It is worth noting, that Sheridan et al., [67], first reported that reprogrammed FXS fibroblasts showed an instability in the CGG trinucleotide stretch in the 5′ UTR of the FMR1 gene and some of the FXS hiPSC clones had repeat lengths shorter than the control fibroblast samples. Here, FMR1 is linked to fragile X syndrome.