FMR1 and fragile X-associated tremor/ataxia syndrome: The premutation causes increased FMR1 mRNA levels that associates with slightly reduced FMRP expression and does not result in any neurodevelopmental syndrome, but can lead to the onset of Fragile X-associated Tremor/Ataxia Syndrome (FXTAS) after the age of 50 years (Loesch and Hagerman 2012).