Based on the observation of significantly elevated levels of rCGG-containing FMR1 mRNA, along with either no detectable change in FMRP or slightly reduced FMRP levels in premutation carriers, an RNA-mediated gain-of-function toxicity model has been proposed for FXTAS [13]–[17]. Here, FMR1 is linked to fragile X-associated tremor/ataxia syndrome.