FMR1 and fragile X syndrome: For instance, in human hiPSCs from Fragile X (FXS) patients, the FMR1 promoter region aside the 5′UTR with expanded CGG triplets (n > 200) remains in most cases hypermethylated, suggesting that once established in FXS fibroblasts, these epigenetic marks are stably maintained after reprogramming, whereas in other cases, the methylation pattern of the disease-associated locus does not reflect the profile of the donor cells [87,88,89,90].