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Phenotypic manifestation of alpha-synuclein strains derived from Parkinson’s disease and multiple system atrophy in human dopaminergic neurons

ABSTRACT: Althougha-synuclein is implicated in the pathogenesis of Parkinson’s disease and related disorders, it remains unclear whether specific conformations or levels ofa-synuclein assemblies are toxic and how they cause progressive loss of human dopaminergic neurons. To address this issue, we used iPSC-derived dopaminergic neurons with a-synuclein triplication or controls where endogenous a-synuclein was imprinted into synthetic or disease-relevant conformations. We used a-synuclein fibrils generated de novo or amplified from homogenates of brains affected with Parkinson’s disease (n=3) or multiple system atrophy (n=5). We found that a 2.5-fold increase in a-synuclein levels in a-synuclein gene triplication neurons promoted seeded aggregation in a dose and time-dependent fashion, which was associated with a further increase in a-synuclein gene expression. Progressive neuronal loss was observed only in a-synuclein triplication neurons seeded with brain-amplified fibrils. Transcriptomic analysis and isogenic correction of a-synuclein triplication revealed that intraneuronalalpha-synuclein levels solely and sufficiently explained vulnerability to neuronal death

ORGANISM(S): Homo sapiens

PROVIDER: GSE171999 | GEO | 2021/04/13

REPOSITORIES: GEO

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Project description:Although-synuclein is implicated in the pathogenesis of Parkinson’s disease and related disorders, it remains unclear whether specific conformations or levels of-synuclein assemblies are toxic and how they cause progressive loss of human dopaminergic neurons. To address this issue, we used iPSC-derived dopaminergic neurons with -synuclein triplication or controls where endogenous -synuclein was imprinted into synthetic or disease-relevant conformations. We used -synuclein fibrils generated de novo or amplified from homogenates of brains affected with Parkinson’s disease (n=3) or multiple system atrophy (n=5). We found that a 2.5-fold increase in -synuclein levels in -synuclein gene triplication neurons promoted seeded aggregation in a dose and time-dependent fashion, which was associated with a further increase in -synuclein gene expression. Progressive neuronal loss was observed only in -synuclein triplication neurons seeded with brain-amplified fibrils. Transcriptomic analysis and isogenic correction of -synuclein triplication revealed that intraneuronal-synuclein levels solely and sufficiently explained vulnerability to neuronal death. Proximity-dependent biotinylation in living cells identified 56 differentially interacting proteins with endogenously assembled -synuclein including evasion of Parkinson’s disease-associated deglycase DJ-1 by aggregates triggered with brain amplified fibrils. Knockout of DJ-1 and related glyoxalase-1 in cell lines increased -synuclein aggregation. Similarly, methylglyoxal treatment or CRISPR/Cas9 knockout of DJ-1 in iPSC-derived dopaminergic neurons enhanced fibril-induced aggregation and cell death. Thus, toxicity of -synuclein strains depends on aggregate burden, which is determined by monomer levels and conformation which dictates differential interactomes. Our results define parameters for iPSC-based modellingof -synuclein pathology using brain amplified fibrils and demonstrate how Parkinson’s disease-associated genes influence the phenotypic manifestation of strains in human neurons.

Project description:Parkinson’s disease (PD) is a neurodegenerative disease characterized by progressive motor symptoms and alpha-synuclein (αsyn) aggregation in the nervous system. For unclear reasons, PD patients with certain GBA mutations (GBA-PD) have a more aggressive clinical progression. Two testable hypotheses that can potentially account for this phenomenon are that GBA1 mutations promote αsyn spread or drive the generation of highly pathogenic αsyn polymorphs (i.e., strains). We tested these hypotheses by treating homozygous GBA1 D409V knockin (KI) mice with human α-syn-preformed fibrils (PFFs) and treating wild-type mice (WT) with several αsyn-PFF polymorphs amplified from brain autopsy samples collected from patients with idiopathic PD and GBA-PD patients with either homozygous or heterozygous GBA1 mutations. Robust phosphorylated-αsyn (PSER129) positive pathology was observed at the injection site (i.e., the olfactory bulb granular layer) and throughout the brain six months following PFF injection. The PFF seeding efficiency and degree of spread were similar regardless of the mouse genotype or PFF polymorphs. We found that PFFs amplified from the human brain, regardless of patient genotype, were generally more effective seeders than wholly synthetic PFFs (i.e., non-amplified); however, PFF concentration differed between these two studies, and this might also account for the observed differences. To investigate whether the molecular composition of pathology differed between different seeding conditions, we permed Biotinylation by Antibody Recognition on PSER129 (BAR-PSER129). We found that for BAR-PSER129, the endogenous PSER129 pool dominated identified interactions, and thus, very few potential interactions were explicitly identified for seeded pathology. However, we found Dctn2 interaction was shared across all PFF conditions, and Nckap1 and Ap3b2 were unique to PFFs amplified from GBA-PD brains of heterozygous mutation carriers. In conclusion, both the genotype and αsyn strain had little effect on overall seeding efficacy and global PSER129-interactions.

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Phenotypic manifestation of alpha-synuclein strains derived from Parkinson’s disease and multiple system atrophy in human dopaminergic neurons

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