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Brian C Leonard, Bernardo Yanez, VijayKrishna Raghunathan, Nicholas L Abbott, Christopher J Murphy; Species-specific variation in mucin expression from corneal epithelium. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1500.
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The precorneal tear film and corneal epithelium dictate the interfacial properties of the ocular surface and dysregulation of these components can lead to dry eye disease (DED). Membrane-associated mucins, large glycoproteins, extend into the tear film from the microvilli on the apical surface of corneal epithelial cells. These mucins function to lubricate the cornea, maintain hydration and inhibit pathogen binding. To date, very little is known about corneal epithelial mucins in the macaque, dog and rabbit although these species are frequently used in drug development and testing. The purpose of this study was to characterize mucin expression in commonly used species to define the biochemical and interfacial properties of the corneal epithelium.
Corneal epithelial cells were procured from animals (rhesus macaque, dog, rabbit) recently euthanized for reasons unrelated to the study. Total RNA was isolated from one eye, and protein was extracted from the contralateral eye. RNA was reverse transcribed into cDNA and analyzed with quantitative RT-PCR for MUC1, MUC4, and MUC16 transcripts. In addition, total protein was separated using tris-acetate polyacrylamide gel electrophoresis and subsequently stained for glycoprotein.
Rhesus macaque and dog expression of corneal epithelial membrane-associated mucins (MUC1, MUC4, MUC16) was similar to the pattern seen in humans, with MUC16 being the most prevalent transcript. In contrast, the rabbit had a distinct pattern of gene expression: MUC4 > MUC1 > MUC16. High molecular weight glycoproteins were detected in corneal epithelial protein extracts from all three species.
The data demonstrate that there are species-specific variations in corneal epithelial mucins at the transcript level. The variable expression of corneal epithelial mucins likely reflects differences in host environment, pathogen exposure and tear film dynamics. Therefore, these species differences in corneal epithelial mucins should be taken into account when studying the ocular surface.
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