FMR1 and fragile X-associated tremor/ataxia syndrome: For FXTAS, current data support two non-mutually exclusive molecular pathogenesis mechanisms: transcribed PM alleles carry expanded CGG repeats that can be found in RNA foci (47) and/or inclusions (48), and the PM CGG repeat expansion induces RAN translation within the 5′ UTR of FMR1 mRNA, producing polypeptides that may be toxic (49).