Condensate protein aggregation in ALS/FTD is regulated by GGGGCC-repeat RNA scaffolds.

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Biomolecular condensates are crucial for cellular functions but implicated in diseases.
• Mechanisms of pathogenic condensate formation and therapeutic targeting remain unclear.
• In c9ALS/FTD, C9orf72 GGGGCC repeat expansions lead to pathogenic RNA and proteins.

Purpose of the Study:

• To investigate the formation and role of GGGGCC-repeat RNA and poly(GR) cocondensates in c9ALS/FTD.
• To explore the structural basis of GGGGCC-repeat RNA in modulating poly(GR) aggregation.
• To assess the therapeutic potential of targeting RNA structures in c9ALS/FTD.

Main Methods:

• In vitro and in cellulo cocondensation assays.
• Structural analysis of GGGGCC-repeat RNA (G-quadruplex and hairpin).
• Small molecule screening targeting RNA structures.
• Assessment of cellular toxicity and nucleolar stress.

Main Results:

• GGGGCC-repeat RNA and poly(GR) form cocondensates.
• RNA G-quadruplex and hairpin structures scaffold poly(GR) aggregation, promoting solid-like condensates.
• Cocondensation exacerbates nucleolar stress and cellular toxicity.
• Small molecules targeting RNA structures reduce poly(GR) aggregation and cellular dysfunction.

Conclusions:

• RNA structure is critical in driving pathogenic protein aggregation in c9ALS/FTD.
• Targeting RNA scaffolds within pathogenic condensates offers a novel therapeutic approach.
• This study expands understanding of c9ALS/FTD pathogenesis and suggests new druggable targets.