title: Identification and localization of gonadotropin-inhibitory hormone (GnIH) orthologs in the hypothalamus of the red-eared slider turtle, Trachemys scripta elegans.
abstract: Gonadotropin-inhibitory hormone (GnIH) was discovered in 2000 as a novel hypothalamic neuropeptide that inhibited gonadotropin release in the Japanese quail. GnIH and its orthologs have a common C-terminal LPXRFamide (X=L or Q) motif, and have been identified in vertebrates from agnathans to humans, apart from reptiles. In the present study, we characterized a cDNA encoding GnIH orthologs in the brain of the red-eared slider turtle. The deduced precursor protein consisted of 205 amino-acid residues, encoding three putative peptide sequences that included the LPXRFamide motif at their C-termini. In addition, the precursor sequence was most similar to those of avian species. Immunoaffinity purification combined with mass spectrometry confirmed that three mature peptides were produced in the brain. In situ hybridization and immunohistochemistry showed that turtle GnIH-containing cells were restricted to the periventricular hypothalamic nucleus. Immunoreactive fibers were densely distributed in the median eminence. Thus, GnIH and related peptides may act on the pituitary to regulate pituitary hormone release in turtles as well as other vertebrates.
authors.affiliation: Section of Behavioral Sciences, Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521, Japan. Electronic address: ukena@hiroshima-u.ac.jp.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Ukena
authors.affiliation: Section of Behavioral Sciences, Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521, Japan.
authors.forename: Eiko
authors.initials: E
authors.lastname: Iwakoshi-Ukena
authors.affiliation: Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, Tokyo 162-8480, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Osugi
authors.affiliation: Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, Tokyo 162-8480, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Tsutsui
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D007028:Hypothalamic Hormones / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D014426:Turtles / Q000378:metabolism
chemical_list: D007028:Hypothalamic Hormones; D011498:Protein Precursors
keywords: Gonadotropin-inhibitory hormone (GnIH); Hypothalamus; Neuropeptide; Turtle; cDNA cloning