Zebrafish models of Mucopolysaccharidosis IIIA, IIIB, and IIIC show hyperactivity, neuroinflammation and changes in oligodendrocyte cell state

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Abstract
Sanfilippo syndrome childhood dementia, also known as mucopolysaccharidosis type III (MPS III), is a rare inherited lysosomal storage disorder. Subtypes of MPS III are caused by deficiencies in one of four enzymes required for degradation of the glycosaminoglycan heparan sulfate (HS). An inability to degrade HS leads to progressive neurodegeneration and death in the second or third decades of life. Knowledge of MPS III pathogenesis is incomplete, and no effective therapies exist. We generated the hypomorphic mutations sgshS387Lfs, nagluA603Efs and hgsnatG577Sfsin the endogenous zebrafish genes orthologous to human SGSH, NAGLU, and HGSNAT that are loci for mutations causing MPS III subtypes MPS IIIA, B and C respectively. Our models display the primary MPS III disease signature of significant brain accumulation of HS, while behavioural analyses support hyperactivity phenotypes. Brain transcriptome analysis revealed changes related to lysosomal, glycosaminoglycan, immune system and iron homeostasis biology in all three models but also distinct differences in brain transcriptome state between models. The transcriptome analysis also indicated marked disturbance of the oligodendrocyte cell state in the brains of MPS IIIA, B and C zebrafish, supporting that effects on this cell type are an early and consistent characteristic of MPS III. Overall, our zebrafish models recapture key characteristics of the human disease and phenotypes seen in mouse models. Our models will allow exploitation of the zebrafish’s extreme fecundity and accessible anatomy to dissect the pathological mechanisms both common and divergent between the MPS IIIA, B, and C subtypes.

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