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Novel links among Wnt and TGF-beta signaling and Runx2.

Authors
  • McCarthy, Thomas L1
  • Centrella, Michael
  • 1 Department of Surgery, Yale University School of Medicine, 333 Cedar Street, MS 208041, New Haven, Connecticut 06520, USA. [email protected]
Type
Published Article
Journal
Molecular Endocrinology
Publisher
The Endocrine Society
Publication Date
Mar 01, 2010
Volume
24
Issue
3
Pages
587–597
Identifiers
DOI: 10.1210/me.2009-0379
PMID: 20093419
Source
Medline
Language
English
License
Unknown

Abstract

Osteoblasts exhibit complex Wnt-induced effects that increase T cell factor (TCF)/lymphoid enhancing factor-dependent transcription in parallel with beta-catenin stabilization and nuclear factor binding to TCF response element DNA. Here we show that Wnt-dependent gene expression increases during the early phase of osteoblast differentiation in vitro, is enhanced by prostaglandin E(2) activation of transcription factor Runx2 (runt homology domain transcription factor 2), and is specifically suppressed in Runx2 antisense-depleted osteoblasts. Moreover, Wnt pathway induction increases expression of the Runx2-sensitive gene, TGF-beta type I receptor, without increasing nuclear Runx2 levels or Runx2 binding to DNA. Rather, despite an increase in beta-catenin levels, Wnt pathway induction enhances Runx2 transcriptional potential in a beta-catenin-independent way. Runx2 functionally associates with TCF-4 that lacks a beta-catenin-binding domain and is more fully activated in response to both prostaglandin E(2) and Wnt pathway induction. Wnt pathway induction increases TGF-beta type I receptor expression, yet regulates, both positively and negatively, TGF-beta signaling. Furthermore, TGF-beta signaling enhances TCF-4 and lymphoid enhancing factor-1 mRNA expression and increases TCF-4 transcriptional activity. Therefore, we propose that cross talk between the Wnt and TGF-beta pathways, which converge on Runx2, both promotes and attenuates individual aspects of osteoblast maturation.

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