WRN and xeroderma pigmentosum: While mutations of DNA repair-related genes (i.e. WRN (Shimamoto et al., 2014; Cheung et al., 2014) and Fanconi genes (Raya et al., 2009; Muller et al., 2012; Yung et al., 2013)) have been revealed as a barrier to somatic cell reprogramming, we did not observe obvious impairment in reprogramming kinetics from XP patient fibroblasts.