RNA-binding properties orchestrate TDP-43 homeostasis through condensate formation in vivo

Area of Science:

• Neurobiology
• Molecular Biology
• Biochemistry

Background:

• Insoluble cytoplasmic aggregates of TDP-43 are hallmarks of neurodegenerative diseases like Amyotrophic Lateral Sclerosis (ALS).
• TDP-43 protein normally resides in the nucleus, forming dynamic liquid-liquid phase separation (LLPS) condensates.
• Alterations in TDP-43 condensation properties due to mutations or post-translational modifications are implicated in disease pathogenesis.

Purpose of the Study:

• To investigate the in vivo dynamics of TDP-43 condensation in living animals.
• To understand how RNA-binding deficiencies and post-translational modifications affect TDP-43 condensation and compartmentalization.
• To elucidate the role of phase separation in regulating TDP-43 accessibility and function.

Main Methods:

• Live imaging of human TDP-43 condensation in spinal motor neurons within a living animal model.
• Single-molecule tracking to analyze the mobility of TDP-43.
• Assessment of the impact of RNA-binding deficiencies and post-translational modifications on TDP-43 behavior.

Main Results:

• Demonstrated in vivo nuclear condensation of human TDP-43 in spinal motor neurons.
• Observed aberrant condensation and altered TDP-43 compartmentalization linked to RNA-binding deficiencies and post-translational modifications.
• Single-molecule tracking revealed altered mobility profiles for RNA-binding deficient TDP-43.

Conclusions:

• Provided a critical in vivo characterization of TDP-43 condensation dynamics.
• Established phase separation as a key regulatory mechanism for TDP-43 accessibility.
• Identified molecular mechanisms underlying the regulation of functional TDP-43, offering insights into neurodegenerative disease pathology.