Novel retinoic acid receptor ligands in Xenopus embryos Academic Article Article uri icon


MeSH Major

  • Adenylyl Cyclases
  • Cyclic AMP
  • Cytoplasm
  • Organelles
  • Second Messenger Systems


  • Retinoids are a large family of natural and synthetic compounds related to vitamin A that have pleiotropic effects on body physiology, reproduction, immunity, and embryonic development. The diverse activities of retinoids are primarily mediated by two families of nuclear retinoic acid receptors, the RARs and RXRs. Retinoic acids are thought to be the only natural ligands for these receptors and are widely assumed to be the active principle of vitamin A. However, during an unbiased, bioactivity-guided fractionation of Xenopus embryos, we were unable to detect significant levels of all-trans or 9-cis retinoic acids. Instead, we found that the major bioactive retinoid in the Xenopus egg and early embryo is 4-oxoretinaldehyde, which is capable of binding to and transactivating RARs. In addition to its inherent activity, 4-oxoretinaldehyde appears to be a metabolic precursor of two other RAR ligands, 4-oxoretinoic acid and 4-oxoretinol. The remarkable increase in activity of retinaldehyde and retinol as a consequence of 4-oxo derivatization suggests that this metabolic step could serve a critical regulatory function during embryogenesis.

publication date

  • May 14, 1996



  • Academic Article


Digital Object Identifier (DOI)

  • 10.1073/pnas.93.10.4873

PubMed ID

  • 8643496

Additional Document Info

start page

  • 4873

end page

  • 8


  • 93


  • 10