Development of cerebellar pathology in the canine model of mucopolysaccharidosis type IIIA (MPS IIIA)

The temporal relationship between the onset of clinical signs in the mucopolysaccharidosis type IIIA (MPS IIIA) Huntaway dog model and cerebellar pathology has not been described. Here we sought to characterize the accumulation of primary (heparan sulfate) and secondary (G_M3) substrates and onset of other changes in cerebellar tissues, and investigate the relationship to the onset of motor dysfunction in these animals. We observed that Purkinje cells were present in dogs aged up to and including 30.9months, however by 40.9months of age only ~12% remained, coincident with the onset of clinical signs. Primary and secondary substrate accumulation and inflammation were detected as early as 2.2months and axonal spheroids were observed from 4.3months in the deep cerebellar nuclei and later (11.6months) in cerebellar white matter tracts. Degenerating neurons and apoptotic cells were not observed at any time. Our findings suggest that cell autonomous mechanisms may contribute to Purkinje cell death in the MPS IIIA dog.