Summary The pathological hallmarks of neurodegeneration are the aberrant post-translational modification and aggregation of proteins. Genetic factors, like APOE4, increase the prevalence and severity of tau, amyloid, and α-synuclein pathologies. However, the human brain is largely inaccessible during this process, limiting mechanistic understanding. Here, we developed an iPSC-based 3D model that integrates neurons, glia, myelin, and cerebrovascular cells into a human brain-like tissue (“miBrain”). Single-nucleus RNA sequencing of miBrains confirmed the presence of diverse cell populations and revealed transcriptional responses to α-synuclein pathology. Like the human brain, pathogenic α-synuclein is increased in APOE4/4 miBrains. Combinatorial experiments revealed that endolysosomal dysfunction caused by cholesterol accumulation in APOE4/4 astrocytes impairs the degradation of soluble α-synuclein leading to a pathogenic transformation that seeds α-synuclein inclusions in neurons. Collectively, this study establishes a robust model for investigating protein inclusions in human iPSC-derived brain tissue and highlights the role of astrocytes and cholesterol in APOE4-mediated pathologies.
Louise A. Mesentier-Louro, Camille Goldman, Sebastian Gaese et al.· Cell Stem Cell· 1 citation
Proteins exist as diverse proteoforms resulting from a combination of genetic variation, alternative splicing and post-translational modifications. Current methods struggle to capture this complexity at the single-molecule level. Here we introduce Iterative Mapping of proteoforms, a method that enables massively parallel interrogation of millions to billions of single-protein molecules through iterative probing with fluorescently labeled antibodies. We applied Iterative Mapping to tau, a key protein in neurodegenerative diseases, using 12 site-specific antibodies. The tau proteoform assay demonstrates high sensitivity (detecting proteoforms at 0.1% abundance), high reproducibility (median coefficient of variation <5.5%) and broad dynamic range (>3 orders of magnitude), outperforming conventional techniques in resolving closely related proteoform groups. Analysis of relevant biological samples, including organoids, mouse brains and human Alzheimer’s disease samples, revealed 130 distinct tau proteoform groups with as many as six phosphorylation events. The nonrandom distribution of these phosphorylation events suggests ordered and site-specific modification processes rather than random, stochastic accumulation. Iterative Mapping provides insights into proteoform complexity at the single-molecule level, with implications for understanding protein regulation in neurodegenerative diseases and beyond. Iterative Mapping of proteoforms enables large-scale measurement of intact proteoforms with single-molecule resolution. The approach is demonstrated here by quantifying tau proteoform groups across control samples of known composition, model systems used in tauopathy research, and human-derived brain tissue samples.
James Joly, V. Budamagunta, Zheng-Jian Zhang et al.· Nature Methods· 1 citation
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