TDP-43 self-assembly is regulated by its disordered NLS-region

Cytosolic inclusions of the RNA-binding protein TDP-43 are a pathological hallmark of several neurodegenerative diseases, such as amyotrophic lateral sclerosis and frontotemporal dementia. Cellular or animal model systems often use TDP-43 mutated in its nuclear localization signal (NLS) to study its cytosolic mislocalization and aggregation. Here we show that the disordered NLS-region, in particular the basic amino acids, are crucial for self-assembly of full-length TDP-43 across size scales, ranging from small clusters to visible condensates and aggregates. Molecular dynamics simulations and NMR studies suggest that the NLS-region engages in inter-chain interactions with C-terminal aromatic residues as well as RRM1 and NTD interactions. We further demonstrate that a minimal NLS mutation (K82A) preserves TDP-43 condensation in vitro and in cells, while commonly used NLS mutations yield partially or strongly reduced self-assembly behaviors. Our data highlight TDP-43 K82A as ideal model system to study cytosolic TDP-43 aggregation in cell and animal models.