Glypican1/2/4/6 and sulfated glycosaminoglycans regulate the patterning of the primary body axis in the cnidarian Nematostella vectensis

Glypicans are members of the heparan sulfate (HS) subfamily of proteoglycans that can function in cell adhesion, cell crosstalk and as modulators of the major developmental signalling pathways in bilaterians. The evolutionary origin of these multiple functions is not well understood. In this study we investigate the role of glypicans in the embryonic and larval development of the sea anemone Nematostella vectensis, a member of the non-bilaterian clade Cnidaria. Nematostella has two glypican (gpc) genes that are expressed in mutually exclusive ectodermal domains, NvGpc1/2/4/6 in a broad aboral domain, and NvGpc3/5 in narrow oral territory. The endosulfatase NvSulf (an extracellular modifier of HS chains) is expressed in a broad oral domain, partially overlapping with both glypicans. Morpholino-mediated knockdown of NvGpc1/2/4/6 leads to an expansion of the expression domains of aboral marker genes and a reduction of oral markers at gastrula stage, strikingly similar to knockdown of the Wnt receptor NvFrizzled5/8. We further show that treatment with sodium chlorate, an inhibitor of glycosaminoglycan (GAG) sulfation, phenocopies knockdown of NvGpc1/2/4/6 at gastrula stage. At planula stage, knockdown of NvGpc1/2/4/6 and sodium chlorate treatment result in alterations in aboral marker gene expression that suggest additional roles in the fine-tuning of patterning within the aboral domain. These results reveal a role for NvGpc1/2/4/6 and sulfated GAGs in the patterning of the primary body axis in Nematostella and suggest an ancient function in regulating Frizzled-mediated Wnt signalling.