β-Catenin and BMP-2 synergize to promote osteoblast differentiation and new bone formation

✍ Scribed by Gabriel Mbalaviele; Sharmin Sheikh; Joseph P. Stains; Valerie S. Salazar; Su-Li Cheng; Di Chen; Roberto Civitelli

• Book ID: 102875799
• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 764 KB
• Volume: 94
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.20253

✦ Synopsis

Mutations of critical components of the Wnt pathway profoundly affect skeletal development and maintenance, probably via modulation of beta-catenin signaling. We tested the hypothesis that beta-catenin is involved in mesenchymal lineage allocation to osteogenic cells using a beta-catenin mutant with constitutive transcriptional activity (DeltaN151). Although this stable beta-catenin had no effects by itself on osteogenic differentiation of multipotent embryonic cell lines, it synergized with bone morphogenetic protein-2 (BMP-2) resulting in dramatic stimulation of alkaline phosphatase activity, osteocalcin gene expression, and matrix mineralization. Likewise, DeltaN151 and BMP-2 synergistically stimulated new bone formation after subperiosteal injection in mouse calvaria in vivo. Conversely, DeltaN151 prevented adipogenic differentiation from pre-adipocytic or uncommitted mesenchymal cells in vitro. Intriguingly, the synergism with BMP-2 on gene transcription occurred without altering expression of Cbfa1/Runx2, suggesting actions independent or downstream of this osteoblast-specific transcription factor. Thus, beta-catenin directs osteogenic lineage allocation by enhancing mesenchymal cell responsiveness to osteogenic factors, such as BMP-2, in part via Tcf/Lef dependent mechanisms. In vivo, this synergism leads to increased new bone formation.