In contrast, in a mouse model of MPS IIIB (Sanfilippo disease), heparin sulfate—supposedly the main substance to accumulate in MPS IIB—does not accumulate to a large extent [23]; rather, the secondary accumulation of GM3 ganglioside causes abnormal phosphorylation of tau protein and CNS symptoms [24]. The gene discussed is MAPT; the disease is mucopolysaccharidosis type 3B.