FMR1 and fragile X-associated tremor/ataxia syndrome: The presence of the FMR1 mRNA in the intranuclear inclusions (Tassone et al., 2004) together with the observed increase of FMR1 mRNA in PM carriers (Tassone et al., 2000a) led to the suggestion that a toxic RNA gain-of-function mechanism might be responsible for the development of FXTAS.