TDP-43 seeding induces cytoplasmic aggregation heterogeneity and nuclear loss-of-function of TDP-43

Cytoplasmic aggregation and nuclear depletion of TDP-43 are hallmarks of several age-related neurodegenerative disorders. Yet, recapitulating both features in cellular systems has been a major challenge. Here, we produced amyloid-like fibrils from the recombinant low-complexity-domain of TDP-43, and demonstrate that sonicated fibrils trigger TDP-43 pathology in human cell lines and iPSC-derived neurons. Fibril-induced cytoplasmic TDP-43 inclusions acquire distinct biophysical properties, recapitulate pathological hallmarks such as phosphorylation, ubiquitin- and p62-accumulation, and recruit nuclear endogenous TDP-43 leading to nuclear-loss-of-function-driven disease-specific cryptic splicing defects. Cytoplasmic TDP-43 aggregates exhibit, with time, distinct heterogeneous morphologies as in patients including compacted, filamentous or fragmented, through the activation of cellular protein clearance pathways. Cell-specific progressive toxicity is provoked by seeded TDP-43 pathology in human neurons. These findings identify templated aggregation of TDP-43 as a key mechanism driving both cytoplasmic gain- and nuclear-loss-of-function, offering a valuable approach to identify modifiers of sporadic TDP-43 proteinopathies.