title: Wnt-mediated regulation of chondrocyte maturation: modulation by TGF-beta.
abstract: Wnt proteins are expressed during limb morphogenesis, yet their role and mechanism of action remains unclear during long bone growth. Wnt expression, effects and modulation of signaling events by BMP and transforming growth factor-beta (TGF-beta) were evaluated in chick embryonic chondrocytes. Chondrocyte cell cultures underwent spontaneous maturation with increased expression of colX and this was associated with an increase in the expression of multiple Wnts, including Wnt 4, 5a, 8c, and 9a. Both parathyroid hormone related peptide (PTHrP) and TGF-beta inhibited colX, but had disparate effects on Wnt expression. While TGF-beta strongly inhibited all Wnts, PTHrP did not inhibit either Wnt8c or Wnt9a and had lesser effects on the expression of the other Wnts. BMP-2 induced colX expression, and also markedly increased Wnt8c expression. Overexpression of beta-catenin and/or T cell factor (TCF)-4 also induced the type X collagen promoter. Overexpression of Wnt8c induced maturation, as did overexpression of beta-catenin. The Wnt8c/beta-catenin maturational effects were enhanced by BMP-2 and inhibited by TGF-beta. TGF-beta also inhibited activation of the Topflash reporter by beta-catenin, suggesting a direct inhibitory effect since the Topflash reporter contains only beta-catenin binding sequences. In turn beta-catenin inhibited activation of the p3TP-Luc reporter by TGF-beta, although the effect was partial. Thus, Wnt/beta-catenin signaling is a critical regulator of the rate of chondrocyte differentiation. Moreover, this pathway is modulated by members of the TGF-beta family and demonstrates the highly integrated nature of signals controlling endochondral ossification.
authors.affiliation: Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, New York 14642, USA.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Dong
authors.forename: Hicham
authors.initials: H
authors.lastname: Drissi
authors.forename: Mo
authors.initials: M
authors.lastname: Chen
authors.forename: Di
authors.initials: D
authors.lastname: Chen
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zuscik
authors.forename: Edward M
authors.initials: EM
authors.lastname: Schwarz
authors.forename: Regis J
authors.initials: RJ
authors.lastname: O'Keefe
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002454:Cell Differentiation; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D019902:Chondrocytes / Q000166:cytology* / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D047468:Immunoprecipitation; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D044162:Parathyroid Hormone-Related Protein / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051820:TCF Transcription Factors; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D051153:Wnt Proteins; D051176:beta Catenin
chemical_list: D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D003598:Cytoskeletal Proteins; D036341:Intercellular Signaling Peptides and Proteins; D044162:Parathyroid Hormone-Related Protein; D012333:RNA, Messenger; D051820:TCF Transcription Factors; D015534:Trans-Activators; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D051176:beta Catenin; D008156:Luciferases