ST3GAL6

This enzyme transfers sialic acid residues to terminal galactose on glycoproteins and glycolipids, synthesizing selectin ligands essential for neutrophil recruitment during inflammation and lymphocyte homing to lymph nodes. Biallelic mutations cause autosomal recessive intellectual disability with seizures and dysmorphic features, typically manifesting in infancy or early childhood. The gene shows very low constraint against loss-of-function variants, consistent with recessive inheritance requiring biallelic mutations for disease manifestation.