The transcription factor AP-2ɛ regulates CXCL1 during cartilage development and in osteoarthritis.

Abstract

OBJECTIVE:

Recently, the transcription factor AP-2ɛ was shown to be a regulator of hypertrophy in cartilage and to be differentially expressed in osteoarthritis (OA). However, the only known target gene of AP-2ɛ up to date is integrin alpha10. To better characterize the function of AP-2ɛ in cartilage we screened for additional target genes.

DESIGN:

Promoter analysis, ChIP-assays and electrophoretic mobility shift assay were used to characterize the regulation of a new AP-2ɛ target gene in detail.

RESULTS:

In this study, we determined the chemokine CXCL1, already known to be important in osteoarthritis (OA), as a new target gene of AP-2ɛ. We could confirm that CXCL1 is expressed in chondrocytes and significantly over-expressed in OA-chondrocytes. Transient transfection of chondrocytes with an AP-2ɛ expression construct led to a significant increase of the CXCL1 mRNA level in these cells. We identified three potential AP-2 binding sites within the CXCL1 promoter and performed luciferase assays, indicating that an AP-2 binding motif (AP-2.2) ranging from position -135 to -144 bp relative to the translation start is responsive to AP-2ɛ. This result was further addressed by site-directed mutagenesis demonstrating that activation of the CXCL1 promoter by AP-2ɛ is exclusively dependent on AP-2.2. Chromatin immunoprecipitation and electromobility shift assays confirmed the direct binding of AP-2ɛ to the CXCL1 promoter in OA-chondrocytes at this site.

CONCLUSION:

These findings revealed CXCL1 as a novel target gene of AP-2ɛ in chondrocytes and support the important role of AP-2ɛ in cartilage.

• Authors: A-K Wenke, S Niebler, S Grässel, A K Bosserhoff
• Journal: Osteoarthritis and cartilage (Osteoarthritis Cartilage) Vol. 19 Issue 2 Pg. 206-12 (Feb 2011) ISSN: 1522-9653 [Electronic] England
• PMID: 21134476 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2010 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Chemical References

• CXCL1 protein, human
• Chemokine CXCL1
• RNA, Messenger
• Transcription Factor AP-2

Topics

• Aged
• Cartilage (metabolism)
• Cells, Cultured
• Chemokine CXCL1 (metabolism)
• Chondrocytes (metabolism)
• Electrophoresis
• Female
• Gene Expression Regulation
• Humans
• Male
• Middle Aged
• Osteoarthritis (metabolism)
• RNA, Messenger (metabolism)
• Transcription Factor AP-2 (genetics, metabolism)
• Transfection