Keratan sulfate: structure, biosynthesis, and function

The last 5 years have seen a marked increase in research on keratan sulfate (KS) and a concomitant increase in our understanding of the range of molec ules that carry this adaptable polysaccharide. More than 15 KS-linked prote ins have been identified and many of the genes encoding these have been clo ned. KS-containing molecules have been identified in numerous epithelial an d neural tissues in which KS expression responds to embryonic development, physiological variations, and to wound healing. A corneal cell culture syst em has been developed in which long-term KS biosynthesis is maintained. Pro gress has been made toward identification of the glycosyl- and sulfotransfe rases responsible for KS biosynthesis. A mouse knockout of a corneal KS-pro teoglycan has provided the first experimental support for the role of KS in corneal transparency. Evidence has also been presented supporting function al roles of KS in cellular recognition of protein ligands, axonal guidance, cell motility, and in embryo implantation. These findings have served to e xpand the concept of what keratan sulfate is and the potential roles it may play in the cellular biology of diverse tissues.