<i>GBA1</i> deficiency differentially affects endolysosomal trafficking in neurons versus astrocytes

Abstract Mutations in the gene glucosidase, beta acid 1 (GBA1) are the strongest genetic risk factor for Parkinson’s disease (PD) and are associated with faster disease progression. GBA1 is expressed in all cell types of the central nervous system, with some evidence supporting higher expression in glial cells than neurons. To elucidate possible specific functions in neurons versus glia, we differentiated human induced pluripotent stem cells (iPSCs) generated from an individual with PD heterozygous for the GBA1 pathogenic null variant IVS2+1 ( GBA1 IVS/+ ), homozygous GBA1 IVS2+1 isogenic to G BA1 IVS/+ ( GBA1 IVS/IVS ) and a healthy unaffected age-and sex-matched individual ( GBA1 +/+ ). GBA1 expression was reduced in GBA1 IVS/+ and GBA1 IVS/IVS neurons and astrocytes. Endolysosomal trafficking was significantly altered in G BA1- deficient neurons with enlarged early and recycling endosome and lysosome compartments in neurons but not in astrocytes. High molecular weight oligomerization of α-synuclein and phosphorylated Ser129 α-synuclein were present in GBA1 IVS/+ and GBA1 IVS/IVS neurons but not in GBA1 +/+ neurons, or in GBA1- deficient or GBA1 +/+ astrocytes. Transcriptomic analysis of GBA1 -deficient neurons and astrocytes revealed cell-type specific profiles. GBA1 deficiency in neurons downregulated immune response and upregulated cholesterol synthesis pathways, while GBA1 deficiency in astrocytes downregulated genes associated with translation and upregulated genes involved in extracellular matrix biogenesis. Transcriptomic analysis also suggests that GBA1 deficiency induces neurotoxic reactivity in astrocytes. Together, these findings indicate that GBA1 deficiency has cell type-specific effects, with increased neuronal vulnerability to endolysosomal trafficking leading to α-synucleinopathy while GBA1 deficiency in astrocytes leads to increased neurotoxic reactivity independent of endolysosomal trafficking and α-synucleinopathy. Highlights iPSC-derived neurons and astrocytes modeled GBA1 deficiency Endolysosomal trafficking defects occurred only in GBA1 -deficient neurons α-synuclein oligomers accumulated in GBA1 -deficient neurons, not astrocytes Astrocyte GBA1 loss drove neurotoxic reactive gene signatures GBA1 deficiency causes cell-type specific pathology