What Is Epigenetics ? Shirish Barve Professor Department of Internal Medicine Division of Gastroenterology/Hepatology
The term ‘epigenetic’ refers to all heritable changes in gene expression and chromatin organization that are independent of the DNA sequence itself.
Epigenome provides instructions and regulates the functional aspects of all the genes
Scientists Find Clue To Mechanisms Of Gene Signaling And Regulation (Aug. 23, 2007) Epigenetics To Shape Stem Cell Future (Feb. 23, 2007) Human Embryonic Stem Cells Remain Embryonic Because Of Epigenetic Factors (Oct. 8, 2007) Epigenetic Changes Discovered In Major Psychosis (Mar. 12, 2008) Epigenetics May Be The Underlying Cause For Male Infertility (Dec. 13, 2007)
Monozygous twins share a common genotype and are genetically identical <ul><li>There is significant </li></ul><ul><li>phenotypic discordance: </li></ul><ul><li>Mental disorders </li></ul><ul><li>Cancer </li></ul>
Transcriptionally active chromatin regions tend to be hyperacetylated and hypomethylated. If a region of DNA or a gene is destined for silencing, chromatin remodeling enzymes such as histone deacetylases and ATP-dependent chromatin remodelers likely begin the gene silencing process. One or more of these activities may recruit DNA methyltransferase resulting in DNA methylation, followed finally by recruitment of the methyl-CpG binding proteins. The region of DNA will then be heritably maintained in an inactive state.
Age Dependent Epigenetic differences in Monozygotic (MZ) twins
<ul><li>In the early years of life the younger MZ twins are epigenetically indistinguishable </li></ul><ul><li>Older MZ twins exhibit remarkable differences in their epigenome as evidenced by changes in the: </li></ul><ul><li>overall content and genomic distribution of 5-methylcytosine DNA and </li></ul><ul><li>histone acetylation, affecting their gene-expression portrait. </li></ul>Influence of Age on the Epigenome in MZ Twins
Epigenetics stands at the center of modern medicine because epigenetic changes, unlike DNA sequence which is the same in every cell , can occur as a result of dietary and other environmental exposure
Environment &Epigenome Mounting evidence suggests that fetuses are surprisingly susceptible to outside influences such as environmental pollutants, pesticides, and other toxins.