L` `epigenetica` si riferisce a tutti i cambiamenti dell`espressione
L’ ‘epigenetica’ si riferisce a tutti i cambiamenti dell’espressione genica e dell’organizzazione della cromatina che sono indipendenti dalla sequenza del DNA. Epigenome provides instructions and regulates the functional aspects of all the genes Monozygous twins share a common genotype and are genetically identical There is significant phenotypic discordance: Ø Mental disorders Ø Cancer Epigenetics -DNA methylation -Histone PTMs (NC RNAs) 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 Influence of Age on the Epigenome in MZ Twins Ø In the early years of life the younger MZ twins are epigenetically indistinguishable Ø Older MZ twins exhibit remarkable differences in their epigenome as evidenced by changes in the: v overall content and genomic distribution of 5methylcytosine DNA and v histone acetylation, affecting their gene-expression portrait. L’epigenetica è al centro della medicina moderna in quanto l’epigenoma delle nostre cellule cambia nel tempo in seguito a cambiamenti ambientali e dietetici, al contraio del genoma, che è lo stesso in ogni cellula. Environment & Epigenome Mounting evidence suggests that fetuses are surprisingly susceptible to outside influences such as environmental pollutants, pesticides, and other toxins. Agouti “Twin” Sisters Coat color serves as a sensor for the degree of methylation present . Waterland R A J. Nutr. 2006;136:1706S-1710S ©2006 by American Society for Nutrition Wolff et al. showed that providing excess folic acid, vitamin B-12, choline, and betaine to female mice before and during pregnancy shifts the coat color of their Avy/a offspring toward the brown (pseudoagouti) phenotype. Waterland and Jirtle later demonstrated that this nutritionally induced change in phenotype occurs by increasing methylation at the Avy locus. Hence, the establishment of CpG methylation at Avy is sensitive to a dietary supplementation regimen designed to increase the efficiency of HCY remethylation. . Waterland R A J. Nutr. 2006;136:1706S-1710S ©2006 by American Society for Nutrition Global perturbations of histones PTMs in human cancers. H3K20me3 Lymphoma mouse SCC Fraga et al. Nat Genet. 2005. H3K16ac (MOF) Lymphoma Breast, Medulloblastoma Fraga et al. Nat Genet. 2005. H3K4me2 (MLL) Prostate Seligson et al. Nature. 2005. H3K18ac Prostate Seligson et al. Nature. 2005. H3K9me2 Prostate, Kidney Seligson et al. Am J Pathol. 2009. Ellinger et al. Prostate 2010. H3K18ac Lung, Kidney Seligson et al. Am J Pathol. 2009. Ellinger et al. Prostate 2010. H3K27me3 (Pg) Prostate Yu et al. Caner Res. 2007. Pfister ey al. Int J Cancer 2008. SUZ12 Colon Prostate Colon Breast Breast Skin Liver Lymphoma Liver Myeloma Endometrial Bladder Lung Gastric EZH2 ASH2L: important for trymetilation of H3 K4 MEN1 MEN1 MEN1 Molecular regulation of H3K4 trimethylation by ASH2L, a shared subunit of MLL complexes Melissa M Steward1, Jung-Shin Lee1, Aisling O’Donovan2,Matt Wyatt1, Bradley E Bernstein2 & Ali Shilatifard1,3 SEPTEMBER 2006 NATURE STRUCTURAL & MOLECULAR BIOLOGY With minor exceptions, all differentiation processes are triggered and maintained through epigenetic mechanisms. Epigenetic inheritance is an essential mechanism that allows the stable propagation of gene activity states from one generation of cells to the next. DNA Is Not Destiny The science of epigenetics rewrites the rules of disease, heredity and identity.