Table 1.

Selected Examples of Known Epigenetic Alterations Associated with Diseases

Epigenetic Aberration	Enzyme Responsible	Disease	Epigenetic Alteration	Comments	Ref
DNA Methylation	DNMT1, DNMT3A, DNMT3B and DNMT3L	Rett Syndrome	Inability to “read” DNA methylation	Mutation in MeCP2	6, 7, 8
		Diabetes	Hypermethylation of PPARGC1A gene promoter		3
		Cancer	Global Hypomethylation, hypermethylation of some CpG island promoters, including CIMP		1, 2, 6
		Systemic Lupus Erythematosus	Hypomethylation of CpG islands at specific promoter regions	Decreased DNMT1 and DNMT3B expression	4
		ICF Syndrome	Hypomethylation at specific sites	DNMT3B Mutation	6, 7, 8
		ATR-X Syndrome	Hypomethylation of specific repeat and satellite sequences	ATRX Mutation	6, 7
Histone Acetylation	Histone Acetyltransferases (HATs) and HDACs	Rubinstein-Taybi Syndrome	Hypoacetylation	Mutation in CBP, a known HAT	6, 7, 8
		Diabetes	Hyperacetylation at inflammatory genes promoters		3
		Asthma	Hyperacetylation	Increased HAT activity and decreased HDAC activity	5
		Cancer	H4K16 acetylation loss	Hypomethylation of DNA repetitive sequences	1
Histone Methylation	Histone Methyltransferases (HMTs) and Histone Demethylates (HDMs)	Cancer	H4K20 tri-methylation loss	Hypomethylation of DNA repetitive sequences	1
		Sotos Syndrome	Decreased H4K20 and H3K36 tri-methylation	Loss of function of NSD1, a histone methyltransferase	98
		Huntington's Disease (HD)	Increased H3K9 tri-methylation and possibly increased H3K27 tri-methylation	Increased HMT (ESET) expression and enhanced PRC2 activity	7
miRNA Expression	N/A	Cancer	Decreased miR-101	Increased EZH2, H3K27 trimethylation	61, 74
			Decreased miR-143	Increased DNMT3A	75
			Decreased miR-29	Increased DNMT3A and 3B	76
			Increased miR-21	Decreased PTEN	83
			Increased miR-155	Lower survival rates	82