Complementary expression of HSPG 6-O-endosulfatases and 6-O-sulfotransferase in the hindbrain of Xenopus laevis

Heparan sulfate proteoglycans (HSPGs) are abundant cell surface molecules, consisting of glycosaminoglycan (GAG) chains bound to a protein core. There is high diversity in the sulfation pattern within each GAG chain, creating specific binding sites for many proteins including cell signalling factors, whose activities and distribution are modified by their association with HSPGs (Danesin et al., 2006 and Freeman et al., 2008). Here, we describe the distinct expression of three enzymes which modify the 6-O-sulfation state of HSPGs: two 6-O-endosulfatases (Sulf1 and Sulf2), and a 6-O-sulfotransferase (6OST-1). We use in situ hybridisation to determine the spatial distribution of transcripts during tailbud stages of Xenopus laevis development, with a particular focus on neural regions where the 6-O-sulfatases are expressed ventrally and the 6-O-sulfotransferase is restricted dorsally. The complementary expression of these enzymes in the hindbrain and neural tube suggest a role for specific HSPG structure in dorsoventral patterning, possibly through modifying the activity or distribution of signalling molecules such as BMP, Sonic hedgehog, Wnt and/or FGF.