The distribution of 5hmC is dynamically regulated during neurodevelopment, it may play a role in a number of neurodegenerative diseases [34, 35] and is also perturbed in an animal model of Rett syndrome, a neurodevelopmental disorder caused by a mutation in the MeCP2 gene which encodes a 5mC and a 5hmC binding protein which targets transcriptional activation or repression functions to its binding sites [32, 36, 37]. This evidence concerns the gene MECP2 and Rett syndrome.