What is the difference between hypermethylation and hypomethylation?

Three different behaviors were defined: ‘hypermethylation’ (increased intensity in the tumor), ‘hypomethylation’ (decreased intensity in the tumor) and ‘no change’ (no substantial differences of intensity).

What does hypermethylation of DNA do?

DNA methylation is essential for silencing retroviral elements, regulating tissue-specific gene expression, genomic imprinting, and X chromosome inactivation. Importantly, DNA methylation in different genomic regions may exert different influences on gene activities based on the underlying genetic sequence.

What does DNA hypomethylation cause?

DNA hypomethylation induces a higher probability of translocation of parasitic sequences to other genomic regions, and chromosomal rearrangement resulting in chromosomal instability [21].

How does hypermethylation occur?

In many disease processes, such as cancer, gene promoter CpG islands acquire abnormal hypermethylation, which results in transcriptional silencing that can be inherited by daughter cells following cell division. Alterations of DNA methylation have been recognized as an important component of cancer development.

What is hypomethylation of DNA?

Definition. DNA hypomethylation refers to the loss of the methyl group in the 5-methylcytosine nucleotide. Methylation is a natural modification of DNA, and mainly affects the cytosine base (C) when it is followed by a guanosine (G) in mammals ( Methylation).

Where does hypomethylation occur?

In human, DNA methylation mainly occurs at CpG sites. Up to 80% of all CpG sites in human DNA are methylated. However, this methylation occurs primarily in areas where CpG density is low, or at repeat DNA sites, such as Alu elements. CpG islands are regions where CpG density is high and most of them are unmethylated.

Why does hypermethylation occur?

Hypomethylation, in general, arises earlier and is linked to chromosomal instability and loss of imprinting, whereas hypermethylation is associated with promoters and can arise secondary to gene (oncogene suppressor) silencing, but might be a target for epigenetic therapy.