Retrotransposons, reverse transcriptase and the genesis of new genetic information

Gene. 2009 Dec 15;448(2):180-6. doi: 10.1016/j.gene.2009.07.011. Epub 2009 Jul 21.


Spermatozoa of virtually all species can take up exogenous DNA or RNA molecules and internalize them into nuclei. A sperm endogenous reverse transcriptase activity can reverse-transcribe the internalized molecules in cDNA copies: exogenous RNA is reverse-transcribed in a one-step reaction, whereas DNA is first transcribed into RNA and subsequently reverse-transcribed. In either case, the newly synthesized cDNAs are delivered from sperm cells to oocytes at fertilization and are further propagated throughout embryogenesis and in tissues of adult animals. The reverse-transcribed sequences are underrepresented (below 1 copy/genome), mosaic distributed in tissues of adult individuals, transmitted in a non-Mendelian fashion from founders to F1 progeny, transcriptionally competent, variably expressed in different tissues and temporally transient, as they progressively disappear in aged animals. Based on these features, the reverse-transcribed sequences behave as extrachromosomal, biologically active retrogenes and induce novel phenotypic traits in animals. This RT-dependent mechanism, presumably originating from LINE-1 retroelements, generates transcriptionally competent retrogenes in sperm cells. These data strengthen the emerging view of a novel transgenerational genetics as the source of a continuous flow of novel epigenetic and phenotypic traits, independent from those associated to chromosomes. The distinctive features of this retrotransposon-based phenomenon share analogies with a recently discovered form of RNA-mediated inheritance, compatible with a Lamarckian-type adaptation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adaptation, Biological / genetics
  • Animals
  • Evolution, Molecular*
  • Genes*
  • Genetic Variation / genetics
  • Male
  • Mice
  • Models, Biological
  • RNA-Directed DNA Polymerase / physiology*
  • Retroelements / physiology*
  • Spermatozoa / metabolism
  • Spermatozoa / physiology


  • Retroelements
  • RNA-Directed DNA Polymerase