Editing Epigenetics (section)

===RNA transcripts===
Sometimes, a gene, once activated, transcribes a product that directly or indirectly sustains its own activity. For example, [[Hnf4]] and [[MyoD]] enhance the transcription of many liver-specific and muscle-specific genes, respectively, including their own, through the [[transcription factor]] activity of the [[proteins]] they encode. RNA signalling includes differential recruitment of a hierarchy of generic chromatin modifying complexes and DNA methyltransferases to specific loci by RNAs during differentiation and development.<ref name="pmid19154003">{{cite journal | vauthors = Mattick JS, Amaral PP, Dinger ME, Mercer TR, Mehler MF | title = RNA regulation of epigenetic processes | journal = BioEssays | volume = 31 | issue = 1 | pages = 51–9 | date = January 2009 | pmid = 19154003 | doi = 10.1002/bies.080099 | s2cid = 19293469 | doi-access = free }}</ref> Other epigenetic changes are mediated by the production of [[alternative splicing|different splice forms]] of [[RNA]], or by formation of double-stranded RNA ([[RNAi]]). Descendants of the cell in which the gene was turned on will inherit this activity, even if the original stimulus for gene-activation is no longer present. These genes are often turned on or off by [[signal transduction]], although in some systems where [[syncytia]] or [[gap junction]]s are important, RNA may spread directly to other cells or nuclei by [[diffusion]]. A large amount of RNA and protein is contributed to the [[zygote]] by the mother during [[oogenesis]] or via [[nurse cell]]s, resulting in [[maternal effect]] phenotypes. A smaller quantity of sperm RNA is transmitted from the father, but there is recent evidence that this epigenetic information can lead to visible changes in several generations of offspring.<ref name="choi06">{{cite web| vauthors = Choi CQ |title=RNA can be hereditary molecule |website=The Scientist |url=http://www.the-scientist.com/news/display/23494/ |date=25 May 2006 |url-status=dead |archive-date=8 February 2007 |archive-url=https://web.archive.org/web/20070208182915/http://www.the-scientist.com/news/display/23494/ }}</ref>