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Cloning and characterisation of gonadotropin-releasing hormone receptors from species in non-mammalian vertebrate classes : amphibia and osteichthyes
Two or more forms of gonadotropin-releasing hormone (GnRH) have been isolated from most vertebrate species. In most species, GnRH variants have been shown to occur in distinct areas of the peripheral and central nervous systems, the gonads and other peripheral organs. Although GnRH is a primary regu...
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| Language: | English |
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Division of Chemical Pathology
2018
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| _version_ | 1867613286507216896 |
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| access_status_str | Open Access |
| author | Troskie, Brigitte Elise |
| author2 | Illing, Nicola |
| author_browse | Illing, Nicola Troskie, Brigitte Elise |
| author_facet | Illing, Nicola Troskie, Brigitte Elise |
| author_sort | Troskie, Brigitte Elise |
| collection | Thesis |
| description | Two or more forms of gonadotropin-releasing hormone (GnRH) have been isolated from most vertebrate species. In most species, GnRH variants have been shown to occur in distinct areas of the peripheral and central nervous systems, the gonads and other peripheral organs. Although GnRH is a primary regulator of gonadotropin secretion, it has been shown to have additional roles such as the regulation of growth hormone secretion in goldfish and the inhibition of a potassium current (M-current) in amphibian sympathetic ganglia. This raises the possibility of the occurrence of multiple GnRH receptor subtypes. This thesis describes the cloning and characterisation of GnRH receptor subtypes from two nonmammalian vertebrates, the Amphibian, Xenopus laevis and the Osteichthyes, Carassius auratus (goldfish). Using degenerate primers designed to the mammalian GnRH receptors two putative receptor subtypes were identified from both X. laevis (X/a.1 and X/b.1) and goldfish (GfA and GfB) genomic DNA. The full-length cDNA for X/a.1, was cloned from pituitary cDNA. When transiently expressed in COS-1 cells, this clone showed a GnRH-dependent stimulation of inositol phosphates. No full-length clone for X/b.1 could be isolated using cDNA from several different tissues. A partially processed transcript was, however, amplified from sympathetic ganglia cDNA. These ganglia showed specific binding to a chicken GnRH II (cGnRH II) agonist and cGnRH II immunoreactivity was also detected in extracts from the ganglia. The expression, function and pharmacology of clone X/b.1, thus remains unknown, but the presence of cGnRH II-specific binding sites on membranes from the sympathetic ganglia with distinctly different pharmacology, implies the presence of a second GnRH receptor subtype in these neurons. Full-length cDNA clones of GfA and GfB were amplified from goldfish pituitary and brain cDNA respectively. These receptors had a 71% amino acid identity to each other and a 43% amino acid identity to the human GnRH receptor. The pharmacology of these two GnRH receptor subtypes was investigated by transient expression in COS-1 cells. The GfA and GfB receptors had different pharmacologies as demonstrated by their selectivities for GnRH analogues. In situ hybridisation revealed a distinct expression pattern of the goldfish GnRH receptor subtypes in the brain, gonads and liver (Dr R. Peter, University of Alberta). The full-length receptors cloned from the pituitaries and brain of X. /aevis and the goldfish have a low homology to the cloned mammalian GnRH receptors and have several different features, such as the presence of an intracellular carboxy-terminal tail. This thesis, describing the primary structure and characterisation of ligand selectivity of non-mammalian GnRH receptors, provides some useful foundations for future work towards understanding ligand recognition in the GnRH receptor. The description of multiple receptor subtypes in the goldfish and possibly in X. laevis also provides valuable information into alternative roles of GnRH and its receptor, which we are only beginning to understand. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/26916 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:43.673Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| publisher | Division of Chemical Pathology |
| publisherStr | Division of Chemical Pathology |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/26916 Cloning and characterisation of gonadotropin-releasing hormone receptors from species in non-mammalian vertebrate classes : amphibia and osteichthyes Troskie, Brigitte Elise Illing, Nicola Millar, Robert P Chemical Pathology Two or more forms of gonadotropin-releasing hormone (GnRH) have been isolated from most vertebrate species. In most species, GnRH variants have been shown to occur in distinct areas of the peripheral and central nervous systems, the gonads and other peripheral organs. Although GnRH is a primary regulator of gonadotropin secretion, it has been shown to have additional roles such as the regulation of growth hormone secretion in goldfish and the inhibition of a potassium current (M-current) in amphibian sympathetic ganglia. This raises the possibility of the occurrence of multiple GnRH receptor subtypes. This thesis describes the cloning and characterisation of GnRH receptor subtypes from two nonmammalian vertebrates, the Amphibian, Xenopus laevis and the Osteichthyes, Carassius auratus (goldfish). Using degenerate primers designed to the mammalian GnRH receptors two putative receptor subtypes were identified from both X. laevis (X/a.1 and X/b.1) and goldfish (GfA and GfB) genomic DNA. The full-length cDNA for X/a.1, was cloned from pituitary cDNA. When transiently expressed in COS-1 cells, this clone showed a GnRH-dependent stimulation of inositol phosphates. No full-length clone for X/b.1 could be isolated using cDNA from several different tissues. A partially processed transcript was, however, amplified from sympathetic ganglia cDNA. These ganglia showed specific binding to a chicken GnRH II (cGnRH II) agonist and cGnRH II immunoreactivity was also detected in extracts from the ganglia. The expression, function and pharmacology of clone X/b.1, thus remains unknown, but the presence of cGnRH II-specific binding sites on membranes from the sympathetic ganglia with distinctly different pharmacology, implies the presence of a second GnRH receptor subtype in these neurons. Full-length cDNA clones of GfA and GfB were amplified from goldfish pituitary and brain cDNA respectively. These receptors had a 71% amino acid identity to each other and a 43% amino acid identity to the human GnRH receptor. The pharmacology of these two GnRH receptor subtypes was investigated by transient expression in COS-1 cells. The GfA and GfB receptors had different pharmacologies as demonstrated by their selectivities for GnRH analogues. In situ hybridisation revealed a distinct expression pattern of the goldfish GnRH receptor subtypes in the brain, gonads and liver (Dr R. Peter, University of Alberta). The full-length receptors cloned from the pituitaries and brain of X. /aevis and the goldfish have a low homology to the cloned mammalian GnRH receptors and have several different features, such as the presence of an intracellular carboxy-terminal tail. This thesis, describing the primary structure and characterisation of ligand selectivity of non-mammalian GnRH receptors, provides some useful foundations for future work towards understanding ligand recognition in the GnRH receptor. The description of multiple receptor subtypes in the goldfish and possibly in X. laevis also provides valuable information into alternative roles of GnRH and its receptor, which we are only beginning to understand. 2018-01-24T11:46:18Z 2018-01-24T11:46:18Z 1998 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/26916 eng application/pdf Division of Chemical Pathology Faculty of Health Sciences University of Cape Town |
| spellingShingle | Chemical Pathology Troskie, Brigitte Elise Cloning and characterisation of gonadotropin-releasing hormone receptors from species in non-mammalian vertebrate classes : amphibia and osteichthyes |
| thesis_degree_str | Doctoral |
| title | Cloning and characterisation of gonadotropin-releasing hormone receptors from species in non-mammalian vertebrate classes : amphibia and osteichthyes |
| title_full | Cloning and characterisation of gonadotropin-releasing hormone receptors from species in non-mammalian vertebrate classes : amphibia and osteichthyes |
| title_fullStr | Cloning and characterisation of gonadotropin-releasing hormone receptors from species in non-mammalian vertebrate classes : amphibia and osteichthyes |
| title_full_unstemmed | Cloning and characterisation of gonadotropin-releasing hormone receptors from species in non-mammalian vertebrate classes : amphibia and osteichthyes |
| title_short | Cloning and characterisation of gonadotropin-releasing hormone receptors from species in non-mammalian vertebrate classes : amphibia and osteichthyes |
| title_sort | cloning and characterisation of gonadotropin releasing hormone receptors from species in non mammalian vertebrate classes amphibia and osteichthyes |
| topic | Chemical Pathology |
| url | http://hdl.handle.net/11427/26916 |
| work_keys_str_mv | AT troskiebrigitteelise cloningandcharacterisationofgonadotropinreleasinghormonereceptorsfromspeciesinnonmammalianvertebrateclassesamphibiaandosteichthyes |