DCHS1 and Intellectual disability: Finally, we optimized the use of dCas9-Tet1 to achieve the locus-specific manipulation of (hydroxy-)methylation in developing mouse embryos and provided one example of the potential biological relevance of our observations for one candidate 5(h)mC-dependent regulator of neurogenesis involved in neurodevelopmental malformations and mental retardation: Dchs1.