Mutations in Werner syndrome are almost exclusively truncating nonsense, splicing or frameshift mutations affecting WRN nuclear localization, suggesting that concomitant loss of WRN helicase and exonuclease function might be required for the onset of Werner syndrome (Fu et al., 2017; Huang et al., 2006; Matsumoto et al., 1997; Yokote et al., 2017). This evidence concerns the gene WRN and Werner syndrome.