Since the discovery of pathogenic RFC1 AAGGG repeat expansion associated with CANVAS (4–7) and several other neurodegenerative diseases including the PD (11,12), MSA (13–15) and CIAP (16,17), few progress has been achieved towards a clearer understanding of molecular mechanism by which expanded AAGGG repeats exert detrimental function. The gene discussed is RFC1; the disease is Parkinson disease.