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- Benedet Perea, Susana, 1972, et al.
(författare)
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Cloning of two Atlantic salmon growth hormone receptor isoforms and in vitro ligand-binding response.
- 2006
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Ingår i: Fish Physiology and Biochemistry. - : Springer Science and Business Media LLC. - 0920-1742 .- 1573-5168. ; 31:4, s. 315-329
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Tidskriftsartikel (refereegranskat)abstract
- Two isoforms of the full-length cDNA of the growth hormone receptor (GHR) of the Atlantic salmon (Salmo salar; ss) were cloned by a PCR approach using RACE. Respectively, the cDNA sequences of ssGHR isoforms 1 and 2 are 2654 and 2608 nucleotides long, with 1782 and 1773 nucleotide ORFs. The resulting coded proteins are 594 and 590 aa long, with 19 and 20 aa signal peptides. The two isoforms share 86% protein and 87% cDNA sequence similarity. Isoform 1 is most similar to other salmonid GHR isoforms 1 while isoform 2 is most similar to salmonid GHR isoforms 2 (93–95%). Similarity with other teleost species was lower (37–44%). The bioactivity of the cloned ssGHR was tested by transfecting the ssGHR isoform 1 cDNA into CHO-K1 hamster cells, incubating with recombinant salmon GH (sGH) or native ovine prolactin (oPRL), and measuring cell proliferation by the MTT assay. The ssGHR-transfected cells significantly increased proliferation when stimulated by sGH at all concentrations. oPRL stimulated ssGHR-transfected cells at higher concentrations due to receptor cross reaction. ssGHR isoforms 1 and 2 contain a single transmembrane domain and the typical conserved motifs found in other teleost GHRs, including four paired cysteine residues and five potential N-glycosylation sites in the extracellular domain, Box I and Box II, as well as seven potential tyrosine phosphorylation sites in the intracellular domain. However, in salmonids, these motifs differ from those of other teleosts, and could be responsible for differentiated hormone binding, signal transduction and response.
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| 2. |
- Benedet Perea, Susana, 1972, et al.
(författare)
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Cloning of somatolactin alpha, beta forms and the somatolactin receptor in Atlantic salmon: Seasonal expression profile in pituitary and ovary of maturing female broodstock
- 2008
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Ingår i: Reproductive Biology and Endocrinology. - : Springer Science and Business Media LLC. - 1477-7827. ; 6:42
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Tidskriftsartikel (refereegranskat)abstract
- Background Somatolactin (Sl) is a fish specific adenohypophyseal peptide hormone related to growth hormone (Gh). Some species, including salmonids, possess two forms: Sl alpha and Sl beta. The somatolactin receptor (slr) is closely related to the growth hormone receptor (ghr). Sl has been ascribed many physiological functions, including a role in sexual maturation. In order to clarify the role of Sl in the sexual maturation of female Atlantic salmon (Salmo salar), the full length cDNAs of slr, Sl alpha and Sl beta were cloned and their expression was studied throughout a seasonal reproductive cycle using real-time quantitative PCR (RTqPCR). Methods Atlantic salmon Sl alpha, Sl beta and slr cDNAs were cloned using a PCR approach. Gene expression of Sl alpha, SL beta and slr was studied using RTqPCR over a 17 month period encompassing pre-vitellogenesis, vitellogenesis, ovulation and post ovulation in salmon females. Histological examination of ovarian samples allowed for the classification according to the degree of follicle maturation into oil drop, primary, secondary or tertiary yolk stage. Results The mature peptide sequences of Sl alpha, Sl beta and slr are highly similar to previously cloned salmonid forms and contained the typical motifs. Phylogenetic analysis of Atlantic salmon Sl alpha and Sl beta shows that these peptides group into the two Sl clades present in some fish species. The Atlantic salmon slr grouped with salmonid slr amongst so-called type I ghr. An increase in pituitary Sl alpha and Sl beta transcripts before and during spawning, with a decrease post-ovulation, and a constant expression level of ovarian slr were observed. There was also a transient increase in Sl alpha and Sl beta in May prior to transfer from seawater to fresh water and ensuing fasting. Conclusion The up-regulation of Sl alpha and Sl beta during vitellogenesis and spawning, with a subsequent decrease post-ovulation, supports a role for Sl during gonadal growth and spawning. Sl could also be involved in calcium/phosphate mobilization associated with vitellogenesis or have a role in energy homeostasis associated with lipolysis during fasting. The up-regulation of both Sl alpha and Sl beta prior to fasting and freshwater transfer, suggests a role for Sl linked to reproduction that may be independent of the maturation induced fasting.
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| 3. |
- Benedet Perea, Susana, 1972
(författare)
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Growth hormone and somatolactin function during sexual maturation of female Atlantic salmon
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background and aims: The growth hormone-insulin-like growth factor I (GH-IGF-I) system is known to act during sexual maturation of female salmonids, but the specific roles are not known. Somatolactin (SL) is a pituitary hormone closely related to GH and is only found in fish. In some species, including salmonids, there are two forms, SLa and SLß. The SL receptor (SLR) has recently been cloned and phylogenetic analysis shows that it is similar to previously cloned GH receptors (GHRs) of non-salmonids. The ligand-specificity of the GHR/SLR is unclear. Little is known about the role of the SLs in sexual maturation of fish. The aim of this thesis has been to increase our knowledge about the regulatory role(s) of both the GH-IGF-I system and of SLs during sexual maturation in female Atlantic salmon. Methods: The cDNA sequences of Atlantic salmon GHRs (two isoforms), SLR, as well as SLa and SLß were obtained with the goals of carrying out a phylogenetic analysis, and of developing molecular tools for analysis of mRNA levels using real time quantitative PCR (RTqPCR). The roles of GH, IGF-I and SL were examined in a 17-month long study on one sea winter Atlantic salmon females. mRNA expression levels of ovarian components of the GH-IGF-I system and SLR and pituitary GH, SLa and SLß were studied by RTqPCR. Levels of GH and IGF-I in plasma, and of GH in the pituitary were measured by radio-immunoassay. Results and Conclusions: The phylogenetic analysis (Paper I and II) of the cloned sequences reveals the placement of Atlantic salmon GHR in the GHR type II clade and SLR in the controversial GHR type I clade (putative SLRs). Concurrent analyses of pituitary GH mRNA levels, GH protein and plasma GH in the same individual fish demonstrates the complex dynamics of the GH system, which is inhibited by a continuous light. Papers III and IV confirm that there is an active GH-IGF-I-gonad axis in the female Atlantic salmon that appears to be functional at the start of exogenous vitellogenesis, final oocyte growth, spawning and possibly during postovulatory events. Evidence has been found for a photoperiod-driven GH-system activation which is initiated in January with stimulation of GH secretion from pituitary somatotropes. The role of this activation of the GH system in late winter/early spring appears to be the reversal of a prior plasma IGF-I and ovarian IGF-I mRNA downregulation driven by an unknown factor(s). This downregulation in IGF-I is thought to inhibit somatic cell proliferation. The activation of the GH-IGF-I-gonadal system also appears to limit energy allocation to gonadal growth. This series of events involving the GH-IGF-I system appears to take place during the so-called spring window of opportunity and it is the first time this has been described. The GH-IGF-I system also appears to have an important role during final oocyte growth, spawning and post-spawning events. SLa and SLß are both actively regulated during sexual maturation and could have several roles, such as signaling the status of visceral fat reserves during the spring window of opportunity, signaling lipid metabolic status before the onset of anorexia, involvement in Ca mobilization during vitellogenesis and/or control of lipid metabolism in lieu of GH during the final stages of oocyte growth.
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| 4. |
- Wargelius, A., et al.
(författare)
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A peak in gh-receptor expression is associated with growth activation in Atlantic salmon vertebrae, while upregulation of igf-I receptor expression is related to increased bone density
- 2005
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 142:1-2, s. 163-168
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Tidskriftsartikel (refereegranskat)abstract
- Growth hormone (GH) and insulin-like growth factor-I (IGF-I) play major roles in the endocrine regulation of fish growth, but their interdependency and mode of action has not been well elucidated. The GH-IGF-I system is essential for normal vertebral growth in mouse, but this has not been Studied in fish. To study the interplay between GH, IGF-I, and their receptors, postsmolt Atlantic salmon were studied during spring growth (January June 2003). From January to June, fish were sampled regularly for plasma and vertebral bone. The vertebra was collected from the same anterior-posterior position. The growth hormone receptor (ghr) (There is no determined nomenclature of salmon genes but we stick to the nomenclature which is consequent for zebrafish, where all,gene names are named with small letters and in italic.) expression in the vertebrae peaked in the end of February coinciding with high levels of plasma GH and IGF-I, and an increase of vertebral growth rate. From April to June, plasma IGF-I levels decreased together with ghr expression in the vertebrae, while plasma GH did not decrease. In May and June, expression of the igf-I receptor (igf-Ir) increased 4- to 5-fold, which coincided with an increase in bone density. The changes seen in gene expression of the IGF-I and GH receptors suggest that these hormones are involved in vertebral growth and bone density. © 2005 Elsevier Inc. All rights reserved.
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