Drosophila Ref1/ALYREF regulates transcription and toxicity associated with ALS/FTD disease etiologies

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• RNA-binding proteins (RBPs) are implicated in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).
• The precise disease mechanisms involving RBPs in ALS/FTD remain largely unknown.
• TDP-43 and C9orf72 repeat expansions are key genetic factors in ALS/FTD.

Purpose of the Study:

• To identify RNA-binding proteins (RBPs) that genetically interact with TDP-43 in Drosophila.
• To investigate the role of the mRNA export factor Ref1 (ALYREF) in TDP-43 and C9orf72-mediated toxicity.
• To explore ALYREF as a potential therapeutic target for ALS and FTD.

Main Methods:

• Unbiased genetic screen in Drosophila to identify interacting RBPs.
• Toxicity assays involving TDP-43 and C9orf72 GGGGCC repeat expansion.
• Gene knockdown experiments to assess the effect of Ref1 depletion.
• mRNA and protein level analysis.
• Immunohistochemistry in human ALS patient samples.

Main Results:

• Downregulation of Ref1 (ALYREF) mitigated TDP-43 induced toxicity in Drosophila.
• Ref1 depletion reduced toxicity associated with the C9orf72 GGGGCC repeat expansion.
• Ref1 knockdown decreased disease-related mRNA and protein levels without affecting wild-type transgenes.
• TDP-43 or C9orf72 expansion increased endogenous Ref1 mRNA levels in fly brains.
• Human ALYREF was upregulated in ALS motor neurons, particularly in C9orf72 expansion cases.

Conclusions:

• Ref1 (ALYREF) plays a significant role in the pathogenesis of TDP-43 and C9orf72-related ALS/FTD.
• ALYREF upregulation is a feature of ALS motor neurons, especially those with C9orf72 expansions.
• Downregulating ALYREF presents a potential therapeutic strategy for ALS and FTD, potentially addressing multiple disease etiologies.