Patterns of Wnt pathway activity in the mouse incisor indicate absence of Wnt/β-catenin signaling in the epithelial stem cells

Authors

  • Marika Suomalainen,

    1. Developmental Biology Programme, Institute of Biotechnology, Viikki Biocenter, University of Helsinki, Finland
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  • Irma Thesleff

    Corresponding author
    1. Developmental Biology Programme, Institute of Biotechnology, Viikki Biocenter, University of Helsinki, Finland
    • Developmental Biology Programme, Institute of Biotechnology, Viikki Biocenter, P.O. Box 56, FIN-00014 University of Helsinki, Finland
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Abstract

The Wnt pathway is crucial for tooth development as shown by dental defects caused by impaired Wnt signaling in mouse and human. We investigated Wnt signaling in continuously growing mouse incisors focusing on epithelial stem cells. Ten Wnt ligands were expressed both in the dental epithelium and mesenchyme, and were associated mainly with odontoblast and ameloblast differentiation. Wnt/β-catenin activity was detected in mesenchyme in BATgal and TOPgal reporter mice while Axin2, also a reporter of Wnt/β-catenin signaling, was expressed additionally in the epithelium. Axin2 was, however, excluded from the epithelial stem cells in the cervical loop. Interestingly, these cells expressed specifically Lgr5, a Wnt target gene and stem cell marker in the intestine, suggesting that Lgr5 is a marker of incisor stem cells but is not regulated by Wnt signaling in the incisor. We conclude that epithelial stem cells in the mouse incisors are not regulated directly by Wnt/β-catenin signaling. Developmental Dynamics 239:364–372, 2010. © 2009 Wiley-Liss, Inc.

Ancillary