2026-07-09 | Intra-CNS AAV9-GBA1 delivery yields species and route of administration differences in safety and transgene expression.
Adeno-associated virus (AAV) delivery of lysosomal enzymes to the brain is currently being tested in several clinical trials. However, publicly available non-human primate (NHP) studies comprehensively reporting biodistribution, transgene expression, and safety across the central nervous system (CNS) remain limited. Here, we examined AAV9-GBA1 (encoding glucocerebrosidase [GCase]) delivery to mice and NHPs. Loss-of-function GBA1 mutations cause Gaucher's disease and are risk factors for Parkinson's disease and dementia with Lewy bodies. In mice, early postnatal intracerebroventricular administration produced appreciable transgene expression and increased GCase activity in the brain without adverse findings. Two independent adult NHP studies evaluated AAV9-GBA1 brain delivery via intracisterna magna (ICM) and intraparenchymal (IPa) administration. ICM delivery produced considerable transgene expression in the spinal cord and dorsal root ganglia (DRG) neurons along with adverse microscopic findings, but limited brain expression and activity. In contrast, IPa delivery into the thalamus and/or putamen produced substantial transgene expression and GCase activity in injected and connected brain regions, with limited effects in distal regions, including the spinal cord. While no AAV-related DRG toxicity was detected with IPa, procedure- and AAV9-GBA1-related adverse microscopic brain findings were observed and associated with clinical outcomes. Further technological advances are needed to achieve safe and therapeutic AAV transgene expression in NHP brain.
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2026-07-01 | A genome-wide screen identifies that PLCG2 restrains lysosomal GCase activity.
Mutations in the GBA1 gene, which encodes the lysosomal glucocerebrosidase enzyme GCase, cause the lysosomal storage disorder Gaucher disease and represent the most common genetic risk factor for Parkinson's disease (PD). These mutations deplete lysosomal GCase activity and cause accumulation of GCase substrate, glucosylceramide, and its pathological metabolite, glucosylsphingosine. Impaired GCase activity then drives immune and neuronal dysfunction in Gaucher disease and promotes pathogenic aggregation of α-Synuclein in PD. As such, boosting the lysosomal activity of GCase is a therapeutic strategy to ameliorate substrate accumulation and prevent associated neurotoxicity. To identify the regulators of GCase activity in lysosomes, we conducted a genome-wide screen in primary mouse macrophages using a fluorescent enzyme activity reporter. By validating the screen hits in cellular biochemical and profiling assays, we identified pathways that promote or inhibit lysosomal GCase activity. Our screen identified PLCG2 as a regulator of lysosomal GCase activity. Mechanistically, PLCG2 depletion accumulates Golgi-associated phosphatidylinositols, promoting the transport of mutant GCase into lysosomes while reducing its Golgi-associated pool. Functionally, PLCG2 depletion boosts the activity of lysosomal mutant GCase, the cellular flux of glucosylceramide, and the clearance of pathogenic GCase substrates. In summary, our screen has uncovered the regulators of GCase abundance and trafficking at a whole-genome scale and identified potential pathways for future therapeutic interventions in Gaucher and Parkinson's to boost the activity of this enzyme in lysosomes.
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2026-06-23 | Patient-specific midbrain organoids with CRISPR correction recapitulate neuronopathic Gaucher disease phenotypes and enable evaluation of novel therapies.
Neuronopathic Gaucher disease (nGD) is a lysosomal storage disorder caused by GBA1 mutations, leading to defective acid β-glucosidase (GCase) and accumulation of glycosphingolipid substrates, causing inflammation and neurodegeneration. Patients with nGD manifest severe neurological symptoms, but current animal models fail to fully recapitulate the human condition, posing a major barrier to the development of effective therapies targeting the brain. To bridge this gap, we have developed midbrain-like organoids (MLOs) from human induced pluripotent stem cells of nGD patients with GBA1L444P/P415R and GBA1L444P/RecNcil mutations to model nGD brain pathogenesis. These nGD MLOs exhibited GCase deficiency, resulting in diminished enzymatic function, accumulation of lipid substrates, widespread transcriptomic changes, and impaired dopaminergic neuron differentiation, mirroring nGD pathology. GBA1 mutation correction mediated by CRISPR/Cas9 restored GCase activity, normalized lipid substrate levels, and rescued dopaminergic neuron function, confirming the causal role of GBA1 mutations during early brain development. Using this novel platform, we further evaluated therapeutic strategies, including SapC-DOPS nanovesicles delivering GCase, AAV9-GBA1 gene therapy, and substrate reduction therapy with GZ452, a glucosylceramide synthase inhibitor currently under clinical investigation. These treatments either restored GCase activity, reduced lipid substrate accumulation, improved autophagic and lysosomal abnormalities, or ameliorated dysregulated genes involved in neural development. These patient-specific, 3D neural models offer a transformative, physiologically relevant platform for unraveling disease mechanisms and accelerating the discovery of therapies for patients with nGD.
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