Patient iPSC-derived neural stem cells display progressive enlargement of lysosomes and disruptions of glycosaminoglycan pathway and autophagy in concordance with clinical severity of Mucopolysaccharidosis I

Mucopolysaccharidosis type I (MPS I) is caused by genetic defects in alpha-L-iduronidase (IDUA), a lysosomal enzyme involved in the breakdown and recycling of glycosaminoglycans (GAGs). Although an enzyme replacement therapy is available, the efficacy for the treatment of neuropathic symptoms is limited. To facilitate drug discovery and model disease pathophysiology, we have generated neural stem cells (NSCs) from MPS I patient-derived iPSCs. NSCs exhibited characteristic disease phenotypes with deficiency of alpha-L-iduronidase (IDUA), accumulation of glycosaminoglycans (GAGs) and enlargement of lysosomes, correlating with the severity of clinical symptoms. Transcriptome profiling of NSCs revealed differential expression of 429 genes that changed more extensively in the more severe Hurler syndrome subgroup compared to the Hurler-Scheie (median severe) and Scheie (less severe) subgroups. Clustering and pathway analyses demonstrated high concordance of the severity of neurological defects with marked dysregulation of GAG biosynthesis and degradation, lysosomal function and extracellular matrix. Gene Ontology (GO) analysis identified a dramatic upregulation of autophagy pathway, especially in the Hurler syndrome. Thus, GAG accumulation in the patient cells disrupts lysosomal homeostasis affecting multiple related cellular pathways which compensates for IDUA deficiency. These dysregulated process likely lead to enhanced autophagy and more severe disease states. Our studies provide useful tools for clinical biomarker development and potential targets for drug development. Overall design: Patient iPSC-derived and control neural stem cells from Scheie, Hurler-Scheie, and Hurler disease were expression profiled in triplicate using RNA-seq.