Molecular determinants and modifiers of Matrin-3 toxicity, condensate dynamics, and droplet morphology

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Matrin-3 (MATR3) is a DNA/RNA-binding protein associated with amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and distal myopathy.
• Proteotoxicity and aberrant protein aggregation, particularly of RNA-binding proteins (RBPs), are implicated in the pathogenesis of ALS and FTD.
• Dysfunctional phase separation of RBPs contributes to the development of these neurodegenerative conditions.

Purpose of the Study:

• To develop and characterize a yeast model for studying Matrin-3 (MATR3) proteotoxicity and aggregation.
• To investigate the role of MATR3's RNA-recognition motifs (RRMs) in its toxicity and condensate formation.
• To evaluate the efficacy of engineered Hsp104 variants in mitigating MATR3 toxicity.

Main Methods:

• Development of a yeast model expressing wild-type and mutant Matrin-3 (MATR3).
• Microscopy techniques to visualize MATR3 nuclear condensates and assess their dynamics and morphology.
• Genetic manipulation, including deletion of MATR3's RNA-recognition motifs (RRMs).
• Testing of engineered Hsp104 variants for their ability to rescue MATR3 toxicity.

Main Results:

• Matrin-3 (MATR3) expression in yeast leads to proteotoxicity and the formation of dynamic, shell-like nuclear condensates.
• Disease-associated MATR3 mutations disrupt condensate dynamics and morphology.
• MATR3 toxicity is primarily mediated by its RNA-recognition motifs (RRMs); deleting RRMs causes condensate coalescence.
• Engineered Hsp104 variants successfully counteract MATR3 toxicity in the yeast model.

Conclusions:

• The developed yeast model provides a valuable platform for studying Matrin-3 (MATR3) misfolding and its associated toxicity.
• MATR3's RNA-recognition motifs (RRMs) are critical drivers of its toxicity and aberrant phase separation.
• Engineered Hsp104 variants show promise as a potential therapeutic strategy for a range of ALS/FTD-associated proteinopathies, including those involving MATR3, TDP-43, and FUS.