through replication in the absence of DNA methyltransferase, resulting in the loss of the cytosine methylation in the daughter cell,93,94 a mechanism that is not applicable to postmitotic cells such as neurons. However, recent findings together with the data reviewed here support an alternative model: one that suggests that the DNA methylation pattern is dynamic and is an equilibrium of methylation and demethylation reaction.99,100We propose that DNA methylation is a reversible, like any other biological signal, and could potentially change in response to environmental and physiological signals.99-101 The notion that DNA methylation is reversible in postmitotic cells has immense implications on our understanding the potential role of DNA methylation in marking gene expression in the brain.
