FMR1 and fragile X-associated tremor/ataxia syndrome: Fragile X-associated tremor/ataxia syndrome (FXTAS, #300623) is a neurodegenerative disorder affecting individuals with a premutation CGG-expansion (55–200 repeats) in the 5′ untranslated region (UTR) on the Fragile X mental retardation 1 (FMR1) gene on the X-chromosome (Hagerman et al., 2001).