Heparan sulphate proteoglycans (HSPGs) have been shown to be essential in specific signalling pathways involved in cell differentiation and tissue morphogenesis during development. The importance of HSPGs and of heparan sulphate (HS) has been highlighted by the findings that a number of human genetic disorders are associated with mutations in genes encoding for HSPG protein cores or for HS biosynthetic enzymes. In order to understand the functional role of heparan sulphate in development we have focused on an enzyme involved specifically in biosynthesis of heparan sulphate, namely the heparan 2-O-sulphotransferase (HS2ST), in C.elegans. Enzyme activity assays using whole worm extracts reveal the presence of heparan 2-O-sulphotransferase activity in C.elegans. By sequence homology to vertebrate HS2STs, we have identified the sequence C34F6.4 as a C.elegans ortholog to vertebrate HS2STs and have named the gene as
hst-2. Heterologous expression of HST-2 in CHO cells deficient in HS2ST activity completely rescues the enzyme activity and the capability of the mutant cells to bind FGF-2 on their cell surface. Inhibition
hst-2 function by RNAi reduces HST-2 activity in worm lysates as assessed using exogenous substrates. Hst-2 RNAi causes severe defects in egg laying, suggesting that HST-2 modulates signalling pathways involved in egg laying. Immunohistochemical studies show that HST-2 is mainly expressed by neuronal cells. A deletion mutant of
hst-2,
ok595, shows severe defects in egg laying. Hst-2 worms are also dumpy and uncoordinated suggesting that HS is essential for normal development in C.elegans.