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F. Mantelli, G. Hernandez, L. Schaffer, R. Dana, S. Head, P. Argueso; Glycogene Profile of the Conjunctival Epithelium in Normal and Dry Eye Patients. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5856.
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Glycoconjugates are major components on apical cells of mucosal surfaces, such as the ocular surface epithelia. In the eye, alteration in these components or in their regulation can lead to epithelial damage and tear film instability. In this study, we aimed to analyze the expression of genes involved in glycan biosynthesis in the normal conjunctival epithelium and to investigate the genes' alteration in non-Sjogren’s dry eye.
Impression cytology samples were obtained from temporal bulbar conjunctiva of 9 normal and 9 dry eye patients. Total RNA was isolated and hybridized to the GLYCOv3 oligonucleotide microarray, which contains probes for glycosyltransferases, glycosidases, signaling molecules, nucleotide sugar transporters, proteoglycans, and glycan-binding proteins. Immunolocalization was performed to confirm expression of selected gene products.
In normal conjunctiva, 488 glycogenes (48% of the total) were expressed. In dry eye, 53 were significantly downregulated, and 1 was upregulated (p<0.05). Among the downregulated glycogenes, members of the Notch signaling pathway, Notch1, -2, -3, Jagged1, and Delta1 -involved in mucosal epithelial cell differentiation- were altered. Their presence throughout the conjunctival epithelium was confirmed by confocal microscopy, using antibodies to their extracellular domain. In addition to Notch, 16 glycogenes from the glycosyltransferase family were downregulated, including three genes (HS3ST6, EXTL2 and HS2ST1) involved in the modification of heparan sulfate, a glycosaminoglycan present on epithelial cell surfaces. The only glycogene upregulated in dry eye was interferon-induced transmembrane protein-1.
Alteration in the expression of glycogenes involved in Notch signaling pathway and in the modification of cell surface glycoconjugates may affect the wet-surface phenotype of the ocular surface and play a role in the pathogenesis of dry eye.
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