Nuclear export modulates TDP-43 phase transition and cytoplasmic aggregation

Area of Science:

• Neurobiology
• Molecular Biology
• Biochemistry

Background:

• TAR DNA-binding protein 43 (TDP-43) forms nuclear liquid-like assemblies, influencing its aggregation and neurotoxicity.
• The mechanisms controlling TDP-43's liquid-to-solid phase transition are not well understood.

Purpose of the Study:

• To identify cellular factors modulating TDP-43 phase behavior, particularly in an Amyotrophic Lateral Sclerosis (ALS)-associated mutant.
• To elucidate the role of nuclear export in regulating TDP-43 phase transitions and aggregation.

Main Methods:

• Chemical and genome-wide genetic screens were employed to identify TDP-43 phase regulators.
• An in vitro semi-permeabilized cell system was used to dynamically recapitulate TDP-43 phase transitions.
• Brain organoid models with ALS-associated mutations were utilized for validation.

Main Results:

• RNA splicing, protein translation, proteostasis, and nuclear export were identified as key TDP-43 phase regulators.
• Inhibition of nuclear export favors an RNA-dependent TDP-43 liquid-liquid phase separation (LLPS) state in vitro.
• Nuclear export deficiency was shown to limit pathogenic phospho-TDP-43 accumulation in ALS brain organoids.

Conclusions:

• Nuclear export is a critical regulator of TDP-43 phase transitions.
• A mechanistic framework links altered nuclear transport and phase dynamics to TDP-43 aggregation potential in neurodegeneration.