title: The balancing act of transcription factors C-1-1 and Runx2 in articular cartilage development.
abstract: In previous studies we found that the ets transcription factor C-1-1 is involved in articular chondrocyte development, and we and others found that the transcription factor Runx2 is required for growth plate chondrocyte maturation and ossification. We determined here whether the two factors exert reciprocal influences on their expression and function and in so doing, steer chondrocyte developmental paths. Virally driven Runx2 over-expression in cultured chick chondrocytes did indeed lead to decreased C-1-1 expression, accompanied by decreased expression of articular cartilage marker tenascin-C, decreased proliferation, and increased expression of maturation marker collagen X. In good agreement, over-expression of a dominant-negative Runx2 form had opposite phenotypic consequences. When C-1-1 itself was over-expressed in chondrocytes already undergoing maturation, maturation was halted and the cells became small, rich in tenascin-C, and mitotically quite active. To extend these observations, we misexpressed C-1-1 in mouse cartilage and found that it caused a severe inhibition of chondrocyte maturation and widespread tenascin-C expression. In sum, C-1-1 and Runx2 do influence their respective expression patterns. The factors are powerful chondrocyte regulators and their functional interrelationships may be important for steering the cells toward alternative developmental paths.
authors.affiliation: Department of Orthopaedic Surgery, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA. masahiro.iwamoto@jefferson.edu
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iwamoto
authors.forename: Eiki
authors.initials: E
authors.lastname: Koyama
authors.forename: Motomi
authors.initials: M
authors.lastname: Enomoto-Iwamoto
authors.forename: Maurizio
authors.initials: M
authors.lastname: Pacifici
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002358:Cartilage, Articular / Q000254:growth & development* / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D019902:Chondrocytes / Q000166:cytology / Q000502:physiology*; D020219:Chondrogenesis / Q000502:physiology*; D050659:Core Binding Factor Alpha 1 Subunit; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D006706:Homeostasis / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D015513:Oncogene Proteins; D019063:Tenascin / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D000071230:Transcriptional Regulator ERG
chemical_list: D015415:Biomarkers; D050659:Core Binding Factor Alpha 1 Subunit; C531115:ERG protein, mouse; D009363:Neoplasm Proteins; D015513:Oncogene Proteins; D019063:Tenascin; D014157:Transcription Factors; D000071230:Transcriptional Regulator ERG