delays epithelial invagination, and decreases progenitor cell proliferation and dental epithelium cell differentiation. Developmentally, <i>Pitx2</i> regulates formation of the Sox2⁺ labial cervical loop (LaCL) stem cell niche in concert with two signaling centers: the initiation knot and enamel knot. The loss of <i>Pitx2</i> disrupted the patterning of these two signaling centers, resulting in tooth arrest at E14.5. Mechanistically, Pitx2 transcriptional activity and DNA binding is inhibited by Sox2, and this interaction controls gene expression in specific Sox2 and Pitx2 co-expression progenitor cell domains. We demonstrate new transcriptional mechanisms regulating signaling centers by <i>Pitx2</i>, <i>Sox2</i>, <i>Lef1</i> and <i>Irx1</i>.