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epigenetic

In reference to a set of reversible heritable changes in gene function or other cell phenotype that occur without a change in DNA sequence (genotype). Also see from epigenesis. These changes may: a) be induced spontaneously b) occur in response to environmental factors c) occur in response to the presence of a particular allele, even if it is absent from subsequent generations. Epigenetic information takes 3 forms: [6] 1) DNA methylation (5-methylcytosine) - generally associated with gene silencing 2) post-translational modifications of histones - acetylation, methylation, phosphorylation, ubiquitination, sumoylation - recruitment of transcription factors - activation of transcriptional enhancers - recruitment of transcriptional repressors - interaction with DNA methylation 3) higher-order chromatin structure - loop organization - partitions genome into regions of many tens of kilobases - can co-associate in topologically associated domains - allow for enhancer-promoter interactions [6] Cell differentiation is epigenetic, thus a somatic cell can be reprogrammed to become totipotent. Rearrangement of genes in the adaptive immune system represents an exception, because a portion of the DNA has been irreversibly-genetically-deleted from the genome. Epigenetics includes the study of effects that are inherited from one cell generation to the next, including 1) embryonic morphogenesis 2) regeneration 3) normal turnover of cells, tumors, cell culture 4) replication of single celled organisms Epigenetic inheritance may be maintained through meiosis, & thus may be inherited from one generation to the next in multicellular organisms. Epigenetic processes include: 1) paramutation 2) bookmarking 3) imprinting 4) gene silencing 5) X chromosome inactivation 6) position effect 7) reprogramming 8) transvection 9) maternal effects a) paternal effects are rare b) much less non-genomic material is transmitted by sperm 10) neoplastic processes a) progression of carcinogenesis b) many effects of teratogens 11) regulation of histone modifications & heterochromatin 12) technical limitations affecting parthenogenesis & cloning

Related

epigenesis epigenetic disease regulation of histone modification (GO:0031056)

Specific

epigenetic clock epigenetic transcriptional regulation

General

genetics

References

  1. Stedman's Medical Dictionary 27th ed, Williams & Wilkins, Baltimore, 1999
  2. Wikipedia, the free encyclopedia http://en.wikipedia.org
  3. Bell JT, Spector TD. A twin approach to unraveling epigenetics. Trends Genet. 2011 Mar;27(3):116-25. Review. PMID: 21257220
  4. Ollikainen M, Craig JM. Epigenetic discordance at imprinting control regions in twins. Epigenomics. 2011 Jun;3(3):295-306. Review. PMID: 22122339
  5. Wong CC, Caspi A, Williams B et al A longitudinal study of epigenetic variation in twins. Epigenetics. 2010 Aug 16;5(6):516-26 PMID: 20505345
  6. Feinberg AP The Key Role of Epigenetics in Human Disease Prevention and Mitigation. N Engl J Med 2018; 378:1323-1334. April 5, 2018 PMID: 29617578 http://www.nejm.org/doi/full/10.1056/NEJMra1402513