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

Cytoplasmic aggregation and nuclear depletion of TAR DNA-binding protein 43 (TDP-43) are hallmarks of several neurodegenerative disorders. Yet, recapitulating both features in cellular systems has been challenging. Here, we produced amyloid-like fibrils from recombinant TDP-43 low-complexity domain and demonstrate that sonicated fibrils trigger TDP-43 pathology in human cells, including induced pluripotent stem cell (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 its loss of function. A transcriptomic signature linked to both aggregation and nuclear loss of TDP-43, including disease-specific cryptic splicing, is identified. Cytoplasmic TDP-43 aggregates exhibit time-dependent heterogeneous morphologies as observed in patients-including compacted, filamentous, or fragmented-which involve upregulation/recruitment of protein clearance pathways. Ultimately, cell-specific progressive toxicity is provoked by seeded TDP-43 pathology in human neurons. These findings identify TDP-43-templated aggregation as a key mechanism driving both cytoplasmic gain of function and nuclear loss of function, offering a valuable approach to identify modifiers of sporadic TDP-43 proteinopathies.