Cloning, characterization and tissue-specific expression of the gene encoding bovine keratocan, a corneal keratan sulfate proteoglycan.

Keratocan is one of three major keratan sulfate proteoglycans characteristically expressed in cornea. We reported previously the sequence of bovine Kera cDNA. In this study, the complete bovine Kera gene was cloned and sequenced, and its expression pattern was determined. The Kera gene is composed of three exons and two introns that span 8.830kb of the bovine genome. The first exon contains 287 nucleotides of 5'-UTR sequence. Both of the two large introns of 1322 and 4178bp contain (CA)n repeats. The bovine Kera gene has a TATA box that is located 28bp upstream from tsp. Primer extension and S1 nuclease protection analyses were used to determine the major tsp. RPA indicate that cornea and sclera are the two tissues with the highest expression of Ktcn mRNA. This restricted expression in eye tissues, as well as the unique modification of keratocan with long keratan sulfate chains in cornea, suggests that this molecule may be important in developing and maintaining corneal transparency.