title: Characterization of the genomic corticotropin-releasing factor (CRF) gene from Xenopus laevis: two members of the CRF family exist in amphibians.
abstract: 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.
authors.affiliation: Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, California 92037.
authors.forename: M P
authors.initials: MP
authors.lastname: Stenzel-Poore
authors.forename: K A
authors.initials: KA
authors.lastname: Heldwein
authors.forename: P
authors.initials: P
authors.lastname: Stenzel
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: W W
authors.initials: WW
authors.lastname: Vale
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000166:cytology / Q000502:physiology*; D003001:Cloning, Molecular; D003346:Corticotropin-Releasing Hormone / Q000235:genetics*; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D015870:Gene Expression; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D005810:Multigene Family; D009928:Organ Specificity; D016133:Polymerase Chain Reaction / Q000379:methods; D017386:Sequence Homology, Amino Acid; D013154:Spleen / Q000502:physiology; D016385:TATA Box; D014982:Xenopus laevis
chemical_list: D004247:DNA; D003346:Corticotropin-Releasing Hormone