Human iPSC-based neurodevelopmental models of globoid cell leukodystrophy uncover patient- and cell type-specific disease phenotypes

Abstract

Globoid Cell Leukodystrophy (GLD, or Krabbe disease) is a rare lysosomal storage disease caused by inherited deficiency of {beta}-galactocerebrosidase (GALC). The build-up of galactosylsphingosine (psychosine) and other undegraded galactosylsphingolipids in the nervous system causes severe demyelination and neurodegeneration. The molecular mechanisms of GLD are poorly elucidated in neural cells and whether murine systems recapitulate critical aspects of the human disease is still to be defined. Here, we established a collection of GLD patient-specific induced pluripotent stem cell (iPSC) lines. We differentiated iPSCs from two patients (bearing different disease-causing mutations) into neural progenitors cells (NPCs) and their neuronal/glial progeny, assessing the impact of GALC deficiency and lentiviral vector-mediated GALC rescue/overexpression by means of phenotypic, biochemical, molecular, and lipidomic analysis. We show a progressive increase of psychosine during the differentiation of GLD NPCs to neurons and glia. We report an early and persistent impairment of oligodendroglial and neuronal differentiation in GLD cultures, with peculiar differences observed in the two GLD lines. GLD cells display a global unbalance of lipid composition during the iPSC to neural differentiation and early activation of cellular senescence, depending on the disease-causing mutation. Restoration of GALC activity normalizes the primary pathological hallmarks and partially rescues the differentiation program of GLD NPCs. Our results suggest that multiple mechanisms besides psychosine toxicity concur to CNS pathology in GLD and highlight the need of a timely regulated GALC expression for proper lineage commitment and differentiation of human NPCs. These findings have important implications for establishing tailored gene therapy strategies to enhance disease correction in GLD.