HS3ST3B1

This gene encodes a heparan sulfate 3-O-sulfotransferase that catalyzes the transfer of sulfate groups to specific glucosamine residues in heparan sulfate chains, modifying these glycosaminoglycans to create binding sites for various proteins including viral entry receptors. Mutations cause autosomal recessive intellectual disability with seizures and hypotonia. The gene shows moderate constraint to loss-of-function variants, and the resulting neurodevelopmental disorder typically manifests in early childhood.