Stress induces dynamic, cytotoxicity-antagonizing TDP-43 nuclear bodies via paraspeckle lncRNA NEAT1-mediated liquid-liquid phase separation

Graphic Abstract Highlights (Up to four bullet points. The length of each highlight cannot exceed 85 characters, including spaces) Stress induces phase-separated TDP-43 NBs to alleviate cytotoxicity The two RRMs interact with different RNAs and act distinctly in the assembly of TDP-43 NBs LncRNA NEAT1 promotes TDP-43 LLPS and is upregulated in stressed neurons The ALS-causing D169G mutation is NB-defective and forms pTDP-43 cytoplasmic foci Summary Despite the prominent role of TDP-43 in neurodegeneration, its physiological and pathological functions are not fully understood. Here, we report an unexpected function of TDP-43 in the formation of dynamic, reversible, liquid droplet-like nuclear bodies (NBs) in response to stress. Formation of NBs alleviates TDP-43-mediated cytotoxicity in mammalian cells and fly neurons. Super-resolution microscopy reveals a “core-shell” organization of TDP-43 NBs, antagonistically maintained by the two RRMs. TDP-43 NBs are partially colocalized with nuclear paraspeckles, whose scaffolding lncRNA NEAT1 is dramatically upregulated in stressed neurons. Moreover, increase of NEAT1 promotes TDP-43 liquid-liquid phase separation (LLPS) in vitro . Finally, we uncover that the ALS-associated mutation D169G impairs the NEAT1 -mediated TDP-43 LLPS and NB assembly, causing excessive cytoplasmic translocation of TDP-43 to form stress granules that become phosphorylated TDP-43 cytoplasmic foci upon prolonged stress. Together, our findings suggest a stress-mitigating role and mechanism of TDP-43 NBs, whose dysfunction may be involved in ALS pathogenesis.