by David M. Sherry, Yogita Kanan, Robert Hamilton, Adam Hoffhines, Kelsey L. Arbogast, Steven J. Fliesler, Muna I. Naash, Kevin L. Moore, Muayyad R. Al-Ubaidi
To investigate the role(s) of protein-tyrosine sulfation in the retina and to determine the differential role(s) of tyrosylprotein sulfotransferases (TPST) 1 and 2 in vision, retinal function and structure were examined in mice lacking TPST-1 or TPST-2. Despite the normal histologic retinal appearance in both Tpst1-/- and Tpst2-/- mice, retinal function was compromised during early development. However, Tpst1-/- retinas became electrophysiologically normal by postnatal day 90 while Tpst2-/- mice did not functionally normalize with age. Ultrastructurally, the absence of TPST-1 or TPST-2 caused minor reductions in neuronal plexus. These results demonstrate the functional importance of protein-tyrosine sulfation for proper development of the retina and suggest that the different phenotypes resulting from elimination of either TPST-1 or -2 may reflect differential expression patterns or levels of the enzymes. Furthermore, single knock-out mice of either TPST-1 or -2 did not phenocopy mice with double-knockout of both TPSTs, suggesting that the functions of the TPSTs are at least partially redundant, which points to the functional importance of these enzymes in the retina.