CONTROL OF TYPE I COLLAGEN GENES IN WILD TYPE AND TIGHT SKIN 1 MICE

tgf -增加了成纤维细胞中I型胶原蛋白的水平

TGFbeta increases the levels of type I collagen in fibroblasts and at least part of this stimulation is mediated by transcriptional mechanisms. One of the hallmarks of fibrotic diseases including Systemic Sclerosis is an abnormal accumulation of type I collagen and other extracellular matrix (ECM) components in the skin and some internal organs, but the mechanisms of this abnormal accumulation are poorly understood. It has been postulated that excess TGFbeta might mediate the exaggerated accumulation of ECM components. A similar abnormal accumulation of type I collagen and other ECM components is found in the autosomal dominant Tight Skin mutant mice (tsk1) in which a partial in- frame duplication of the fibrillin 1 gene has been directly linked to the abnormal phenotype. Our laboratory has recently identified a potent far-upstream enhancer in the mouse pro alpha2(I) collagen gene which directs high levels of expression of reporter genes in transgenic mice specifically in fibroblasts of the skin and visceral organs. Since a spatial and temporal correlation exists between the presence of extracellular TGFbeta and the activation of type I collagen genes in these tissues during embryonic development, we postulate that the Colla2 upstream enhancer may contain elements that are responsive to TGFbeta. To further explore the mechanisms by which TGFbeta increases type I collagen synthesis and those leading to the abnormal accumulation of type I collagen in tsk1 mutant mice, we propose the following Specific Aims. (a) Delineate sequences in the Colla2 far-upstream enhancer that are responsive to TGFbeta in vivo. (b) Delineate sequences within the Colla2 far-upstream enhancer and/or proximal promoter which are responsive to signals that cause increased type I collagen synthesis in tsk1 mutant mice. (c) Generate and characterize transgenic mice in which the activity of the TGFbeta signaling pathway in fibroblasts is increased or decreased. (d) Examine the effects on the activity of the Colla2 upstream enhancer of dominant negative and constitutively active mutants of signaling components of the TGFbeta pathway in fibroblasts in culture. (f) Measure the levels of activity of the TGFbeta signaling pathway in fibroblasts of normal and tsk1 mice.