title: Indian hedgehog signaling regulates transcription and expression of collagen type X via Runx2/Smads interactions.
abstract: Indian hedgehog (Ihh) is essential for chondrocyte differentiation and endochondral ossification and acts with parathyroid hormone-related peptide in a negative feedback loop to regulate early chondrocyte differentiation and entry to hypertrophic differentiation. Independent of this function, we and others recently reported independent Ihh functions to promote chondrocyte hypertrophy and matrix mineralization in vivo and in vitro. However, the molecular mechanisms for these actions and their functional significance are still unknown. We recently discovered that Ihh overexpression in chondrocytes stimulated the expression of late chondrocyte differentiation markers and induced matrix mineralization. Focusing on collagen type X (Col10α1) expression and transcription, we observed that hedgehog downstream transcription factors GLI-Krüppel family members (Gli) 1/2 increased COL10A1 promoter activity and identified a novel Gli1/2 response element in the 250-bp basic promoter. In addition, we found that Ihh induced Runx2 expression in chondrocytes without up-regulating other modulators of chondrocyte maturation such as Mef2c, Foxa2, and Foxa3. Runx2 promoted Col10α1 expression in cooperation with Ihh. Further analyses using promoter assays, immunofluorescence, and binding assays showed the interaction of Gli1/2 in a complex with Runx2/Smads induces chondrocyte differentiation. Finally, we could demonstrate that Ihh promotes in vitro matrix mineralization using similar molecular mechanisms. Our data provide an in vitro mechanism for Ihh signaling to positively regulate Col10α1 transcription. Thus, Ihh signaling could be an important player for not only early chondrocyte differentiation but maturation and calcification of chondrocytes.
authors.affiliation: From the Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts 02115 and the Departments of Oral and Maxillofacial Surgery and.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Amano
authors.affiliation: From the Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts 02115 and.
authors.forename: Michael
authors.initials: M
authors.lastname: Densmore
authors.affiliation: Molecular and Cellular Biochemistry, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan.
authors.forename: Riko
authors.initials: R
authors.lastname: Nishimura
authors.affiliation: From the Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts 02115 and beate_lanske@hsdm.harvard.edu.
authors.forename: Beate
authors.initials: B
authors.lastname: Lanske
mesh_terms: D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism*; D024121:Collagen Type X / Q000235:genetics / Q000378:metabolism*; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051898:Smad1 Protein / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2
chemical_list: C570620:Col10a1 protein, mouse; D024121:Collagen Type X; D050659:Core Binding Factor Alpha 1 Subunit; C000618551:Gli2 protein, mouse; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D015513:Oncogene Proteins; D051898:Smad1 Protein; D015534:Trans-Activators; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2; C514061:ihh protein, mouse
keywords: Calcification; Chondrocyte; Col10a1; Differentiation; Gli1/Gli2-responsive Element; Hedgehog Signaling Pathway; Maturation; Runx2; Smads; Transcription