BioConcepts

epigeneticsEpigenetik (ger.)

• 1) The study of the development of an organism starting from the genetic material.
  category development

  1867

  Wolff war der Begründer der Epigenetik oder Entwicklungsgeschichte der Pflanzen, der Metamorphose derselben im höchsten Sinne des Worts.

  Kirchhoff, A. (1867). Die Idee der Pflanzen-Metamorphose bei Wolff und bei Göthe: 20.

  1942

  Many geneticists […] attempted to discover the processes involved in the mechanism by which the genes of the genotype bring about phenotypic effects. The first step in such an enterprise is […] to describe what can be seen of the developmental processes. For enquiries of this kind, the word ‘phenogenetics’ was coined by Haecker […]. The second and more important part of the task is to discover the causal mechanisms at work, and to relate them as far as possible to what experimental embryology has already revealed of the mechanics of development. We might use the name ‘epigenetics’ for such studies, thus emphasizing their relation to the concepts, so strongly favourable to the classical theory of epigenesis.

  Waddington, C.H. (1942). The epigenotype. Endeavour 1, 18-20: 18.

  1956

  I shall use ‘Epigenetics’ as meaning the science of developmental process in general

  Huxley, J. (1956). Epigenetics. Nature 177, 807-9: 807.

  1956

  The fact that the word ‘epigenetics’ is reminiscent of ‘epigenesis’ is to my mind one of the points in its favour. […] We all realize that, by the time development begins, the zygote contains certain ‘preformed’ characters, but that these must interact with one another, in processes of ‘epigenesis’, before the adult condition is attained. The study of the ‘preformed’ characters nowadays belongs to the discipline known as genetics; the name ‘epigenetics’ is suggested for the study of those processes which constitute the epigenesis which is also involved in development.

  Waddington, C.H. (1956). Embryology, epigenetics and biogenetics. Nature 177, 1241.

  2006

  Eipigenetics could be broadly defined as the sum of all those mechanisms necessary for the unfolding of the genetic programme for development.

  Holliday, R. (2006). Epigenetics: a historical overview. Epigenetics 1, 76-80: 76.

• 2) The study of inheritance which is not based on DNA sequence.
  category development

  1958

  [The existence of phenotypic differences between cells with the same genotype merely indicates that the expressed specificities are not determined entirely by the DNA present in the cell that other devices, epigenetic systems, regulate the expression of the genetically determined potentialities.

  Nanney, D.L. (1958). Epigenetic control systems. Proc. Natl. Acad. Sci. USA 44, 712-7: 713.]

  1994

  definition of epigenetics to include transmission of information from one generation to the next, other than the DNA sequence itself: Nuclear inheritance which is not based on changes in DNA sequence.

  Holliday, R. (1994). Epigenetics: an overview. Developmental Genetics 15, 453-7: 454.

  1996

  [This book emphasizes epigenetic control of gene expression and development, so a useful definition is: The study of mitotically and/or meiotically heritable changes in gene function that cannot be explained by changes in DNA sequence.

  Riggs, A.D., Martienssen, R.A. & Russo, V.E.A. (1996). Introduction. In: Russo, V.E.A. et al. (eds.). Epigenetic Mechanisms of Gene Regulation, 1-4: 1.]

  2006

  The current use of the term epigenetics emphasizes heritable changes in gene expression that cannot be tied to genetic variation. The original connotations of the word are retained in that the central focus is alternative gene-expression states, but emphasis is now placed on gene-expression states that are stable and transmitted through cell divisions—(meta)stable states, not simply reversible gene-expression programmes that respond nimbly to the controls exerted by trans-acting factors orchestrating development. The difference accommodates the inertia of epigenetic gene-expression states, which can be perpetuated in the absence of the conditions that established them. […] The fundamental characteristic of epigenetic phenomena is that one genotype can show alternative phenotypes, which are based on the epigenetic state of one or more loci within the genome.

  Richards, E.J. (2006). Inherited epigenetic variation – revisiting soft inheritance. Nat. Rev. Genet. 7, 395-401: 396.

  2007

  in today’s modern terms, epigenetics can be molecularly (mechanistically) defined as “The sum of the alterations to the chromatin template that collectively establish and propagate different patterns of gene expression (transcription) and silencing from the same genome.”

  Allis, C.D., Jenuwein, T. & Reinberg, D. (2007). Overview and concepts. In: Allis, C.D. et al. (eds.). Epigenetics, 23-61: 29.