DNA methylation is a covalent modification to DNA, which occurs on cytosine residues and involves the addition of a methyl group to the C5 position (5-mc) and is catalyzed by DNA methyltransferases (DNMTs) (Bestor, 2000; Klose and Bird 2006). It is a stable mark that is important for diverse cellular processes such as X-chromosome inactivation, transcriptional silencing, allele-specific expression (imprinting) and is fundamentally important for normal embryonic development (Cedar & Bergman, 2012). DNA methylation patterns are stably propagated and studies employing imprinted loci show that DNA methylation patterns are re-established in the developing embryo despite their removal in primordial germ cells (Allegrucci, Thurston, Lucas, & Young, 2005; Li, 2002). Methylation of DNA is thought to mediate transcriptional repression via two ways; directly hindering binding of DNA-binding proteins (Watt & Molloy, 1988) and indirectly through binding of methyl CpG binding proteins and recruitment of HDACs, co-repressors and other heterochromatin associated proteins (Boyes & Bird, 1991; Klose & Bird, 2006; Nan et al., 1998; Ng et al., 1999). In the CNS, DNA methylation is a critical epigenetic regulator for normal brain development,
