Repurposing small molecule to target CGG repeat RNA and POLYG aggregates in fragile x-associated TREMOR/ATAXIA syndrome (FXTAS)

Abstract

Fragile X-associated tremor/ataxia syndrome (FXTAS) arises from the expansion of CGG repeats within the 5′ untranslated region (5′-UTR) of the FMR1 (Fragile X messenger ribonucleoprotein gene 1). These expanded repeat transcripts, r(CGG)exp, can accumulate as RNA foci or undergo Repeat-Associated Non-AUG (RAN) translation, leading to the production of neurotoxic homopolymeric proteins in neurons. Identifying small molecules that selectively and tightly bind to these pathogenic repeat RNAs holds significant promise as a therapeutic strategy for treating repeat expansion-related neurodegenerative disorders. This study investigates the therapeutic potential of FDA-approved small molecules capable of binding to expanded CGG repeat sequences implicated in FXTAS pathology and mitigate its associated toxicity. Through biophysical analyses, compound P2 was identified as a selective binder of CGG repeat-containing RNA motifs. Subsequent cellular assays demonstrated that P2 effectively reduced the accumulation of toxic polyglycine (FMRPolyG) proteins. Moreover, treatment with P2 led to measurable improvements in neurological and behavioral responses in in vivo models. These findings highlight P2 as a promising candidate for the treatment of FXTAS resulting from CGG repeat expansions and support the broader application of this strategy in addressing other trinucleotide repeat-associated neurodegenerative disorders. Keywords- CGG, Repeat Expansion Disorders, FXTAS, Drug Repurposing, Small molecules.