Epigenetics is defined by hereditary changes in gene expression caused by alterations in chromatin structure, not a change in the DNA sequence. DNA methylation, an epigenetic mechanism, involves the addition of a methyl group to the DNA sequence. DNA methylation usually acts to repress genes by hindering the attachment of transcription factors or by recruiting proteins that are involved in gene repression. Environmental factors, such as nutrients, can affect the ability of DNA methylation to repress genes. Methyl donors, such as folate, methionine, choline, betaine, and vitamin B-12 add methyl groups to DNA. The effects of DNA methylation can correspond with several other diseases and disorders. For example, DNA methylation has been correlated with autism. Under the conditions of oxidative stress, a condition where the level of production of reactive oxygen species exceeds antioxidant capacity, folate and Vitamin B12 are inhibited, resulting in a decrease in all methylation reactions, including DNA methylation. Oxidative stress and decreased methylation capacity are common in autism and anomalous epigenetic regulation may associate the metabolic irregularities to disruptions in brain development. Additionally, DNA methylation also correlates with autism through DNA copy number variants (CNVs), which is a noticeable genetic risk for autism. The association of DNA methylation with CNVs raises the possibility that impaired methylation capacity might contribute to increased CNVs in autism. In the future, researchers can use this information to make better treatments.
