The long-term objective of this project is to understand the structure- function relationship of human fibroblast growth factor 1 (FGF-1 or aFGF) and its role in tumorigenesis. The hypothesis to be tested in the current proposal is that brain-specific FGF-1 gene expression is controlled by tissue-specific trans-acting factors. The ultimate goal of this hypothesis is to identify, and subsequently to isolate, a brain-specific trans-acting transcription factor(s) through functional characterization of the brain-specific FGF-1.B promoter. FGF-1 was identified as a mitogen for a variety of mesenchymal cells including glial cells and endothelial cells. Several laboratories, including the investigator's have demonstrated the presence of FGF-1 mRNA and protein in motor and sensory neurons in the brain but not in glial cells. The investigator has shown that FGF-1 is expressed in gliomas, with a higher level in the more malignant glioblastoma multiform than in anaplastic astrocytoma. Other laboratories have demonstrated that high level expression of FGFR1 is associated with malignant progression in human astrocytomas. The investigator has previously shown that over-expression of FGF-1 in NIH/3T3 cells confers the recipient cells with a full spectrum of transformed phenotype including tumorigenicity. Thus, deregulation of FGF-1 promoter(s) may be a critical event in the progression of low grade glioma to higher grade glioma, a component of which is neovascularization. FGF-1 gene expression is controlled by at least four distinct promoters in a tissue-specific manner. The investigator proposes to elucidate the controlling mechanisms of FGF-1 gene expression, using the U1240MG and U251MG glioblastoma cell lines, by characterizing the cis - and trans- acting elements of the FGF-1 gene promoter 1.B which is brain- and glioma- specific. He has identified two positive cis-acting sequences (RR1 and RR2) in the 1.B promoter using luciferase reporter assays and gel shift assays. A brain-specific 37-kD protein, designated p37brn, was detected by the RR2 sequence using Southwestern blot analysis. He proposes to clone the cDNA coding for p37brn using interaction cloning with an RR2 sequence (-484 to -467). The same approach will be used to identify other transcriptional factors that modulate the promoter 1.B in the brain and gliomas. He also proposes to develop a novel approach on the basis of functional cloning to identify trans-acting factors for the promoter 1.B. Knockout mice with deletions of the brain-specific FGF-1 promoter 1.B will be generated through targeted gene replacement. Information obtained through this study will have important implications in understanding the proliferation of glial cells and progression of tumorigenesis.
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