Glycosyltransferase required for the biosynthesis of the tetrasaccharide (GlcA-Gal-Gal-Xyl-)Ser core linker of heparan sulfate and chondroitin sulfate (PubMed:11005858). May be involved in the biosynthesis of the HNK-1 carbohydrate epitope on glycoproteins (PubMed:11005858). Required for embryonic development (PubMed:9927677). Involved in the elongation of the pharyngeal isthmus during the later stages of embryonic development (PubMed:16828468). Involved in vulval epithelium invagination (PubMed:9927677). 3-O-(beta-D-galactosyl-(1->3)-beta-D-galactosyl-(1->4)-beta-D-xylosyl)-L-seryl-[protein] + UDP-alpha-D-glucuronate = 3-O-(beta-D-GlcA-(1->3)-beta-D-Gal-(1->3)-beta-D-Gal-(1->4)-beta-D-Xyl)-L-seryl-[protein] + H(+) + UDP F1 adults accumulate eggs in the uterus. Embryos are predominantly arrested at the bean/comma embryonic stage. Belongs to the glycosyltransferase 43 family.