GBA1 L444P MUTATION INCREASES VULNERABILITY TO Α-SYNUCLEIN PATHOLOGY IN PRIMARY NEURONS

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by the death of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and by the accumulation of α-synuclein (α-Syn) aggregates in neuronal cell bodies, known as Lewy bodies. Clinically, PD is marked by bradykinesia, rigidity, resting tremor, and postural instability. The degeneration of dopaminergic neurons results in severe striatal dopaminergic denervation and causes a cascade of functional alterations throughout the basal ganglia circuitry. Growing evidence highlights mutations in the GBA1 gene, which encodes the lysosomal enzyme glucocerebrosidase (GCase), as the strongest risk factor to develop PD. In this project, to evaluate the susceptibility to α-Syn species, primary neurons from GBA1 mice expressing wild-type or heterozygous L444P GCase were exposed for 3h to 0.3 μM α-Syn oligomers or fibrils. Heterozygous neurons showed significantly increased internalization of α-syn oligomers compared to untreated controls. Neuronal network activity was assessed through multielectrode array (MEA) recordings. Our results show that heterozygous cultures exhibit an overall enhancement of network bursting and higher mean firing rates compared to wild-type, highlighting genotype- dependent differences in the development of excitability and functional connectivity. Notably, α-Syn exposure caused a marked reduction in neuronal activity. Single-cell patch-clamp recordings revealed that Het neurons exhibit reduced membrane capacitance and increased resistance, but decreased intrinsic excitability, as indicated by an increased rheobase. Altogether, these results underscore the impact of GCase dysfunction on neuronal network activity supporting its role as a key therapeutic target in GBA1-associated Parkinson’s disease.