Characterization of the genomic corticotropin-releasing factor (CRF) gene from Xenopus laevis: two members of the CRF family exist in amphibians

Mol Endocrinol. 1992 Oct;6(10):1716-24. doi: 10.1210/mend.6.10.1448118.


In mammals, the release of pituitary ACTH is stimulated by CRF. Two related peptides exist in nonmammalian vertebrates, sauvagine from frog skin and urotensin-I from the urophysis of teleost fish. Their related structures (approximately 50%) and capacity to stimulate the release of ACTH from mammalian and fish pituitaries has led to the proposal that sauvagine and urotensin-I are homologs of mammalian CRF. However, sauvagine does not appear to stimulate ACTH release in amphibians, although mammalian CRF (ovine) induces a potent response from amphibian pituitaries. This could indicate that the main function of sauvagine does not involve ACTH regulation and suggests that an additional CRF-like peptide exists in Amphibia. We report here the isolation of two highly homologous CRF-like genes from the frog, Xenopus laevis. Analysis of the expression pattern of these CRF-like genes revealed mRNA in splenic tissue and in the preoptic nucleus and paraventricular organ of the brain. The amino acid sequence of the mature peptide regions (1-41) of both X. laevis genes is strikingly conserved, sharing more than 93% homology with mammalian CRFs, yet only 50% homology with sauvagine. In view of the fact that these new amphibian CRF-like genes share far greater homology with mammalian CRF than that exhibited by sauvagine, we propose that the new Xenopus CRF-like genes are the amphibian counterparts to mammalian CRF. Thus, two members of the CRF family have now been identified in the Amphibia, namely CRF and sauvagine.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Brain / cytology
  • Brain / physiology*
  • Cloning, Molecular
  • Corticotropin-Releasing Hormone / genetics*
  • DNA / genetics
  • DNA / isolation & purification
  • Gene Expression
  • Humans
  • In Situ Hybridization
  • Molecular Sequence Data
  • Multigene Family*
  • Organ Specificity
  • Polymerase Chain Reaction / methods
  • Sequence Homology, Amino Acid
  • Spleen / physiology
  • TATA Box
  • Xenopus laevis


  • DNA
  • Corticotropin-Releasing Hormone