The presence of FMR1 mRNA in intranuclear inclusions (Tassone et al., 2004) in premutation patients, as observed in brain tissues from FXTAS patients (Galloway and Nelson, 2009), and increased FMR1 mRNA level in PM carriers (Tassone et al., 2000) led to the suggestion that a toxic RNA gain-of-function mechanism might be responsible for FXTAS development. Here, FMR1 is linked to fragile X-associated tremor/ataxia syndrome.