appplicant's abstract) - Matrix metalloproteases (MMPs) comprise a family of zinc-dependent proteolytic enzymes capable of degrading extracellular matrix and basement membrane components. Their gene expression is profoundly modulated by cytokines and growth factors, and the rate of transcription is controlled, at least in part, by the Jun/AP-1 pathway. Correct level of expression of these MMPs is necessary to ensure matrix remodeling and turnover in normal physiologic processes such as embryonic development, while their overexpression may initiate, or contribute to, pathological situations, such as cartilage degradation in rheumatoid arthritis or tumor progression and metastasis. This project is based on the investigator's extensive preliminary data on MMP gene expression and regulation in vitro, with regards to modulation by inflammatory mediators and growth factors. Specifically, the principal investigator plans first to develop transgenic mice bearing either human collagenase- or stromelysin-promoter/lacZ reporter gene constructs to monitor the activity of the two promoters in tissue during development from embryonic stages until senescence. The second part of this project is based on the investigator's recent demonstration that c-jun and jun-B, two oncogenes encoding transcription factors of the AP-1 family, exert opposite effects on collagenase gene expression and are responsible for its cell-type specific modulation by transforming growth factor-beta in fibroblasts and keratinocytes. Thus far, however, little is known about the details of AP-1 transactivation in vivo with regard to MMP gene expression and regulation. In this context, the principal investigator plans to develop transgenic mouse lines bearing either an antisense c-jun expression vector or a jun-B expression vector controlled by the c-jun promoter. The transgenic animals generated will provide ideal tools to study the involvement of the AP-1 transactivation pathway in vivo, through controlled induction/repression of either c-jun or jun-B expression. Finally, they intend to cross the Jun-modified transgenic mice with the MMP promoter/lacZ mice in order to generate double homozygote animals which allow controlled modulation of Jun expression and parallel detection of MMP promoter activity. These animal models will allow in vivo studies on the regulation of collagenase and stromelysin genes by growth factors and cytokines, with particular emphasis on the Jun/AP-1 signaling, enabling characterization of the molecular pathways that regulate connective tissue degradation and remodeling in vivo.
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