FUNCTIONAL ANALYSIS OF THE 9E3/CEF4 GENE

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The 9E3/CEF4 gene is a member of a recently discovered group of genes, sometimes referred to as the gro family, whose products are secreted proteins that have strong homologies to inflammatory mediators and are evolutionarily conserved. A clear correlation between the expression of these genes and cell growth has been demonstrated in culture. Building on these studies, I have investigated the 9E3 gene in vivo. It is expressed in normal tissues that grow by cell division, is not expressed in tissues that do not grow by cell division, and is transiently expressed early in the cell cycle when cells leave the resting stage. 9E3 expression is enhanced upon wounding, during wound healing (especially in areas of neovascularization), and in association with tumors. Cell damage in culture and specific growth factors known to be angiogenic in vivo also stimulate the expression of this gene. My observations extend the correlation between expression of the gro genes and growth and suggest a role in autocrine or paracrine growth regulation. Moreover, the elevated expression upon wounding and the high stimulation of expression by wound factors point to additional roles in wound response and/or angiogenesis. Therefore, discovering the specific function(s) of the products of these genes may be important for the understanding of response to injury, wound healing, development of tumors, and aspects of growth regulation. To initiate functional studies of the 9E3 gene, I have developed a polyclonal antibody that recognizes the protein in situ and immunoprecipitates it from cultured cells. My working hypothesis is that this gene plays an important role in wound healing and in cell growth in vivo. To test this hypothesis, I propose to: (1) Purify and characterize the 9E3 protein biochemically; (2) assess the role of the secreted forms of the protein during injury, wound healing and development of tumors; (3) determine if the protein plays a role in cell growth; (4) determine the kinetics and pathway of protein secretion. These experiments will establish whether or not 9E3 stimulates or represses growth, has chemoattractant or angiogenic properties in vivo, and affects wound healing an/or tumor growth.