The upstream 2.5 kilobases of the perlecan promoter region were studied by CAT activation in cell lines of various histological origins. This study concluded that there existed a TGF-β responsive element in the promoter just 285 base pairs upstream of the transcriptional start site. This result has been corroborated in such tissues as human colon carcinoma cells. and murine uterine epithelium by in vitro addition of the cytokine to cell culture medium. In vitro studies of TGF-β1 signaling and its effects on perlecan expression can have varying results in different cell types. In human coronary smooth muscle cells in culture, TGF-β1 signaling showed no effect on perlecan expression although it did upregulate other matrix constituents. In vivo demonstration of the dynamic regulation of perlecan and its control by extracellular signaling pathways is critical to our understanding of the protein's role in development. To this end, a transgenic mouse line was created expressing porcine TGF-β1 under the lens-specific αA-crystallin promoter and then another similar line was created but with the gene driven by the βb-crystallin promoter, corresponding to another lens-specific gene. This developmentally dynamic tissue showed a serious misregulation of extracellular matrix components including perlecan with TGF-β1 over expression. Corneal opacification occurred in both transgenic lines early in development due to greatly increased expression of perlecan, fibronectin and thrombospondin-1 in the corneal mesenchyme. The effect was more pronounced in the βB-1 Crystallin promoter-driven line.