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S.L. Brazeal, K.L. Moore, J.S. Rada; The Role of Tyrosine Sulfation in Extracellular Matrix Organization . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4226.
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Purpose: Tyrosine sulfation is a common post–translational modification that occurs in a variety of proteins, including the small leucine rich proteoglycans, lumican and fibromodulin. In order to better understand the biological relevance of tyrosine sulfation, the connective tissues of a knockout mouse lacking tyrosylprotein sulfotransferases TPST–1 and TPST–2, the enzymes needed to sulfate tyrosine residues, were evaluated. Methods: Eyes and forelimbs from TPST–1/TPST–2 double knockout and age matched wildtype mice were isolated on postnatal day 19 and processed for transmission electron microscopy (TEM) using standard techniques. Collagen fibril diameters in forelimb tendons and in the posterior sclera were compared in mutant and age–matched wildtype mice on electron micrographs. Results: Low power TEM indicated that the sclera and tendons of knockout mice were similar to that of wildtype tissues in terms of general connective tissue organization and collagen fibril arrangement. Examination of posterior sclera at higher (15,000 x) magnification revealed significant differences in collagen fibril diameter between knockout mice (0.094 ± 0.036 µm, mean ± sd) and wild type mice (0.079 ± 0.016 µm, mean ± sd, p<0.05, ANOVA). No significant differences were detected in collagen fibril diameters measured from forelimb tendons of knockout mice (0.104 ± 0.047 µm) as compared with wildtype mice (0.107± 0.037 µm). Conclusions: TPST–1/TPST–2 knockout mice demonstrate significant alterations in scleral collagen fibril size, possibly due to an absence of tyrosine sulfation on scleral extracellular matrix molecules required for normal collagen fibril formation and organization.
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