Identification of chondroitin/dermatan sulfotransferases in the protochordate, Ciona intestinalis

Sulfated glycosaminoglycans are important components of connective tissues. The pattern of sulfation is important for their biological functions. Ascidians, the closest relatives of vertebrates, have a simple chordate body plan. In the present study, we identified an almost complete set of genes encoding proteins homologous to chondroitin/dermatan sulfotransferases in the genome of the ascidian Ciona intestinalis. We found eight genes encoding 4-O-sulfotransferases, eight genes encoding 6-O-sulfotransferases, and three genes encoding uronyl 2-O-sulfotransferases. The number of sulfotransferase genes was unexpectedly large, considering that ascidians do not have a well-developed endoskeleton. In addition, most of the genes within each sub-family seemed to have arisen by gene duplication events that occurred in the ascidian lineage after divergence from the main chordate lineage. This suggests that a unique pattern of sulfation independently developed during ascidian evolution. Some of the genes identified in the present study showed tissue-specific expression in the epidermis, notochord, muscle, and central nervous system. Region-specific expression in the epidermis was also observed. The present study provides useful information for further comparative and functional analyses of sulfotransferases and proteoglycans in chordate embryos.