Identification of gonadotropin-inhibitory hormone in the zebra finch (Taeniopygia guttata): Peptide isolation, cDNA cloning and brain distribution

Yasuko Tobari, Norio Iijima, Kenta Tsunekawa, Tomohiro Osugi, Kazuo Okanoya, Kazuyoshi Tsutsui, Hitoshi Ozawa

    Research output: Contribution to journalArticle

    66 Citations (Scopus)

    Abstract

    Two novel RFamide peptides, kisspeptins and gonadotropin-inhibitory hormone (GnIH) are neuropeptides that appear critical in the regulation of the reproductive neuroendocrine axis. GnIH was first identified in avian brain, however, kisspeptins have not been identified in birds. To determine biochemically the presence of kisspeptins and GnIH in the zebra finch, a study was conducted to isolate these two peptides from zebra finch brain. Peptides were isolated by immunoaffinity purification and only one peptide was characterized by mass spectrometry. This peptide was confirmed to be a 12-amino acid sequence with RFamide at its C-terminus; its sequence is SIKPFSNLPLRFamide (zebra finch GnIH). By this approach, however, identification of kisspeptin from zebra finch brain was not achieved. Cloned zebra finch GnIH precursor cDNA encoded three peptides that possess characteristic LPXRFamide (X = L or Q) motifs at the C-termini. In situ hybridization and immunohistochemical analysis revealed the cellular localization of zebra finch GnIH mRNA and peptide in the paraventricular nucleus and the dorsomedial nucleus of the hypothalamus. Fluorescent immunohistochemistry with confocal microscopy indicated that GnIH-immunoreactive (ir) fibers are very close appositions with gonadotropin-releasing hormone-I (GnRH-I) cells. Furthermore GnIH-ir nerve fibers were widely distributed in the multiple brain regions including the septum, preoptic area, median eminence, optic tectum and median eminence. The prominent fibers were seen in the ventral tegmental area, midbrain central gray and dorsal motor nucleus of the vagus in the medulla. Thus, GnIH may participate in not only neuroendocrine functions but also regulation of motivation for social behavior and autonomic mechanisms.

    Original languageEnglish
    Pages (from-to)816-826
    Number of pages11
    JournalPeptides
    Volume31
    Issue number5
    DOIs
    Publication statusPublished - 2010 May

    Keywords

    • Gonadotropin-inhibitory hormone (GnIH)
    • Gonadotropin-releasing hormone (GnRH)
    • Kisspeptin
    • Neuropeptides
    • Reproduction
    • Songbird

    ASJC Scopus subject areas

    • Biochemistry
    • Endocrinology
    • Physiology
    • Cellular and Molecular Neuroscience

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