TET1 and fragile X syndrome: This notion is also supported by a recent study showing that the CRISPR/dCas9-ten-eleven translocation 1 (TET1) fusion protein-mediated fragile mental retardation 1 (FMR1) gene-targeted DNA demethylation can contract the expanded CGG repeats in fragile X syndrome (FXS) iPSCs and differentiated neurons by inducing open chromatin on the expanded CGG repeats [50].