A human isogenic induced pluripotent stem cell–derived dopaminergic neuron (iDA) model is presented that faithfully recapitulates the diverse biochemical, morphological, and ultrastructural features of LB neuropathology and provides critical insight into how different pathways to aSyn fibrillization and the complex interaction between aSyn fibrils and membranous organelles shape the morphological diversity of LB-like inclusions.
Abstract
The aggregation of alpha-synuclein (aSyn) into intraneuronal inclusions of heterogeneous morphology, known as Lewy bodies (LBs), is a defining hallmark of Parkinson’s disease (PD); yet, our understanding of the mechanisms underpinning their formation and heterogeneity remains incomplete. Here, we present a human isogenic induced pluripotent stem cell–derived dopaminergic neuron (iDA) model that faithfully recapitulates the diverse biochemical, morphological, and ultrastructural features of LB neuropathology. The iDA model accurately reproduces the temporal relationships between neuritic and cell-body aSyn pathology and recapitulates the proteome, posttranslational modifications, and morphological diversity of aSyn aggregates found in human PD tissue. Moreover, our work provides critical insight into how different pathways to aSyn fibrillization and the complex interaction between aSyn fibrils and membranous organelles shape the morphological diversity of LB-like inclusions. This model represents a versatile platform to investigate the mechanisms of pathology formation, maturation, and neuronal dysfunction and to develop diagnostics and therapeutics that account for the diversity of aSyn pathology in PD and related synucleinopathies.
It is shown that early complement associated pruning of inhibitory synapses precedes overt α-synuclein aggregation and neuronal loss in prodromal synucleinopathy, indicating disease-context dependent relationships between αSyn pathology and neurodegeneration.
Svenja-Lotta Rumpf, Felix L. Strübing, Karsten Nalbach et al.· Nature Communications· 0 citations
The Parkinson’s Vulnerability Index (PVI) is proposed, a hypothesis-generating multidimensional model combining genetic, enzymatic, alpha-synuclein seeding, cognitive, olfactory, and neuroimaging biomarkers to facilitate biological stratification and improve the design of mechanism-targeted clinical trials.
Livia Livinț-Popa, Andreea Nicolaie, A. Maștaleru et al.· Medical Science· 0 citations
This work generates human induced pluripotent stem cell-derived midbrain dopaminergic neurons using both a 2D differentiation protocol and a recently developed 3D method based on the microencapsulation of hiPSCs in small alginate/fibronectin beads.
A. Zanon, E. Kerschbamer, D. Riekschnitz et al.· Communications Biology· 0 citations
Multiple System Atrophy (MSA) and Parkinson's Disease (PD) are neurodegenerative diseases characterized by abundant α-synuclein (αSyn) aggregation in the brain. Compared to PD patients, MSA patients have more widespread neurodegeneration and a more aggressive disease course. PD-related αSyn pathology is primarily neuronal, whereas MSA brains characteristically display oligodendroglial inclusions. The strain hypothesis poses that polymorphisms of the αSyn aggregates, so-called strains, may explain disease heterogeneity. The present study investigates the differential properties of αSyn fibrils derived from MSA and PD patients' brains using the protein misfolding cyclic amplification (PMCA) method in cultured neurons and in vivo. MSA- and PD-derived αSyn species were administered to primary murine neuronal cell cultures or injected intrastriatally into wildtype mice, along with de novo generated αSyn fibrils of the ribbon and fibril types. The potency to induce phosphorylated αSyn (pSyn) pathology, microglial reactivity, and the extent of oligodendroglial pSyn pathology were compared among the different seeding materials using immunohistochemical and immunofluorescent approaches. In summary, the various seeding materials induced pSyn pathology of distinguishable potency and morphology. PMCA-derived material from MSA brains and the fibril polymorph induced more pSyn pathology in both neuronal cultures and in mice compared to PMCA-derived material from PD brains and the ribbon polymorph. Interestingly, amplified material from MSA brains induced significantly more oligodendroglial pSyn aggregates than amplified material from PD brains. Additionally, mice injected with the fibril polymorph, showed mild changes in microglial reactivity. Our findings suggest specific properties of the MSA- and PD-derived fibrils, and overall support the strain hypothesis.
Anne-Line Strange Laursen, K. Willén, Alexis Fenyi et al.· Neurobiology of Disease· 0 citations
Parkinson’s disease (PD) is a severe, progressive neurodegenerative disorder characterized by aggregation of the protein α-synuclein into amyloid fibrils, leading to the formation of Lewy bodies and Lewy neurites and degeneration of dopaminergic neurons in the substantia nigra. Although α-synuclein aggregation is a defining feature of PD, fundamental questions remain regarding how fibrils form, how aggregation pathways encode distinct structural polymorphs, and how these polymorphs influence prion-like propagation and neurodegeneration. This knowledge gap continues to challenge the development of effective therapeutics. This thesis addresses several of these knowledge gaps by investigating the aggregation and prion-like propagation of α-synuclein amyloid fibrils using wild-type and familial PD-associated variants. First, to understand how assembly conditions shape α-synuclein fibril formation and structure, I examined the effects of monovalent cations. I show that the physiologically abundant cations Na+ and K+, although often treated as interchangeable, produce distinct effects on aggregation kinetics and fibril morphology, demonstrating that changes in ionic conditions can reshape α-synuclein fibril assembly pathways. I next investigated consequences of fibril fragmentation, a mechanism that rarely occurs in vitro but can be significant in vivo, showing that early-onset PD variants underwent pronounced structural evolution following fragmentation, reflected in altered Thioflavin-T binding. This shows that α-synuclein fibrils are more structurally heterogenous than previously believed and that they may continue to remodel their architecture over the course of PD. To resolve such heterogeneity, I established a Thioflavin-T fluorescence-lifetime spectroscopy-based methodology for phenotyping of α-synuclein polymorphs. Cross-seeding experiments revealed variant-specific structural trajectories, including faithful templating, monomer-driven restructuring, and emergence of de novo polymorphs, highlighting the vast structural landscape accessible to α-synuclein fibrils. Finally, I investigated whether these in vitro traits influenced prion-like propagation in cells, showing that α-synuclein variants differed markedly in uptake efficiency, induction of endosomal enlargement, and ability to seed endogenous α-synuclein aggregation. These cellular outcomes aligned with the structural and kinetic behaviors observed in vitro, demonstrating that propagation efficiency is strongly shaped by intrinsic fibril properties.Altogether, this work advances the mechanistic understanding of α-synuclein aggregation and propagation in PD and highlights fibril assembly pathways and resulting fibril structure as critical targets for future therapeutic strategies.
