Other structural changes, previously reported in MPS-IIIA43 and MPS-I mouse models49, could modify the outcome of the binding event between HS-growth factors and receptors50–52, including the HS-FGF2 signalling, in line with similar findings reported in cells from MPS-IIIB and MPS-I patients17,18. The gene discussed is FGF2; the disease is mucopolysaccharidosis type 1.