ABSTRACT
Repeat-associated non-AUG (RAN) translation is a noncanonical translation initiation event that occurs at nucleotide-repeat expansion mutations that are associated with several neurodegenerative diseases, including fragile X-associated tremor ataxia syndrome (FXTAS), ALS, and frontotemporal dementia (FTD). Translation of expanded repeats produces toxic proteins that accumulate in human brains and contribute to disease pathogenesis. Consequently, RAN translation constitutes a potentially important therapeutic target for managing multiple neurodegenerative disorders. Here, we adapted a previously developed RAN translation assay to a high-throughput format to screen 3,253 bioactive compounds for inhibition of RAN translation of expanded CGG repeats associated with FXTAS. We identified five diverse small molecules that dose-dependently inhibited CGG RAN translation, while relatively sparing canonical translation. All five compounds also inhibited RAN translation of expanded GGGGCC repeats associated with ALS and FTD. Using CD and native gel analyses, we found evidence that three of these compounds, BIX01294, CP-31398, and propidium iodide, bind directly to the repeat RNAs. These findings provide proof-of-principle supporting the development of selective small-molecule RAN translation inhibitors that act across multiple disease-causing repeats.
Subject(s)
Amyotrophic Lateral Sclerosis/genetics , Ataxia/genetics , Fragile X Syndrome/genetics , Tremor/genetics , Trinucleotide Repeat Expansion/genetics , Amyotrophic Lateral Sclerosis/drug therapy , Animals , Ataxia/drug therapy , Azepines/pharmacology , Azepines/therapeutic use , Cells, Cultured , Circular Dichroism , DNA Repeat Expansion/drug effects , DNA Repeat Expansion/genetics , Drug Evaluation, Preclinical , Fragile X Syndrome/drug therapy , HEK293 Cells , Humans , Neurodegenerative Diseases/genetics , Propidium/pharmacology , Propidium/therapeutic use , Pyrimidines/pharmacology , Pyrimidines/therapeutic use , Quinazolines/pharmacology , Quinazolines/therapeutic use , Rats , Tremor/drug therapy , Trinucleotide Repeat Expansion/drug effectsABSTRACT
Egawa et al. recently showed the value of patient-specific induced pluripotent stem cells (iPSCs) for modeling amyotrophic lateral sclerosis in vitro. Their study and our work highlight the need for complementary assays to detect small, but potentially important, phenotypic differences between control iPSC lines and those carrying disease mutations.