The ultimate goal of the proposed studies is to understand the regulation of gene expression of connective tissue proteins; i.e., collagens and prolyl hydroxylase. Tissue-specific distribution of collagen types suggests that synthesis of collagen is subjected to the same mechanisms which govern cell differentiation. There are dynamic changes in the synthesis of collagen types as well as in the rate of collagen synthesis during corneal morphogenesis in chick embryos. It has also been observed that changes in the rate of secretion of collagen are frequently accompanied by a temporary halt in DNA synthesis. We plan to use the regulation of collagen synthesis and metabolism of prolyl hydroxylase as models to investigate factors involved in the regulation of gene expression. However, it is essential for us to characterize the collagenous components and to recognize the chronology of their synthesis during corneal morphogenesis prior to investigating the regulation of their gynthesis. The collagenous components will be isolated from different tissue layers and characterized by polyacrylamide gel electrophoresis and peptide-map analysis to identify their types and tyeir relative abundance. We will examine the biosynthesis of collagens by corneal stromas, corneal epitheliar and corneal endothelia of chick embryos at various developmental stages with special attention to the relative synthesis of various collagen types by different tissue layers. In further studies, epithelia from different developmental stages will be cultured on substrata of lenses and/or stromas to examine whether the extracellular matrix may influence the synthesis of specific collagen types. Metabolism of prolyl hydroxylase in developing corneas and in cultured L-929 fibroblasts will be used as a model to examine the hypothesis that the synthesis of """"""""luxury"""""""" proteins, that is collagen and prolyl hydroxylase, takes place when the cells are not actively engaged in propagation.
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