Epigenetic landscape was originally a metaphor for biological development. Its originator, Conrad Hal Waddington, said that cell fates were established in development much like a marble rolls down to the point of lowest local elevation. Waddington suggested visualising increasing irreversibility of cell type differentiation as ridges rising between the valleys where the marbles (cells) are travelling. In recent times this Waddington's notion of the epigenetic landscape has been rigorously formalized in the context of the systems dynamics state approach to the study of cell-fate, and a systematic methodology to construct a probabilistic epigenetic landscape of cell-fate attainment associated with a Boolean networks description of genetic regulatory networks has been proposed. The formalization of the epigenetic landscape notion opens the door to the understanding of the key role played by stochastic fluctuation (cellular noise) as well as physical fields in both cell differentiation and cell proliferation.
An alternative notion of epigenetic landscape refers to the combined epigenetic modifications of a given domain of DNA sequence. Epigenetic modifications include methylation of cytosine residues of DNA and post-translational modifications of the histone proteins associated with the DNA strand. The specific combination of epigenetic modifications determines the conformation of the chromatin fibre into which the DNA and histones are packaged, and can thereby regulate the transcriptional potential of the underlying genes.
Famous quotes containing the word landscape:
“The air was so elastic and crystalline that it had the same effect on the landscape that a glass has on a picture, to give it an ideal remoteness and perfection.”
—Henry David Thoreau (1817–1862)