I. Introduction
DNA methylation (DNAm) is the addiction of a methyl group to a DNA molecule. The DNA sequence is composed by four bases: adenine (A), thymine (T), cytosine (C) and guanine (G). The most common form of DNA methylation is the methylation of cytosine which form the 5-methylcytosine (5mC) and it affects a high number of cytosines present in the genome [1]. Methylation changes the activity of DNA without changing its base sequence.