title: c-Maf Transcription Factor Regulates ADAMTS-12 Expression in Human Chondrogenic Cells.
abstract: OBJECTIVE
  ADAMTS (a disintegrin and metalloproteinase with thrombospondin type-1 motif) zinc metalloproteinases are important during the synthesis and breakdown of cartilage extracellular matrix. ADAMTS-12 is up-regulated during in vitro chondrogenesis and embryonic limb development; however, the regulation of ADAMTS-12 expression in cartilage remains unknown. The transcription factor c-Maf is a member of Maf family of basic ZIP (bZIP) transcription factors. Expression of c-Maf is highest in hypertrophic chondrocytes during embryonic development and postnatal growth. We hypothesize that c-Maf and ADAMTS-12 are co-expressed during chondrocyte differentiation and that c-Maf regulates ADAMTS-12 expression during chondrogenesis.
  
  
  METHODS
  Promoter analysis and species alignments identified potential c-Maf binding sites in the ADAMTS-12 promoter. c-Maf and ADAMTS-12 co-expression was monitored during chondrogenesis of stem cell pellet cultures. Luciferase expression driven by ADAMTS-12 promoter segments was measured in the presence and absence of c-Maf, and synthetic oligonucleotides were used to confirm specific binding of c-Maf to ADAMTS-12 promoter sequences.
  
  
  RESULTS
  In vitro chondrogenesis from human mesenchymal stem cells revealed co-expression of ADAMTS-12 and c-Maf during differentiation. Truncation and point mutations of the ADAMTS-12 promoter evaluated in reporter assays localized the response to the proximal 315 bp of the ADAMTS-12 promoter, which contained a predicted c-Maf recognition element (MARE) at position -61. Electorphoretic mobility shift assay confirmed that c-Maf directly interacted with the MARE at position -61.
  
  
  CONCLUSIONS
  These data suggest that c-Maf is involved in chondrocyte differentiation and hypertrophy, at least in part, through the regulation of ADAMTS-12 expression at a newly identified MARE in its proximal promoter.
authors.affiliation: Lawrence J. Ellison Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of California Davis Medical Center, Sacramento, CA, USA.
authors.forename: Eunmee
authors.initials: E
authors.lastname: Hong
authors.affiliation: Lawrence J. Ellison Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of California Davis Medical Center, Sacramento, CA, USA.
authors.forename: Jasper
authors.initials: J
authors.lastname: Yik
authors.affiliation: Lawrence J. Ellison Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of California Davis Medical Center, Sacramento, CA, USA.
authors.forename: Derek F
authors.initials: DF
authors.lastname: Amanatullah
authors.affiliation: Lawrence J. Ellison Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of California Davis Medical Center, Sacramento, CA, USA.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Di Cesare
authors.affiliation: Lawrence J. Ellison Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of California Davis Medical Center, Sacramento, CA, USA.
authors.forename: Dominik R
authors.initials: DR
authors.lastname: Haudenschild
keywords: ADAMTS-12; c-Maf transcription factor; chondrocytes; differentiation; hypertrophy