FMR1 and fragile X-associated tremor/ataxia syndrome: The pathogenic mutation of FXTAS was first described in a case report (Hagerman et al., 2001), with premutation repeat expansions (55–200 CGG repeats) in the 5'UTR of fragile X mental retardation 1 (FMR1) gene, which leads to increased levels of its mRNA and greater RNA gain-of-function toxicity (Tassone et al., 2000; Jacquemont et al., 2003; Hagerman and Hagerman, 2013).