The long range goals of this proposal are to define, characterize, and ultimately control the levels of expression of the PDGF A-chain gene in normal mice and in mice bred into a background of accelerated atherosclerosis. We have recently identified a powerful cell-type specific enhancer of transcription within the first intron of the PDGF A-chain gene. We now propose experiments to define the importance of this enhancer and two other inducible elements within the 5'PDGF A-chain gene promoter in cultured cells and in a transgenic mouse model. It is proposed to identify which of the inducible elements if any mediates upregulation of the PDGF A-chain gene in mice bred into an atherogenic background. We plan to characterize the first intronic enhancer region by attempting to define DNA sequences within the enhancer that are responsible for the enhancer activity and to seek, identify, and perhaps clone and characterize a potential novel transcription factor that interacts specifically with the enhancer sequences to confer cell type specificity of expression. We also have constructed a PDGF A-chain promoter expression cassette that in preliminary experiments is strongly cell-type specific and expressed with apparent identity to the cell-type specificity of PDGF A-chain gene. We plan to use both gain of function and loss of function PDGF A-chain constructs within the PDGF A-chain promoter expression cassette to study how these may interfere with what may be roles of PDGF A in normal growth and development in mice and in mice with an atherogenic background. We will seek cooperation of the PDGF A-chain gene with three other genes potentially able to induce a more """"""""aggressive"""""""" phenotype in expressing cells. We plan also to test -/- pleiotrophin homozygous loss of function mice in an atherogenic background to determine if this PDGF inducible cytokine contributes to atherosclerosis and thus potentially is a member of a sequential genetic pathway of inducible genes. These experiments should advance knowledge of the role of the product of the PDGF A-chain gene in growth of the vessel wall, in the intact animal and in atherogenesis. Those results should suggest potential sites at which modification of its regulation may be exploited by therapeutic means.
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