Glucocerebrosidase Deficiency Dysregulates Human Astrocyte Lipid Metabolism

Area of Science:

• Neuroscience
• Genetics
• Cell Biology

Background:

• Mutations in the GBA1 gene leading to glucocerebrosidase (GCase) deficiency are a major genetic risk factor for Parkinson's disease (PD).
• The specific impact of reduced GCase activity in different neural cell types, particularly astrocytes, is not fully understood.
• Investigating astrocytic GCase function is crucial for understanding PD pathogenesis.

Purpose of the Study:

• To determine the effects of GCase deficiency in human astrocytes.
• To assess the non-cell autonomous influence of these deficient astrocytes on dopaminergic neurons.
• To model Parkinson's disease using midbrain organoids derived from human pluripotent stem cells (hPSCs).

Main Methods:

• Human pluripotent stem cells (hPSCs) were differentiated into wild-type, heterozygous mutant (N370S), and knockout astrocytes.
• GCase activity, lysosomal function, lipid accumulation, and inflammatory marker secretion (CCL2) were analyzed.
• Midbrain organoids were used to co-culture astrocytes and dopaminergic neurons.
• Transcriptomics and lipidomics were employed to characterize cellular phenotypes.

Main Results:

• GCase-deficient astrocytes showed no impairment in differentiation but exhibited enlarged lysosomes and accumulated glucosylceramide (GlcCer).
• GCase deficiency exacerbated inflammatory responses and altered lipid profiles, including increased sphingomyelin and decreased triglycerides.
• Astrocytes accumulated neuronal membrane-derived GlcCer, and impaired fatty acid uptake was observed.
• GCase deficiency in astrocytes did not negatively impact dopaminergic neuron development or survival in midbrain organoids.

Conclusions:

• GCase deficiency in human astrocytes leads to impaired lipid metabolism and heightened inflammatory reactivity, not direct neurotoxicity to dopaminergic neurons.
• Dysfunctional astrocyte lipid metabolism significantly impacts intercellular signaling between neurons and astrocytes.
• Targeting astrocytic lipid metabolism presents a promising therapeutic strategy for Parkinson's disease and related neurodegenerative disorders.