N-Glycosylation and Ocular Surface Homeostasis

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Project Summary/Abstract All cells in nature are coated with a diverse mixture of glycans called the glycocalyx that functions as the primary interface with the environment. The structure of the glycocalyx is controlled by a series of glycosyltransferases, glycosidases and glycan-modifying enzymes that collectively assemble and process monosaccharide moieties to generate cell surface signatures in a tissue-specific manner. Recent findings indicate cell surface glycans perform important roles in stem cells and have a critical impact during both developmental processes and maintenance of homeostasis in the adult. This proposal centers on a major gap in our understanding of how cell surface glycans contribute to maintain limbal epithelial stem cell homeostasis. The proliferative capacity of the stem cells in tissues with high cellular turnover has to be precisely regulated to maintain regenerative capacity while preventing abnormal growth. It has become increasingly clear that modification of cell surface receptors by core fucosylation is critical to promote specific signal tranduction pathways and to regulate biological functions relevant to cell proliferation and differentiation. We hypothesize that lack of core fucosylation plays an important role in modulating the proliferative capacity of limbal epithelial stem cells and in promoting their self-renewal properties. The following specific aims will address this objective: (1) to identify glycan signatures in limbal epithelial stem cells and how they change during differentiation, (2) to investigate the contribution of FUT8, the only fucosyltransferase that catalyzes the addition of core fucose to N-glycans, in regulating growth factor receptor signaling and cellular turnover in limbal epithelial cells, and (3) to investigate whether core fucosylation can be used as a novel method to isolate and transplant limbal epithelial stem cells with high self-renewal and proliferative capacities. It is anticipated that this research will have significant translational relevance given the emerging focus on cell replacement therapies for limbal stem cell deficiency.