Endogenous retroviruses function as species-specific enhancer elements in the placenta

Nat Genet. 2013 Mar;45(3):325-9. doi: 10.1038/ng.2553. Epub 2013 Feb 10.


The mammalian placenta is remarkably distinct between species, suggesting a history of rapid evolutionary diversification. To gain insight into the molecular drivers of placental evolution, we compared biochemically predicted enhancers in mouse and rat trophoblast stem cells (TSCs) and found that species-specific enhancers are highly enriched for endogenous retroviruses (ERVs) on a genome-wide level. One of these ERV families, RLTR13D5, contributes hundreds of mouse-specific histone H3 lysine 4 monomethylation (H3K4me1)- and histone H3 lysine 27 acetylation (H3K27ac)-defined enhancers that functionally bind Cdx2, Eomes and Elf5-core factors that define the TSC regulatory network. Furthermore, we show that RLTR13D5 is capable of driving gene expression in rat placental cells. Analysis in other tissues shows that species-specific ERV enhancer activity is generally restricted to hypomethylated tissues, suggesting that tissues permissive for ERV activity gain access to an otherwise silenced source of regulatory variation. Overall, our results implicate ERV enhancer co-option as a mechanism underlying the extensive evolutionary diversification of placental development.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acetylation
  • Animals
  • Endogenous Retroviruses / genetics*
  • Endogenous Retroviruses / metabolism
  • Enhancer Elements, Genetic / genetics*
  • Female
  • Genome
  • Histone-Lysine N-Methyltransferase / genetics
  • Histone-Lysine N-Methyltransferase / metabolism
  • Histones / metabolism
  • Humans
  • Mice
  • Placenta* / metabolism
  • Placentation
  • Pregnancy
  • Rats
  • Regulatory Sequences, Nucleic Acid
  • Species Specificity
  • Stem Cells* / cytology
  • Stem Cells* / metabolism


  • Histones
  • Histone-Lysine N-Methyltransferase

Associated data

  • GEO/GSE42207