In FXTAS, a pathogenic premutation trinucleotide repeat expansion (50–200 repeats) in the 5′UTR of the FMR1 gene (FMRP) does not result in transcriptional repression but rather causes a toxic gain-of-function through the formation of intranuclear inclusions containing the FMR1 mRNA and sequestered RBPs [110]. Here, FMR1 is linked to fragile X-associated tremor/ataxia syndrome.