Expression of Axin2 Indicates a Role for Canonical Wnt Signaling in Development of the Crown and Root During Pre- and Postnatal Tooth Development

Previously two reporter mice, TOPgal and BATgal, have been used to uncover the spatial patterns of canonical Wnt activity up to the bell stage of tooth development. To further understand the function of this pathway, not only at the early developmental stages of odontogenesis but also in postnatal teeth, we have used Axin2-lacZ mice a direct reporter of canonical Wnt activity. As tooth development progresses, Axin2 expression becomes localized to the primary and secondary enamel knots, and the underlying mesenchyme. In postnatal teeth, Axin2 expression is observed in developing odontoblasts, in the dental pulp and concentrated around the developing roots. Expression is excluded from the ameloblasts and associated with the enamel-free zones at the tip of the molar cusps. This expression identifies new roles for Wnt signaling in defining the regions where enamel will form, and controlling root development at late stages of tooth development. Developmental Dynamics 239:160-167, 2010. (C) 2009 Wiley-Liss, Inc.