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Gonigam RL, Weis KE, Ge X, Yao B, Zhang Q, Raetzman LT. Characterization of Somatotrope Cell Expansion in Response to GHRH in the Neonatal Mouse Pituitary. Endocrinology 2023; 164:bqad131. [PMID: 37616545 PMCID: PMC11009787 DOI: 10.1210/endocr/bqad131] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 07/25/2023] [Accepted: 08/22/2023] [Indexed: 08/26/2023]
Abstract
In humans and mice, loss-of-function mutations in growth hormone-releasing hormone receptor (GHRHR) cause isolated GH deficiency. The mutant GHRHR mouse model, GhrhrLit/Lit (LIT), exhibits loss of serum GH, but also fewer somatotropes. However, how loss of GHRH signaling affects expansion of stem and progenitor cells giving rise to GH-producing cells is unknown. LIT mice and wild-type littermates were examined for differences in proliferation and gene expression of pituitary lineage markers by quantitative reverse transcription polymerase chain reaction and immunohistochemistry at postnatal day 5 (p5) and 5 weeks. At p5, the LIT mouse shows a global decrease in pituitary proliferation measured by proliferation marker Ki67 and phospho-histone H3. This proliferative defect is seen in a pituitary cell expressing POU1F1 with or without GH. SOX9-positive progenitors show no changes in proliferation in p5 LIT mice. Additionally, the other POU1F1 lineage cells are not decreased in number; rather, we observe an increase in lactotrope cell population as well as messenger RNA for Tshb and Prl. In the 5-week LIT pituitary, the proliferative deficit in POU1F1-expressing cells observed neonatally persists, while the number and proliferative proportion of SOX9 cells do not appear changed. Treatment of cultured pituitary explants with GHRH promotes proliferation of POU1F1-expressing cells, but not GH-positive cells, in a mitogen-activated protein kinase-dependent manner. These findings indicate that hypothalamic GHRH targets proliferation of a POU1F1-positive cell, targeted to the somatotrope lineage, to fine tune their numbers.
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Affiliation(s)
- Richard L Gonigam
- Department of Molecular and Integrative Physiology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Karen E Weis
- Department of Molecular and Integrative Physiology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Xiyu Ge
- Department of Molecular and Integrative Physiology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Boyuan Yao
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai 200031, China
- National Center for Neurological Disorders, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai 200031, China
| | - Qilin Zhang
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai 200031, China
- National Center for Neurological Disorders, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai 200031, China
| | - Lori T Raetzman
- Department of Molecular and Integrative Physiology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
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Sol CM, Gaylord A, Santos S, Jaddoe VWV, Felix JF, Trasande L. Fetal exposure to phthalates and bisphenols and DNA methylation at birth: the Generation R Study. Clin Epigenetics 2022; 14:125. [PMID: 36217170 PMCID: PMC9552446 DOI: 10.1186/s13148-022-01345-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 09/23/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Phthalates and bisphenols are non-persistent endocrine disrupting chemicals that are ubiquitously present in our environment and may have long-lasting health effects following fetal exposure. A potential mechanism underlying these exposure-outcome relationships is differential DNA methylation. Our objective was to examine the associations of maternal phthalate and bisphenol concentrations during pregnancy with DNA methylation in cord blood using a chemical mixtures approach. METHODS This study was embedded in a prospective birth cohort study in the Netherlands and included 306 participants. We measured urine phthalates and bisphenols concentrations in the first, second and third trimester. Cord blood DNA methylation in their children was processed using the Illumina Infinium HumanMethylation450 BeadChip using an epigenome-wide association approach. Using quantile g-computation, we examined the association of increasing all mixture components by one quartile with cord blood DNA methylation. RESULTS We did not find evidence for statistically significant associations of a maternal mixture of phthalates and bisphenols during any of the trimesters of pregnancy with DNA methylation in cord blood (all p values > 4.01 * 10-8). However, we identified one suggestive association (p value < 1.0 * 10-6) of the first trimester maternal mixture of phthalates and bisphenols and three suggestive associations of the second trimester maternal mixture of phthalates and bisphenols with DNA methylation in cord blood. CONCLUSIONS Although we did not identify genome-wide significant results, we identified some suggestive associations of exposure to a maternal mixture of phthalates and bisphenols in the first and second trimester with DNA methylation in cord blood that need further exploration in larger study samples.
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Affiliation(s)
- Chalana M. Sol
- grid.5645.2000000040459992XThe Generation R Study Group, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands ,grid.5645.2000000040459992XDepartment of Pediatrics, Erasmus MC – Sophia Children’s Hospital, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Abigail Gaylord
- grid.137628.90000 0004 1936 8753Department of Population Health, New York University School of Medicine, 403 East 34th Street, Room 115, New York City, NY 10016 USA
| | - Susana Santos
- grid.5645.2000000040459992XThe Generation R Study Group, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands ,grid.5645.2000000040459992XDepartment of Pediatrics, Erasmus MC – Sophia Children’s Hospital, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Vincent W. V. Jaddoe
- grid.5645.2000000040459992XThe Generation R Study Group, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands ,grid.5645.2000000040459992XDepartment of Pediatrics, Erasmus MC – Sophia Children’s Hospital, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Janine F. Felix
- grid.5645.2000000040459992XThe Generation R Study Group, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands ,grid.5645.2000000040459992XDepartment of Pediatrics, Erasmus MC – Sophia Children’s Hospital, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Leonardo Trasande
- Department of Population Health, New York University School of Medicine, 403 East 34th Street, Room 115, New York City, NY, 10016, USA. .,Department of Pediatrics, New York University School of Medicine, 403 East 34th Street, Room 115, New York City, NY, 10016, USA. .,Department of Environmental Medicine, New York University School of Medicine, 403 East 34th Street, Room 115, New York City, NY, 10016, USA. .,New York Wagner School of Public Service, New York City, NY, 10016, USA. .,New York University Global Institute of Public Health, New York City, NY, 10016, USA.
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3
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Phoenixin participated in regulation of food intake and growth in spotted scat, Scatophagus argus. Comp Biochem Physiol B Biochem Mol Biol 2018; 226:36-44. [DOI: 10.1016/j.cbpb.2018.07.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2018] [Revised: 07/22/2018] [Accepted: 07/30/2018] [Indexed: 12/19/2022]
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Sundralingam T, Tennekoon KH, de Silva S, De Silva S, Hewage AS. Pathogenic and likely pathogenic genetic alterations and polymorphisms in growth hormone gene (GH1) and growth hormone releasing hormone receptor gene (GHRHR) in a cohort of isolated growth hormone deficient (IGHD) children in Sri Lanka. Growth Horm IGF Res 2017; 36:22-29. [PMID: 28910730 DOI: 10.1016/j.ghir.2017.08.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2017] [Revised: 08/28/2017] [Accepted: 08/31/2017] [Indexed: 11/21/2022]
Abstract
OBJECTIVE Genetic alterations in GH1 and GHRHR genes are known to cause isolated growth hormone deficiency (IGHD). Of these, GHRHR codon 72 mutation has been reported to be highly prevalent in the Indian subcontinent, but among Sri Lankans its prevalence was low compared to reports from neighboring countries. The present study was therefore carried out to identify genetic alterations in the GH1 gene and rest of the GHRHR gene in a cohort of Sri Lankan IGHD patients who tested negative for GHRHR codon 72 mutation. METHODS Fifty five IGHD children negative for codon 72 (GHRHR) mutation were screened for gross GH1 gene deletion by polymerase chain reaction (PCR) and restriction fragment length polymorphism technique. The coding, intronic and promoter regions of the GH1 gene were sequenced in children who were negative for GH1 deletion (N=53). In a subset (N=40), coding, flanking intronic and promoter regions of the GHRHR gene were screened by single strand conformation polymorphism/sequencing. Identified coding region and intronic variants were subjected to in silico analysis to ascertain pathogenicity. Family members available were screened for the significant variants observed in the index child. RESULTS Gross GH1 gene deletions, 6.7kb and 7.0kb were observed in one child each. One novel and 24 reported single nucleotide variants (SNVs) were observed in the GH1 gene and its promoter. These included one reported pathogenic splice site mutation (c.172-2A>T) and one reported likely pathogenic missense mutation (c.406G>T). One large novel deletion of 5875 base pairs that included exon 1, one likely pathogenic novel SNV (c.211G>T) and 18 reported SNVs were observed in the GHRHR gene. Fourteen variants observed were of uncertain significance (8 in GH1 and 6 in GHRHR), twenty three variants were likely benign (11 in GH1 and 12 in GHRHR) and four variants were benign (4 in GH1 and none in GHRHR). CONCLUSION In a cohort of IGHD children, six pathogenic or likely pathogenic genetic alterations of either GH1 gene or GHRHR gene were found. These affected a total of six children. Pathogenic status of four of these had been reported in the literature. Novel SNV in the GHRHR gene was predicted to be pathogenic through in silico analysis. The large novel deletion is likely to be pathogenic as it included exon 1 of GHRHR gene. Analysis of other genes will be needed to ascertain the genetic cause of IGHD in the remaining children.
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Affiliation(s)
- Tharmini Sundralingam
- Institute of Biochemistry, Molecular Biology and Biotechnology, 90, Cumaratunga Munidasa Mawatha, Colombo 03, Sri Lanka
| | - Kamani Hemamala Tennekoon
- Institute of Biochemistry, Molecular Biology and Biotechnology, 90, Cumaratunga Munidasa Mawatha, Colombo 03, Sri Lanka.
| | - Shamya de Silva
- Department of Paediatrics, Faculty of Medicine, PO Box 271, Kynsey Road, Colombo 08, Sri Lanka; Lady Ridgeway Hospital, Dr. Danister de Silva Mawatha, Colombo 08, Sri Lanka
| | - Sumadee De Silva
- Institute of Biochemistry, Molecular Biology and Biotechnology, 90, Cumaratunga Munidasa Mawatha, Colombo 03, Sri Lanka.
| | - Asanka Sudeshini Hewage
- Institute of Biochemistry, Molecular Biology and Biotechnology, 90, Cumaratunga Munidasa Mawatha, Colombo 03, Sri Lanka.
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Bentz AB, Sirman AE, Wada H, Navara KJ, Hood WR. Relationship between maternal environment and DNA methylation patterns of estrogen receptor alpha in wild Eastern Bluebird (Sialia sialis) nestlings: a pilot study. Ecol Evol 2016; 6:4741-52. [PMID: 27547309 PMCID: PMC4979703 DOI: 10.1002/ece3.2162] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 04/11/2016] [Accepted: 04/13/2016] [Indexed: 12/18/2022] Open
Abstract
There is mounting evidence that, across taxa, females breeding in competitive environments tend to allocate more testosterone to their offspring prenatally and these offspring typically have more aggressive and faster‐growing phenotypes. To date, no study has determined the mechanisms mediating this maternal effect's influence on offspring phenotype. However, levels of estrogen receptor alpha (ERα) gene expression are linked to differences in early growth and aggression; thus, maternal hormones may alter gene regulation, perhaps via DNA methylation, of ERα in offspring during prenatal development. We performed a pilot study to examine natural variation in testosterone allocation to offspring through egg yolks in wild Eastern Bluebirds (Sialia sialis) in varying breeding densities and percent DNA methylation of CG dinucleotides in the ERα promoter in offspring brain regions associated with growth and behavior. We hypothesized that breeding density would be positively correlated with yolk testosterone, and prenatal exposure to maternal‐derived yolk testosterone would be associated with greater offspring growth and decreased ERα promoter methylation. Yolk testosterone concentration was positively correlated with breeding density, nestling growth rate, and percent DNA methylation of one out of five investigated CpG sites (site 3) in the diencephalon ERα promoter, but none in the telencephalon (n = 10). Percent DNA methylation of diencephalon CpG site 3 was positively correlated with growth rate. These data suggest a possible role for epigenetics in mediating the effects of the maternal environment on offspring phenotype. Experimentally examining this mechanism with a larger sample size in future studies may help elucidate a prominent way in which animals respond to their environment. Further, by determining the mechanisms that mediate maternal effects, we can begin to understand the potential for the heritability of these mechanisms and the impact that maternal effects are capable of producing at an evolutionary scale.
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Affiliation(s)
- Alexandra B Bentz
- Poultry Science Department University of Georgia 203 Poultry Science Bldg. Athens Georigia 30602
| | - Aubrey E Sirman
- Department of Biological Sciences Auburn University 101 Life Science Building Auburn Alabama 36849
| | - Haruka Wada
- Department of Biological Sciences Auburn University 101 Life Science Building Auburn Alabama 36849
| | - Kristen J Navara
- Poultry Science Department University of Georgia 203 Poultry Science Bldg. Athens Georigia 30602
| | - Wendy R Hood
- Department of Biological Sciences Auburn University 101 Life Science Building Auburn Alabama 36849
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6
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Arman A, Dündar BN, Çetinkaya E, Erzaim N, Büyükgebiz A. Novel growth hormone-releasing hormone receptor gene mutations in Turkish children with isolated growth hormone deficiency. J Clin Res Pediatr Endocrinol 2014; 6:202-8. [PMID: 25541890 PMCID: PMC4293654 DOI: 10.4274/jcrpe.1518] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
OBJECTIVE Isolated growth hormone deficiency (IGHD) is defined as a medical condition associated with growth failure due to insufficient production of GH or lack of GH action. Mutations in the gene encoding for GH-releasing hormone receptor (GHRHR) have been detected in patients with IGHD type IB. However, genetic defects on GHRHR causing IGHD in the Turkish population have not yet been reported. To identify mutations on GHRHR gene in a population of Turkish children with IGHD. METHODS Ninety-six Turkish children with IGHD were included in this study. Exon1-13 and exon/intron boundaries of GHRHR were amplified by suitable primers. The polymerase chain reaction products for GHRHR gene were sequenced with primers. RESULTS We analyzed the GHRHR gene for mutations in ninety-six patients with IGHD based on sequence results. We identified novel p.K264E, p.S317T, p.S330L, p.G369V, p.T257A and C base insertion on position 380 (c.380inserC) mutations. In 5 of the patients, the mutation was homozygote and in 1-heterozygote (p.S317T). CONCLUSION Six new missense mutations and one first case of insertion mutations for the GHRHR gene are reported.
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Affiliation(s)
- Ahmet Arman
- Marmara University Faculty of Medicine, Department of Medical Genetics, İstanbul, Turkey. E-ma-il:
| | - Bumin Nuri Dündar
- Katip Çelebi University Faculty of Medicine, Department of Pediatric Endocrinology, İzmir, Turkey
| | | | - Nilüfer Erzaim
- Yeditepe University Faculty of Medicine, Department of Genetics and Bioengineering, İstanbul, Turkey
| | - Atilla Büyükgebiz
- Bilim University Faculty of Medicine, Department of Pediatric Endocrinology, İstanbul, Turkey
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7
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Kale S, Budyal S, Kasaliwal R, Shivane V, Raghavan V, Lila A, Bandgar T, Shah N. A novel gross indel in the growth hormone releasing hormone receptor gene of Indian IGHD patients. Growth Horm IGF Res 2014; 24:227-232. [PMID: 25153028 DOI: 10.1016/j.ghir.2014.07.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 07/29/2014] [Indexed: 11/20/2022]
Abstract
CONTEXT Cohort specific mutations in the growth hormone (GH1) and growth hormone-releasing hormone receptor (GHRHR) genes have been reported worldwide in isolated growth hormone deficiency (IGHD) patients. However, limited data is available on ethnically diverse Indian IGHD patients. OBJECTIVE The aim of the study was to find GH1 and GHRHR gene mutations in Indian IGHD patients from two unrelated non-consanguineous families. DESIGN The 5' and 3' untranslated regions (UTRs) and coding regions with splice sites of the GH1 and GHRHR genes were sequenced for all patients (n=6). Family members and 20 controls were evaluated for the sequence variants identified in the index patients. Online bioinformatics tools were used to confirm mutations and their pathogenicity. RESULTS GHRHR gene mutations were observed in all patients. Interestingly, a novel indel g.30999250_31006943delinsAGAGATCCA was observed in both the unrelated families. Three patients were homozygous for the novel indel, two were homozygous for the previously reported p.E72X mutation and one was compound heterozygous with both the mutations (indel and p.E72X) in the GHRHR gene. The novel indel has resulted in the loss of 5' regulatory region and exon 1 of the GHRHR gene impairing the GHRHR expression. All the normal family members were heterozygous either for the indel or p.E72X mutation. None of the patients had GH1 gene mutations. CONCLUSIONS We describe a novel gross indel in the GHRHR gene resulting in the loss of 5' regulatory region and GHRHR exon 1 in four IGHD IB patients from two unrelated non-consanguineous Indian families.
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Affiliation(s)
- Shantanu Kale
- Department of Endocrinology, Seth G.S. Medical College, K.E.M. Hospital, Parel, Mumbai 400012, India.
| | - Sweta Budyal
- Department of Endocrinology, Seth G.S. Medical College, K.E.M. Hospital, Parel, Mumbai 400012, India
| | - Rajeev Kasaliwal
- Department of Endocrinology, Seth G.S. Medical College, K.E.M. Hospital, Parel, Mumbai 400012, India
| | - Vyankatesh Shivane
- Department of Endocrinology, Seth G.S. Medical College, K.E.M. Hospital, Parel, Mumbai 400012, India
| | - Vijaya Raghavan
- Department of Endocrinology, Seth G.S. Medical College, K.E.M. Hospital, Parel, Mumbai 400012, India
| | - Anurag Lila
- Department of Endocrinology, Seth G.S. Medical College, K.E.M. Hospital, Parel, Mumbai 400012, India
| | - Tushar Bandgar
- Department of Endocrinology, Seth G.S. Medical College, K.E.M. Hospital, Parel, Mumbai 400012, India
| | - Nalini Shah
- Department of Endocrinology, Seth G.S. Medical College, K.E.M. Hospital, Parel, Mumbai 400012, India
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A 5'UTR SNP of GHRHR locus is associated with body weight and average daily gain in Chinese cattle. Mol Biol Rep 2012; 39:10469-73. [PMID: 23053950 DOI: 10.1007/s11033-012-1927-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 10/01/2012] [Indexed: 10/27/2022]
Abstract
Growth hormone-releasing hormone receptor (GHRHR) has important functions in the regulation of the growth hormone axis and the development and proliferation of pituitary somatotropes. Moreover, some mutations in mouse GHRHR can induce the dwarfism. The objective of this paper is to reveal the association of GHRHR with growth traits in three Chinese cattle breeds, including Nanyang cattle (NY, 220), Qinchuan cattle (QC, 114), and Jiaxian cattle (JX, 142). A novel single nucleotide polymorphism (NM_181020:c.102C>T) in 5'UTR of GHRHR was identified using PCR-SSCP and DNA sequencing. The frequency of NM_181020:c.102C allele ranged from 0.926 to 0.956. We found that the locus was significantly associated with NY cattle's body weight (BW) of 6 months, with average daily gain (ADG) of 0-6 months, and as well as with ADG of 6-12 months (p < 0.05). The data suggested that the polymorphism (NM_181020:c.102C>T) of the GHRHR could be a molecular marker candidate for breeding of NY cattle in favor of BW.
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Carlomagno Y, Salerno M, Vivenza D, Capalbo D, Godi M, Mellone S, Tiradani L, Corneli G, Momigliano-Richiardi P, Bona G, Giordano M. A novel recessive splicing mutation in the POU1F1 gene causing combined pituitary hormone deficiency. J Endocrinol Invest 2009; 32:653-8. [PMID: 19498317 DOI: 10.1007/bf03345736] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND Mutations in the gene encoding the pituitary transcription factor POU1F1 (Pit-1, pituitary transcription factor-1) have been described in combined pituitary hormone deficiency (CPHD). AIM The aim of this study was the characterisation of the molecular defect causing CPHD in a patient born to consanguineous parents. SUBJECT AND METHODS The case of a 12.5-yr-old girl presenting with severe growth failure at diagnosis (-3 SD score at 3 months) and deficiency of GH, PRL, and TSH was investigated for the presence of POU1F1 gene mutations by denaturing high performance liquid chromatography analysis. RESULTS A novel mutation adjacent to the IVS2 splicing acceptor site (IVS2-3insA) was identified in the patient at the homozygous state. Analysis of patient's lymphocyte mRNA and an in vitro splicing assay revealed the presence of 2 aberrant splicing products: a) deletion of the first 71 nucleotides of exon 3, altering the open reading frame and generating a premature stop codon, b) total exon 3 skipping resulting in an in frame deleted mRNA encoding a putative protein lacking part of the transactivation domain and of the POUspecific homeodomain. Notably, the patient's relatives heterozygous for the mutation had PRL levels under the normal range with no evident clinical symptoms. CONCLUSIONS The IVS2- 3insAmutation, responsible for CPHD at the homozygous state, causes the presence of 2 aberrant splicing products encoding non-functional products. In the heterozygotes one normal allele might not guarantee a complete pituitary function.
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Affiliation(s)
- Y Carlomagno
- Laboratory of Human Genetics, Department of Medical Sciences, Eastern Piedmont University and Interdisciplinary Research Center on Autoimmune Diseases, 28100 Novara, Italy
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McElvaine AT, Korytko AI, Kilen SM, Cuttler L, Mayo KE. Pituitary-Specific Expression and Pit-1 Regulation of the Rat Growth Hormone-Releasing Hormone Receptor Gene. Mol Endocrinol 2007; 21:1969-83. [PMID: 17536003 DOI: 10.1210/me.2007-0116] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The GHRH receptor is expressed in the somatotroph cell of the anterior pituitary, where it functions to mediate GHRH-stimulated GH release. To study pituitary and somatotroph cell-specific expression of this gene, a transgenic mouse model and complementary cell culture experiments were developed. The activity of the 1.6-kb proximal rat GHRH receptor promoter was examined in vivo by generating transgenic mice with the promoter directing expression of a luciferase reporter. The promoter directs tissue-specific expression; luciferase is highly expressed in the pituitary but absent from 14 other tissues. Immunocytochemistry experiments show that transgene expression is targeted to GH-expressing somatotroph cells. The transgene is 5-fold more highly expressed in males than females, and there is an increase in transgene expression leading up to the onset of puberty. The 1.6-kb promoter was further examined in cell culture experiments, which revealed that the promoter is selectively activated in pituitary cells and that promoter-reporter expression in nonpituitary cells can be enhanced by the pituitary-specific transcription factor Pit-1. EMSAs identified 10 short regions that specifically bind Pit-1 with highly variable relative affinities. The highest affinity site was previously identified and is required for Pit-1 activation of the promoter. Four additional sites contribute to Pit-1 regulation of the promoter and are important to achieving full activation of the gene. The results show that the 1.6-kb promoter is sufficient to direct tissue- and cell-specific expression in vivo and is regulated by Pit-1.
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Affiliation(s)
- Allison T McElvaine
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Hogan 4-112, Evanston, Illinois 60208, USA
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11
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Porter TE, Ellestad LE, Fay A, Stewart JL, Bossis I. Identification of the chicken growth hormone-releasing hormone receptor (GHRH-R) mRNA and gene: regulation of anterior pituitary GHRH-R mRNA levels by homologous and heterologous hormones. Endocrinology 2006; 147:2535-43. [PMID: 16469800 DOI: 10.1210/en.2005-1534] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
GHRH stimulates GH secretion in chickens as in mammals. However, nothing is known about the chicken GHRH receptor (GHRH-R). Here we report the cDNA sequence of chicken GHRH-R. Comparison of the cDNA sequence with the chicken genome localized the GHRH-R gene to chicken chromosome 2 and indicated that the chicken GHRH-R gene consists of 13 exons. Expression of all exons was confirmed by RT-PCR amplification of pituitary mRNA. The amino acid sequence predicted by the GHRH-R cDNA is homologous to that in other vertebrates and contains seven transmembrane domains and a conserved hormone-binding domain. The predicted size of the GHRH-R protein (48.9 kDa) was confirmed by binding of (125)I-GHRH to chicken pituitary membranes and SDS-PAGE. GHRH-R mRNA was readily detected by RT-PCR in the pituitary but not in the hypothalamus, total brain, lung, adrenal, ovary, or pineal gland. Effects of corticosterone (CORT), GHRH, ghrelin, pituitary adenylate cyclase-activating peptide, somatostatin (SRIF), and TRH on GHRH-R and GH gene expression were determined in cultures of chicken anterior pituitary cells. GHRH-R and GH mRNA levels were determined by quantitative real-time RT-PCR. Whereas all treatments affected levels of GH mRNA, only CORT, GHRH, and SRIF significantly altered GHRH-R mRNA levels. GHRH-R gene expression was modestly increased by GHRH and suppressed by SRIF at 4 h, and CORT dramatically decreased levels of GHRH-R mRNA at 72 h. We conclude that adrenal glucocorticoids may substantially impact pituitary GH responses to GHRH in the chicken through modulation of GHRH-R gene expression.
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MESH Headings
- Amino Acid Sequence
- Animals
- Brain/embryology
- Cells, Cultured
- Chickens
- Chromosome Mapping
- Computational Biology
- Cross-Linking Reagents/pharmacology
- DNA Primers/chemistry
- DNA, Complementary/metabolism
- Dose-Response Relationship, Drug
- Electrophoresis, Polyacrylamide Gel
- Exons
- Female
- Gene Expression Regulation
- Gene Library
- Hypothalamus/metabolism
- Introns
- Molecular Sequence Data
- Molecular Weight
- Phylogeny
- Protein Binding
- Protein Structure, Tertiary
- RNA, Messenger/metabolism
- Receptors, Neuropeptide/genetics
- Receptors, Neuropeptide/physiology
- Receptors, Pituitary Hormone-Regulating Hormone/genetics
- Receptors, Pituitary Hormone-Regulating Hormone/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Time Factors
- Tissue Distribution
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Affiliation(s)
- Tom E Porter
- Department of Animal and Avian Sciences, University of Maryland, College Park, 20742, USA
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12
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Wang CY, Wang Y, Li J, Leung FC. Expression profiles of growth hormone-releasing hormone and growth hormone-releasing hormone receptor during chicken embryonic pituitary development. Poult Sci 2006; 85:569-76. [PMID: 16553291 DOI: 10.1093/ps/85.3.569] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Growth hormone-releasing hormone (GHRH) and its receptor (GHRHR) have long been regarded as the critical molecules for the stimulation of growth hormone (GH) synthesis and release, as well as the regulation of pituitary somatotroph expansion in vertebrates. However, little is known about their expression in the embryonic pituitaries of birds. In this study, the full-length cDNA for chicken GHRHR was cloned from the chicken pituitary. It encodes 419 amino acids and shares high homology with that of the human, rat, and mouse. As in those in mammals, chicken GHRHR is predominantly expressed in the pituitary and weakly expressed in several extra-pituitary tissues including brain, pancreas, testis, and kidney, among 12 tissues examined. Using semiquantitative reverse transcription-PCR, we further examined the expression of GH, GHRH, and GHRHR during embryonic pituitary development. The expression of GHRHR on embryonic d 8 was much lower, but abundant expression was noticed as early as embryonic d 12. In contrast, the level of pituitary GHRH mRNA peaked on d 8 and declined sharply afterwards. Interestingly, unlike those of pituitary GHRH and GHRHR, the higher expression levels of GH appeared much later (from d 16 to 20). The differential expressions of GHRH, GHRHR, and GH in the developing embryonic pituitaries not only imply that pituitary-derived GHRH (or pituitary adenylate cyclase-activating polypeptide) and GHRHR may have a paracrine/autocrine role in the expansion of undifferentiated somatotroph precursor cells, but also suggest that GHRHR is likely to be involved in the somatotroph differentiation occurring at the later developmental stages.
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Affiliation(s)
- C Y Wang
- Department of Zoology, The University of Hong Kong, Hong Kong, China
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Ezzat S, Mader R, Fischer S, Yu S, Ackerley C, Asa SL. An essential role for the hematopoietic transcription factor Ikaros in hypothalamic-pituitary-mediated somatic growth. Proc Natl Acad Sci U S A 2006; 103:2214-9. [PMID: 16467156 PMCID: PMC1413703 DOI: 10.1073/pnas.0508565103] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Ikaros transcription factors play critical functions in the control of lymphohematopoiesis and immune regulation. Family members contain multiple zinc fingers that mediate DNA binding and homooligomerization or heterooligomerization. Ikaros is abundantly expressed in pituitary mammosomatotrophs, where it deacetylates histone 3 sites on the proximal growth hormone (GH) promoter to silence gene expression. Ikaros-null mice display stunted growth with reduced circulating levels of the GH target factor insulin-like growth factor I (IGF-I). Ikaros-deficient mice have small anterior pituitary glands with a disproportionately reduced somatotroph population. Systemic administration of GH results in increased IGF-I levels and enhanced somatic growth. In contrast, reconstitution with WT lymphocytes was not sufficient to rescue the stunted growth phenotype of Ikaros-deficient mice. Ikaros was identified in mouse hypothalamic arcuate nuclei, where it colocalized with GH-releasing hormone (GHRH); in contrast, Ikaros-null mice lack GHRH immunoreactivity in the hypothalamus. Overexpression of Ikaros enhanced GHRH promoter activity and induced endogenous GHRH gene expression. These findings unmask a wider role for Ikaros in the neuroendocrine system, highlighting a critical contribution to the development of the hypothalamic-pituitary somatotrophic axis.
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Affiliation(s)
- Shereen Ezzat
- *Department of Medicine, Mount Sinai Hospital
- The Freeman Centre for Endocrine Oncology and Ontario Cancer Institute, University of Toronto, 610 University Avenue, Toronto, ON, Canada M5G 2M9
- To whom correspondence should be addressed at:
Ontario Cancer Institute, University of Toronto, 610 University Avenue, 8-327, Toronto, ON, Canada, M5G-2M9. E-mail:
or
| | - Rene Mader
- Department of Pathology, University Health Network
- The Freeman Centre for Endocrine Oncology and Ontario Cancer Institute, University of Toronto, 610 University Avenue, Toronto, ON, Canada M5G 2M9
| | - Sandra Fischer
- Department of Pathology, University Health Network
- The Freeman Centre for Endocrine Oncology and Ontario Cancer Institute, University of Toronto, 610 University Avenue, Toronto, ON, Canada M5G 2M9
| | - ShunJiang Yu
- *Department of Medicine, Mount Sinai Hospital
- The Freeman Centre for Endocrine Oncology and Ontario Cancer Institute, University of Toronto, 610 University Avenue, Toronto, ON, Canada M5G 2M9
| | | | - Sylvia L. Asa
- Department of Pathology, University Health Network
- The Freeman Centre for Endocrine Oncology and Ontario Cancer Institute, University of Toronto, 610 University Avenue, Toronto, ON, Canada M5G 2M9
- To whom correspondence should be addressed at:
Ontario Cancer Institute, University of Toronto, 610 University Avenue, 8-327, Toronto, ON, Canada, M5G-2M9. E-mail:
or
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14
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Mulhall C, Hegele RA, Cao H, Tritchler D, Yaffe M, Boyd NF. Pituitary growth hormone and growth hormone-releasing hormone receptor genes and associations with mammographic measures and serum growth hormone. Cancer Epidemiol Biomarkers Prev 2006; 14:2648-54. [PMID: 16284391 DOI: 10.1158/1055-9965.epi-04-0374] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Mammographic density is a strong risk factor for breast cancer that is heritable and associated with blood levels of growth hormone and insulin-like growth factor-I (IGF-I). We tested single nucleotide polymorphisms (SNP) in pituitary growth hormone (GH1) and growth hormone-releasing hormone receptor (GHRHR) genes for an association with mammographic density, hormones of the growth hormone/IGF-I axis, and anthropometric variables. METHODS Mammograms from 348 women were measured using a computer-assisted method, blood collected, and DNA extracted. The SNPs genotyped were GH1 -57G>T, GH1 -75G >A, and GHRHR A57T. ANOVA and covariance were used to examine associations, adjusted for age, body mass index, ethnicity, and menopausal status, between each SNP and three measures of the mammogram: percent density, total dense area, and total nondense area. Similarly, the SNPs were tested for associations with serum growth hormone, IGF-I, IGFBP3, prolactin, and anthropometric variables. RESULTS GH1 -57G >T and GH1 -75G >A were both associated with percent density and total nondense area. GH1 -57T homozygotes had 5.2 more mean adjusted percent density than other subjects combined (P = 0.03) and 16.2 cm(2) (14.6%) less nondense area (P = 0.01). GH1 -75A homozygotes had 3.4 more percent density than subjects with at least one G allele (P = 0.04) and also had 32% higher serum growth hormone levels (P = 0.02). CONCLUSION We have found associations between mammographic density and two SNPs in the pituitary growth hormone gene, one of them also associated with serum growth hormone levels. These findings suggest that the GH1 gene may also influence breast cancer risk.
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Affiliation(s)
- Cara Mulhall
- Division of Epidemiology and Statistics, Ontario Cancer Institute, Room 10-415, 610 University Avenue, Toronto, Ontario, Canada M5G 2M9
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15
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Zhan X, Desiderio DM. Comparative proteomics analysis of human pituitary adenomas: current status and future perspectives. MASS SPECTROMETRY REVIEWS 2005; 24:783-813. [PMID: 15495141 DOI: 10.1002/mas.20039] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This article will review the published research on the elucidation of the mechanisms of pituitary adenoma formation. Mass spectrometry (MS) plays a key role in those studies. Comparative proteomics has been used with the long-term goal to locate, detect, and characterize the differentially expressed proteins (DEPs) in human pituitary adenomas; to identify tumor-related and -specific biomarkers; and to clarify the basic molecular mechanisms of pituitary adenoma formation. The methodology used for comparative proteomics, the current status of human pituitary proteomics studies, and future perspectives are reviewed. The methodologies that are used in comparative proteomics studies of human pituitary adenomas are readily exportable to other different areas of cancer research.
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Affiliation(s)
- Xianquan Zhan
- Charles B. Stout Neuroscience Mass Spectrometry Laboratory, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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16
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Yan M, Jones MEE, Hernandez M, Liu D, Simpson ER, Chen C. Functional modification of pituitary somatotropes in the aromatase knockout mouse and the effect of estrogen replacement. Endocrinology 2004; 145:604-12. [PMID: 14563698 DOI: 10.1210/en.2003-0646] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Available data on the influence of estradiol (E(2)) on GH levels remains controversial. A factor contributing to this uncertainty is a lack of knowledge of both E(2) action on somatotropes as well as the molecular mechanisms involved. In this study we investigated gene expression implicated in GH secretion in somatotropes derived from female aromatase knockout (ArKO) mice. In these mice E(2) production is blocked due to disruption of the Cyp19 gene encoding aromatase, the enzyme responsible for estrogen biosynthesis. The effect of E(2) replacement was also studied by in vivo treatment of mice with E(2) for 3 wk. It was demonstrated that somatotropes from ArKO mice had a low expression of GH, GH secretagogue receptor, GHRH receptor (GHRH-R), and pituitary-specific transcription factor (Pit-1). On the other hand, the somatotropes exhibited elevated expression of somatostatin receptors (sst1-5). Overall, these effects resulted in a reduction in GH secretion. E(2) replacement increased GHRH-R, Pit-1, and GH mRNA levels to 185%, 193%, and 157% and reduced the levels of sst1, sst2, sst4, and sst5 mRNA expression in ArKO mice, respectively. E(2) replacement did not affect the levels of pituitary estrogen (alpha and beta) and androgen receptor mRNA expression. It is concluded that the expression of important genes involved in GH synthesis in somatotropes of the female ArKO mouse are functionally down-regulated, and such a down-regulation is reversed to normal levels by E(2) replacement. The levels of GH secretagogue receptor, GHRH-R, and Pit-1 mRNA expression were also reduced, and sst1 and sst3 mRNA expression enhanced in aging ArKO and wild-type mice, resulting in a decrease in GH mRNA expression. It is suggested that aging is another important impact factor for the pituitary expression and regulation of GH mRNA in female mice.
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Affiliation(s)
- Ming Yan
- Prince Henry's Institute of Medical Research, Clayton, Victoria 3168, Australia
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Pang RTK, Lee LTO, Ng SSM, Yung WH, Chow BKC. CpG methylation and transcription factors Sp1 and Sp3 regulate the expression of the human secretin receptor gene. Mol Endocrinol 2003; 18:471-83. [PMID: 14645499 DOI: 10.1210/me.2003-0245] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The human secretin receptor (hSR) is an important glycoprotein receptor for regulating the secretion of pancreatic bicarbonate, water, and electrolytes. In this study we investigated the transcriptional regulation of the hSR gene. A minimal 106-bp promoter was identified, and it contains two GC boxes (GC box-A, -240 to -226; and GC box-B, -203 to -194, from the translation start site). EMSA and supershift analyses showed that both GC boxes interact with Sp1 and Sp3 transcription factors. Transient transfection in pancreas-derived human pancreatic ductule carcinoma (PANC)-1 and bovine pancreatic duct-1 cells showed that mutation of either GC box-A or -B reduced the promoter strength by 56-67%, whereas mutation of both GC boxes caused more than 90% reduction of promoter activity. Cotransfections of the hSR promoter with Sp1 and Sp3 expression vectors in Sp-deficient Drosophila SL-2 Schneider cells further demonstrated that the ratio of Sp1 to Sp3 is the key mechanism to modulate hSR gene expression. The methylation statuses of 27 CpG sites within the promoter region (-400 to -151 bp) were assessed in various human pancreas and liver cell lines. The hSR promoter is unmethylated (CAPAN-1, human pancreatic adenocarcinoma) or partially methylated (PANC-1 and HPAC, human pancreatic adenocarcinoma) in hSR-expressing cell lines but is completely methylated in hSR nonexpressing HepG2 cells. Methyltransferase inhibitor 5-aza-2'deoxycytidine increased hSR gene expression level in PANC-1 cells and induced hSR gene expression in HepG2 cells. Together, our study shows that, in addition to Sp1 and Sp3, promoter methylation also plays a role in the regulation of hSR gene expression.
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Affiliation(s)
- Ronald Ting-Kai Pang
- Department of Zoology, University of Hong Kong, Special Administrate Region, People's Republic of China
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Mohammad HP, Abbud RA, Parlow AF, Lewin JS, Nilson JH. Targeted overexpression of luteinizing hormone causes ovary-dependent functional adenomas restricted to cells of the Pit-1 lineage. Endocrinology 2003; 144:4626-36. [PMID: 12960102 DOI: 10.1210/en.2003-0357] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The majority of pituitary adenomas in humans are nonmetastasizing, monoclonal neoplasms that occur in approximately 20% of the general population. Their development has been linked to a combination of extrinsic factors and intrinsic defects. We now demonstrate with transgenic mice that targeted and chronic overexpression of LH causes ovarian hyperstimulation and subsequent hyperproliferation of Pit-1-positive cells that culminates in the appearance of functional pituitary adenomas ranging from focal to multifocal expansion of lactotropes, somatotropes, and thyrotropes. Tumors fail to develop in ovariectomized mice, indicating that contributions from the ovary are necessary for adenoma development. Although the link between chronic ovarian hyperstimulation and PRL-secreting adenomas was expected, the involvement of somatotropes and thyrotropes was surprising and suggests that multiple ovarian hormones may contribute to this unusual pathological consequence. In support of this idea, we have found that ovariectomy followed by estrogen replacement results in the expansion of lactotropes selectively in LH overexpressing mice, but not somatotropes and thyrotropes. Collectively, these data indicate that estrogen is sufficient for the formation of lactotrope adenomas only in animals with a hyperstimulated ovary, whereas the appearance of GH- and TSH-secreting adenomas depends on multiple ovarian hormones. Together, our data expand current models of pituitary tumorigenesis by suggesting that chronic ovarian hyperstimulation may underlie the formation of a subset of pituitary adenomas containing lactotropes, somatotropes, and thyrotropes.
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Affiliation(s)
- Helai P Mohammad
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106, USA
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19
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Affiliation(s)
- Karen Lin-Su
- Division of Pediatric Endocrinology, Weill Medical College of Cornell University, New York, USA
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20
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Kishimoto M, Okimura Y, Yagita K, Iguchi G, Fumoto M, Iida K, Kaji H, Okamura H, Chihara K. Novel function of the transactivation domain of a pituitary-specific transcription factor, Pit-1. J Biol Chem 2002; 277:45141-8. [PMID: 12200420 DOI: 10.1074/jbc.m202991200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Pit-1 stimulates the expression of growth hormone, prolactin, and thyrotropin beta subunit genes. Consequently, abnormality of the Pit-1 gene results in combined pituitary hormone deficiency (CPHD). In this study, we analyzed the function of Pit-1 with a mutation (proline to leucine at codon 24) in the transactivation domain, P24L, which has a normal POU domain important for binding to DNA, because this mutation had been reported in a patient with CPHD. We found that codon 24 proline in the transactivation domain as well as the POU domain of Pit-1 was crucial to recruit coactivator CREB-binding protein (CBP) in the cultured cells. P24L completely lost the responsiveness to cAMP to stimulate the expression of the Pit-1-targeted genes. Furthermore, CBP and Pit-1, but not P24L, markedly enhanced the expression of the Pit-1-targeted gene to cAMP, and adenovirus E1a that binds to CBP and abrogates its function blocked the induction by cAMP of Pit-1-stimulated gene transcription in the pituitary-derived GH3 cells. These results suggest that CBP and proline at codon 24 in the transactivation domain of Pit-1 are important for the cAMP-induced activation of Pit-1-targeted genes. However, P24L maintained basal transcriptional activity, suggesting that CBP is unlikely to be an essential coactivator for Pit-1.
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Affiliation(s)
- Masahiko Kishimoto
- Division of Endocrinology/Metabolism, Neurology and Hematology/Oncology, Department of Clinical Molecular Medicine, Kobe University Graduate School of Medicine, Kobe University School of Medicine, 7-10-2, Tomogaoka, Suma-ku, Kobe 654-0142, Japan
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21
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Ferrando S, Rodríguez J, Santos F, Weruaga A, Fernández M, Carbajo E, García E. Effects of growth hormone treatment on the pituitary expression of GHRH receptor mRNA in uremic rats. Kidney Int 2002; 62:775-9. [PMID: 12164859 DOI: 10.1046/j.1523-1755.2002.00513.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
BACKGROUND A decreased ability of pituitary cells to secrete growth hormone (GH) in response to growth hormone releasing hormone (GHRH) stimulation has been shown in young uremic rats. The aim of the current study was to examine the effect of uremia and GH treatment on pituitary GHRH receptor expression. METHODS Pituitary GHRH receptor mRNA levels were analyzed by RNase protection assay in young female rats made uremic by subtotal nephrectomy, either untreated (UREM) or treated with 10 IU/kg/day of GH (UREM-GH), and normal renal function animals fed ad libitum (SAL) or pair-fed with the UREM group (SPF). Rats were sacrificed 14 days after the second stage nephrectomy. RESULTS Renal failure was confirmed by concentrations (X +/- SEM) of serum urea nitrogen (mmol/L) and creatinine (micromol/L) in UREM (20 +/- 1 and 89.4 +/- 4.5) and UREM-GH (16 +/- 1 and 91.4 +/- 6.9) that were much higher (P < 0.001) than those of sham animals (SAL, 3 +/- 0 and 26.5 +/- 2.2; SPF, 4 +/- 0 and 26.5 +/- 2.1). UREM rats became growth retarded as shown by a daily longitudinal tibia growth rate below (P < 0.05) that observed in SAL animals (156 +/- 3 vs. 220 +/- 5 microm/day). GH treatment resulted in significant growth rate acceleration (213 +/- 6 microm/day). GHRH receptor mRNA levels were no different among the SAL (0.43 +/- 0.03), SPF (0.43 +/- 0.08) and UREM (0.44 +/- 0.04) groups, whereas UREM-GH rats had significantly higher values (0.72 +/- 0.07). CONCLUSIONS The status of pituitary GHRH receptor is not modified by nutritional deficit or by severe uremia causing growth retardation. By contrast, the growth promoting effect of GH administration is associated with stimulated GHRH receptor gene expression.
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Affiliation(s)
- Susana Ferrando
- School of Medicine, Hospital Central de Asturias, University of Oviedo, C/Julián Clavería 6, 33006 Oviedo, Asturias, Spain
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22
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Nogami H, Hiraoka Y, Matsubara M, Nonobe E, Harigaya T, Katayama M, Hemmi N, Kobayashi S, Mogi K, Aiso S, Kawamura K, Hisano S. A composite hormone response element regulates transcription of the rat GHRH receptor gene. Endocrinology 2002; 143:1318-26. [PMID: 11897688 DOI: 10.1210/endo.143.4.8710] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
To further elucidate the molecular mechanisms underlying the transcriptional regulation of the GHRH receptor (GHRH-R) gene, hormonal regulation of the promoter activity of this gene was examined. An approximately 3-kb genomic fragment spanning the promoter region of the gene was sequenced and the transcription start site was determined by RT-PCR and RNase protection assay. A major start site was localized at -105 (relative to the translation initiation codon, ATG), and a pit-1 binding sequence characteristic of pituitary specific genes was found at -155 to -146. Deletion and mutation studies demonstrated this site to be functional. In the presence of dexamethasone, the GHRH-R promoter (from -2935 to -11) directed luciferase expression in MtT-S cells, a somatotropic cell line, but not in the PC12 cells that normally do not express GHRH-R. While T(3), all trans-RA, and 9cis-RA alone weakly enhanced the reporter gene expression, each of these substances was found to act as a synergistic enhancer in the presence of dexamethasone. Additional deletion and mutation analyses demonstrated a functional RA response element at -1090 to -1074. Two functional glucocorticoid response elements and a T(3) response element were found in an 80-bp 5'-flanking sequence of the pit-1 site. Interestingly, it is suggested that the 6-bp half-site AGGACA (from -209 to -204) functions as a 3'-half-site of T(3) response element as well as a 5'-half-site of one of the glucocorticoid response elements.
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Affiliation(s)
- Haruo Nogami
- Department of Neuroendocrinology, Basic Medical Sciences, University of Tsukuba, Tsukuba 305-8575, Japan.
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Salvatori R, Thakker RV, Lopes MB, Fan X, Eswara JR, Ellison D, Lees P, Harding B, Yang I, Levine MA. Absence of mutations in the growth hormone (GH)-releasing hormone receptor gene in GH-secreting pituitary adenomas. Clin Endocrinol (Oxf) 2001; 54:301-7. [PMID: 11298081 DOI: 10.1046/j.1365-2265.2001.01213.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
OBJECTIVE GH-releasing hormone (GHRH) is a potent stimulator of somatotroph cell proliferation and GH secretion. GHRH acts via binding to a G-protein coupled receptor (GPCR) (GHRH-R), that activates adenylyl cyclase (AC) and increases growth and function of somatotroph cells. Indeed, a subset (30--40%) of somatotrophic adenomas contain somatic mutations of the GNAS1 gene that encodes the alpha subunit of the G-protein (G(s)alpha) that stimulates AC. As activating mutations of other GPCRs cause development of endocrine tumours, we hypothesized that somatic activating mutations of the GHRH-R might provide the molecular basis for somatotroph cell proliferation in a subset of human GH-secreting pituitary adenomas. DESIGN We analysed genomic DNA isolated from 26 somatotrophinomas, 17 of which lacked activating mutations in the GNAS1 gene. We individually amplified via polymerase chain reaction all 13 coding exons and the exon-intron boundaries of the GHRH-R gene. We used denaturing gradient gel electrophoresis to search for abnormalities in exons 1 through 11. Abnormally migrating bands were subjected to direct sequencing. Exons 12 and 13, encoding for the intracellular C-terminal domain, were subjected to direct sequencing. RESULTS Mutations were not detected in any of the tumours, but a rare polymorphism in codon 225 corresponding to the third transmembrane domain (V225I) was discovered. CONCLUSIONS GHRH-R mutations are absent or rare in somatotrophinomas, and other mechanisms must explain the somatotroph cell proliferation in the adenomas that lack activating mutations in the GNAS1 gene.
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Affiliation(s)
- R Salvatori
- Division of Endocrinology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
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Andersen B, Rosenfeld MG. POU domain factors in the neuroendocrine system: lessons from developmental biology provide insights into human disease. Endocr Rev 2001; 22:2-35. [PMID: 11159814 DOI: 10.1210/edrv.22.1.0421] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
POU domain factors are transcriptional regulators characterized by a highly conserved DNA-binding domain referred to as the POU domain. The structure of the POU domain has been solved, facilitating the understanding of how these proteins bind to DNA and regulate transcription via complex protein-protein interactions. Several members of the POU domain family have been implicated in the control of development and function of the neuroendocrine system. Such roles have been most clearly established for Pit-1, which is required for formation of somatotropes, lactotropes, and thyrotropes in the anterior pituitary gland, and for Brn-2, which is critical for formation of magnocellular and parvocellular neurons in the paraventricular and supraoptic nuclei of the hypothalamus. While genetic evidence is lacking, molecular biology experiments have implicated several other POU factors in the regulation of gene expression in the hypothalamus and pituitary gland. Pit-1 mutations in humans cause combined pituitary hormone deficiency similar to that found in mice deleted for the Pit-1 gene, providing a striking example of how basic developmental biology studies have provided important insights into human disease.
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Affiliation(s)
- B Andersen
- Department of Medicine, University of California, San Diego, La Jolla, 92093-0648, USA.
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25
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Nogami H, Matsubara M, Harigaya T, Katayama M, Kawamura K. Retinoic acids and thyroid hormone act synergistically with dexamethasone to increase growth hormone-releasing hormone receptor messenger ribonucleic acid expression. Endocrinology 2000; 141:4396-401. [PMID: 11108247 DOI: 10.1210/endo.141.12.7838] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The effects of all-trans-retinoic acid (RA), 9-cis-retinoic acid (9cRA), and thyroid hormone (T3) on GH-releasing hormone receptor (GHRH-R) messenger RNA (mRNA) expression were studied using ribonuclease protection assay in the fetal rat pituitary gland and in MtT/S cells, a clonal GH cell line derived from an estrogen-induced somatotropic tumor in the rat. Although RA (1 microM), 9cRA (1 microM), or T3 (1 nM) alone showed little effect on GHRH-R mRNA expression in the MtT/S cells, each of these substances was found to act synergistically with dexamethasone (DEX; 500 nM) to increase GHRH-R mRNA expression. The effects of RAs and T3 were dose dependent, with maximum effects observed at 1 microM and 1 nM, respectively. The maximum effect of RAs or T3 was not further augmented by the addition of T3 or RAs, respectively. No apparent differences were observed in this study between the actions of RA and 9cRA. The Northern analyses showed that MtT/S cells express retinoic acid receptor alpha2 mRNA and thyroid hormone receptor beta2 mRNA, and DEX did not affect the levels of these mRNAs. This suggests that the role of DEX in enabling RAs or T3 to up-regulate GHRH-R mRNA levels is not an induction of the expression of each specific receptor for RAs and T3. The similar enhancement of DEX induction of GHRH-R mRNA by RAs or T3 was also observed in the fetal rat pituitary gland in culture, suggesting that RA and/or T3 is involved in the mechanisms responsible for the developmentally regulated expression of GHRH-R mRNA.
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Affiliation(s)
- H Nogami
- Department of Anatomy, Keio University School of Medicine, Tokyo, Japan.
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Sherwood NM, Krueckl SL, McRory JE. The origin and function of the pituitary adenylate cyclase-activating polypeptide (PACAP)/glucagon superfamily. Endocr Rev 2000; 21:619-70. [PMID: 11133067 DOI: 10.1210/edrv.21.6.0414] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The pituitary adenylate cyclase-activating polypeptide (PACAP)/ glucagon superfamily includes nine hormones in humans that are related by structure, distribution (especially the brain and gut), function (often by activation of cAMP), and receptors (a subset of seven-transmembrane receptors). The nine hormones include glucagon, glucagon-like peptide-1 (GLP-1), GLP-2, glucose-dependent insulinotropic polypeptide (GIP), GH-releasing hormone (GRF), peptide histidine-methionine (PHM), PACAP, secretin, and vasoactive intestinal polypeptide (VIP). The origin of the ancestral superfamily members is at least as old as the invertebrates; the most ancient and tightly conserved members are PACAP and glucagon. Evidence to date suggests the superfamily began with a gene or exon duplication and then continued to diverge with some gene duplications in vertebrates. The function of PACAP is considered in detail because it is newly (1989) discovered; it is tightly conserved (96% over 700 million years); and it is probably the ancestral molecule. The diverse functions of PACAP include regulation of proliferation, differentiation, and apoptosis in some cell populations. In addition, PACAP regulates metabolism and the cardiovascular, endocrine, and immune systems, although the physiological event(s) that coordinates PACAP responses remains to be identified.
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Affiliation(s)
- N M Sherwood
- Department of Biology, University of Victoria, British Columbia, Canada.
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Halmos G, Schally AV, Varga JL, Plonowski A, Rekasi Z, Czompoly T. Human renal cell carcinoma expresses distinct binding sites for growth hormone-releasing hormone. Proc Natl Acad Sci U S A 2000; 97:10555-60. [PMID: 10962030 PMCID: PMC27063 DOI: 10.1073/pnas.180313097] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/06/2000] [Indexed: 12/28/2022] Open
Abstract
Antagonists of growth hormone-releasing hormone (GHRH) inhibit the proliferation of various human cancers in vitro and in vivo by mechanisms that include apparent direct effects through specific binding sites expressed on tumors and that differ from pituitary human GHRH (hGHRH) receptors. In this study, GHRH antagonist JV-1-38 (20 microgram/day per animal s.c.) inhibited the growth of orthotopic CAKI-1 human renal cell carcinoma (RCC) by 83% and inhibited the development of metastases to lung and lymph nodes. Using ligand competition assays with (125)I-labeled GHRH antagonist JV-1-42, we demonstrated the presence of specific high-affinity (K(d) = 0.25 +/- 0.03 nM) binding sites for GHRH with a maximal binding capacity (B(max)) of 70.2 +/- 4.1 fmol/mg of membrane protein in CAKI-1 tumors. These receptors bind GHRH antagonists preferentially and display a lower affinity for hGHRH. The binding of (125)I-JV-1-42 is not inhibited by vasoactive intestinal peptide (VIP)-related peptides sharing structural homology with hGHRH. The receptors for GHRH antagonists on CAKI-1 tumors are distinct from binding sites detected with (125)I-VIP (K(d) = 0.89 +/- 0.14 nM; B(max) = 183.5 +/- 2.6 fmol/mg of protein) and also have different characteristics from GHRH receptors on rat pituitary as documented by the insignificant binding of [His(1),(125)I-Tyr(10), Nle(27)]hGHRH(1-32)NH(2). Reverse transcription-PCR revealed the expression of splice variants of hGHRH receptor in CAKI-1 RCC. Biodistribution studies demonstrate an in vivo uptake of (125)I-JV-1-42 by the RCC tumor tissue. The presence of specific receptor proteins that bind GHRH antagonists in CAKI-1 RCC supports the view that distinct binding sites that mediate the inhibitory effect of GHRH antagonists are present on various human cancers.
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Affiliation(s)
- G Halmos
- Endocrine, Polypeptide and Cancer Institute, Veterans Affairs Medical Center and Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70112-2699, USA
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Rekasi Z, Czompoly T, Schally AV, Halmos G. Isolation and sequencing of cDNAs for splice variants of growth hormone-releasing hormone receptors from human cancers. Proc Natl Acad Sci U S A 2000; 97:10561-6. [PMID: 10962031 PMCID: PMC27064 DOI: 10.1073/pnas.180313297] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/06/2000] [Indexed: 01/15/2023] Open
Abstract
The proliferation of various tumors is inhibited by the antagonists of growth hormone-releasing hormone (GHRH) in vitro and in vivo, but the receptors mediating the effects of GHRH antagonists have not been identified so far. Using an approach based on PCR, we detected two major splice variants (SVs) of mRNA for human GHRH receptor (GHRH-R) in human cancer cell lines, including LNCaP prostatic, MiaPaCa-2 pancreatic, MDA-MB-468 breast, OV-1063 ovarian, and H-69 small-cell lung carcinomas. In addition, high-affinity, low-capacity binding sites for GHRH antagonists were found on the membranes of cancer cell lines such as MiaPaCa-2 that are negative for the vasoactive intestinal peptide/pituitary adenylate cyclase-activating polypeptide receptor (VPAC-R) or lines such as LNCaP that are positive for VPAC-R. Sequence analysis of cDNAs revealed that the first three exons in SV(1) and SV(2) are replaced by a fragment of retained intron 3 having a new putative in-frame start codon. The rest of the coding region of SV(1) is identical to that of human pituitary GHRH-R, whereas in SV(2) exon 7 is spliced out, resulting in a 1-nt upstream frameshift, which leads to a premature stop codon in exon 8. The intronic sequence may encode a distinct 25-aa fragment of the N-terminal extracellular domain, which could serve as a proposed signal peptide. The continuation of the deduced protein sequence coded by exons 4-13 in SV(1) is identical to that of pituitary GHRH-R. SV(2) may encode a GHRH-R isoform truncated after the second transmembrane domain. Thus SVs of GHRH-Rs have now been identified in human extrapituitary cells. The findings support the view that distinct receptors are expressed on human cancer cells, which may mediate the antiproliferative effect of GHRH antagonists.
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Affiliation(s)
- Z Rekasi
- Endocrine, Polypeptide and Cancer Institute, Veterans Affairs Medical Center, Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70112, USA
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29
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Sugihara H, Emoto N, Tamura H, Kamegai J, Shibasaki T, Minami S, Wakabayashi I. Effect of insulin-like growth factor-I on growth hormone-releasing factor receptor expression in primary rat anterior pituitary cell culture. Neurosci Lett 1999; 276:87-90. [PMID: 10624798 DOI: 10.1016/s0304-3940(99)00801-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We examined the effect of insulin-like growth factor-I (IGF-I) on GH-releasing factor (GRF) receptor expression in the primary rat anterior pituitary cell culture. The levels of GRF receptor mRNA were dose-dependently reduced by IGF-I treatment for 24 h. To clarify whether altered levels of GRF receptor mRNA contribute to GRF receptor concentrations, we examined the GH response to GRF in vitro. There was no difference in basal GH secretion between control and IGF-I pretreated cells, while GRF-stimulated GH secretion in cells pretreated with IGF-I for 24 h was significantly lower than that in control cells. Moreover, specific [125I] Tyr10-human GRF binding to pituitary cells was reduced significantly by IGF-I treatment. These results suggest that IGF-I acts directly on the pituitary and participates in the regulation of GRF receptor expression.
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MESH Headings
- Animals
- Cells, Cultured
- Growth Hormone-Releasing Hormone/drug effects
- Growth Hormone-Releasing Hormone/metabolism
- Insulin-Like Growth Factor I/metabolism
- Insulin-Like Growth Factor I/pharmacology
- Male
- Pituitary Gland, Anterior/drug effects
- Pituitary Gland, Anterior/metabolism
- RNA, Messenger/drug effects
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Receptors, Neuropeptide/drug effects
- Receptors, Neuropeptide/metabolism
- Receptors, Pituitary Hormone-Regulating Hormone/drug effects
- Receptors, Pituitary Hormone-Regulating Hormone/metabolism
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Affiliation(s)
- H Sugihara
- Department of Medicine, Nippon Medical School, Tokyo, Japan.
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Miller TL, Godfrey PA, Dealmeida VI, Mayo KE. The rat growth hormone-releasing hormone receptor gene: structure, regulation, and generation of receptor isoforms with different signaling properties. Endocrinology 1999; 140:4152-65. [PMID: 10465288 DOI: 10.1210/endo.140.9.6977] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The interaction of GHRH with membrane-bound receptors on somatotroph cells of the anterior pituitary is an important step in the regulation of GH synthesis and secretion. The identification of a G protein-coupled receptor for GHRH has made it possible to investigate the pathway by which GHRH regulates pituitary somatotroph cell function. To initiate an analysis of the mechanisms regulating expression and function of the GHRH receptor, the structure of the gene and its promoter region were analyzed. The coding sequence of the rat GHRH receptor gene is contained within 14 exons spanning approximately 15 kb of genomic DNA. Four transcription start sites are located within 286 bp upstream of the initiation codon. The 5' flanking region of the GHRH receptor gene acts as a functional promoter in rat pituitary tumor GH3 cells, and basal promoter activity is enhanced in GH3 and COS7 cells by cotransfection of an expression construct encoding the pituitary-specific transcription factor Pit-1. The rat GHRH receptor gene is subject to at least 1 alternative RNA processing event that generates 2 receptor isoforms differing by 41 amino acids within the third intracellular loop (IL) of the protein. The short isoform of the GHRH receptor is predominant in pituitary cells. The MtT/S pituitary tumor cell line was found to express the GHRH receptor, and different populations of these cells produce predominantly the long or short isoforms of the receptor messenger RNA, suggesting that the alternative splicing can be regulated. Functional analysis of the two GHRH receptor isoforms demonstrates that both bind GHRH, but only the short isoform signals through a cAMP-mediated pathway. Neither receptor isoform is able to stimulate calcium mobilization from internal stores after GHRH treatment. Our findings indicate that the pituitary-specific transcription factor Pit-1 is involved in the somatotroph-specific expression of the GHRH receptor gene and that functionally distinct receptor proteins are generated by an alternative RNA processing mechanism.
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Affiliation(s)
- T L Miller
- Department of Biochemistry, Northwestern University, Evanston, Illinois 60208, USA
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McKay LI, Cidlowski JA. Molecular control of immune/inflammatory responses: interactions between nuclear factor-kappa B and steroid receptor-signaling pathways. Endocr Rev 1999; 20:435-59. [PMID: 10453354 DOI: 10.1210/edrv.20.4.0375] [Citation(s) in RCA: 214] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- L I McKay
- Laboratory of Signal Transduction, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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32
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Ho PK, Fong RS, Kai HS, Lau EH, Ngan ES, Cotton CU, Chow BK. The human secretin receptor gene: genomic organization and promoter characterization. FEBS Lett 1999; 455:209-14. [PMID: 10437774 DOI: 10.1016/s0014-5793(99)00864-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Secretin is the most potent regulator of pancreatic bicarbonate, electrolyte and volume secretion. In this report, the organization of the human secretin receptor (hSR) gene was characterized by overlapping genomic phage clones. The hSR gene consists of 13 exons and 12 introns with all the splice donor and acceptor sites conforming to the canonical GT/AG rule. By transient reporter gene assays, the wild-type promoter, containing 3.0 kb of the hSR gene 5' flanking region, was able to drive 5.8 +/- 0.6 and 6.6 +/- 0.2-fold (P < 0.01) increases in luciferase activities in pancreatic ductule-derived PANC-1 and BPD-1 cells, respectively. By subsequent 5' and 3' deletion analysis, a promoter element was identified within -408 to -158, relative to the ATG codon. This promoter element was found to be cell-specific since it could drive reporter gene expression in PANC-1 and BPD-1 cells but not in Hs 262.St, Hs 746T and alphaT3-1 cells. The study of the transcriptional control of human secretin and its receptor should shed light on the pathological developments of pancreatic cancer and autism in the future.
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Affiliation(s)
- P K Ho
- Department of Zoology, The University of Hong Kong, SAR, PR China
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Nogami H, Inoue K, Moriya H, Ishida A, Kobayashi S, Hisano S, Katayama M, Kawamura K. Regulation of growth hormone-releasing hormone receptor messenger ribonucleic acid expression by glucocorticoids in MtT-S cells and in the pituitary gland of fetal rats. Endocrinology 1999; 140:2763-70. [PMID: 10342867 DOI: 10.1210/endo.140.6.6787] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Regulation of GH-releasing hormone receptor (GHRH-R) messenger RNA (mRNA) expression was studied, with the ribonuclease protection assay, in the fetal rat pituitary gland and in MtT-S clonal cells. GHRH-R mRNA was first detected on embryonic day (E)19 and increased rapidly thereafter, to reach a maximum at E21. Incubation of E17 or E18 pituitaries with 50 nM dexamethasone (DEX), a synthetic glucocorticoid, induced GHRH-R mRNA expression, suggesting that glucocorticoids play a pivotal role in the developmental expression of this mRNA. In E19 pituitaries, 24 h treatment with DEX increased GHRH-R mRNA by 60%, and GH mRNA by 76%, but did not affect pit-1 mRNA level, suggesting that the effect of DEX is specific for expressions of GH mRNA and GHRH-R mRNA. The accumulation of GHRH-R mRNA by DEX was time dependent, and it was slightly enhanced by the protein synthesis inhibitor, puromycin (100 microM). In MtT-S cells (a pituitary cell line established from an estrogen-induced tumor), DEX induced GHRH-R mRNA expression within 2 h in a dose-dependent manner. This induction was augmented by puromycin (100 microM) or cycloheximide (3.5 microM). However, the RNA synthesis inhibitor Actinomycin D (1 microM) completely inhibited GHRH-R mRNA accumulation in response to either DEX or DEX plus puromycin, suggesting that glucocorticoids induce GHRH-R mRNA mainly through stimulation of mRNA transcription. These results suggest: that GHRH-R mRNA accumulation in the fetal pituitary gland of rats normally occurs at E19, probably because of the direct action of glucocorticoids on the pituitary gland, to stimulate GHRH-R mRNA transcription; and that the expression of glucocorticoid receptors is an important event in GH cell development in rats. Accordingly, immunocytochemical results suggest an increase in glucocorticoid receptors in immature GH cells between E17 and E18. The present results also imply that MtT-S cells may be a good model in which to further study the molecular mechanisms of the regulation of GHRH-R gene expression.
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Affiliation(s)
- H Nogami
- Department of Anatomy, School of Medicine, Keio University, Tokyo, Japan
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Iguchi G, Okimura Y, Takahashi T, Mizuno I, Fumoto M, Takahashi Y, Kaji H, Abe H, Chihara K. Cloning and characterization of the 5'-flanking region of the human growth hormone-releasing hormone receptor gene. J Biol Chem 1999; 274:12108-14. [PMID: 10207037 DOI: 10.1074/jbc.274.17.12108] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We cloned the 5'-flanking region of the human growth hormone-releasing hormone receptor (GHRH-R) gene and determined the nucleotide sequence of 2.7 kilobases upstream from the translation start site. RNase protection analysis showed the major transcription start site is 122 base pairs upstream from the translation start site. The 5'-end of the longest product of 5'-rapid amplification of cDNA ends was close to the site. There were no typical TATA homologies but several putative regulatory elements including Pit-1-binding site-like element. Transient transfection studies using a luciferase reporter gene demonstrated that 5'-flanking region had promoter activity in GH3 cells (derived from rat pituitary tumor) but not in nonpituitary cells, BeWo and HeLa cells. However, co-transfection of Pit-1 expression vector increased luciferase activity in BeWo cells. Deletion study showed that the regions from -310 to -130 and from -130 to -120 were important for the GHRH-R gene expression in GH3 cells, although the latter contributed less to the gene expression. In BeWo cells co-transfected with Pit-1 expression vector, the region from -310 to -130 was essential for the Pit-1-dependent expression of GHRH-R gene. The region from -310 to -120 has two putative Pit-1-binding sites, P1 and P2, located from -129 to -123 and from -171 to -160, respectively. Both mobility shift assay and DNase-I footprint analysis showed that P2 had much higher Pit-1 binding affinity than P1. Mutation of P2 decreased GHRH-R gene expression in GH3 cells. These findings were consistent with the results that the region from -310 to -130 is an important element for Pit-1-dependent expression of GHRH-R gene.
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Affiliation(s)
- G Iguchi
- Third Division, Department of Medicine, Kobe University School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
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Petersenn S, Penshorn M, Beil FU, Schulte HM. [Molecular analysis of the human "growth hormone secretagogue"-receptor]. MEDIZINISCHE KLINIK (MUNICH, GERMANY : 1983) 1999; 94:202-6. [PMID: 10373755 DOI: 10.1007/bf03044855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
BACKGROUND Growth hormone secretagogues (GHS) are highly potent synthetic peptides which release growth hormone (GH) by activation of a growth hormone-releasing hormone-independent signal cascade. A specific growth hormone secretagogue receptor (GHS-R) has been isolated, its endogenous ligand is still unknown. It might represent another major endocrine pathway controlling GH secretion. To gain insight into the specific function of the human GHS-R we studied the gene structure. Two variants, type 1a and 1b, have been described, but their specific functions are unknown. METHODS AND RESULTS A specific probe for the GHS-R was cloned following reverse transcription and PCR amplification of pituitary mRNA. A genomic human placenta library was screened for the GHS-R gene. Positive clones were identified and further characterized by Southern blotting and sequencing. A genomic clone of 18 kb in size was determined to include the coding sequence of both GHS-R variants. Here we show that GHS-R type 1a and type 1b are encoded by a single gene. Sequencing of the immediate 5'-flanking region suggests a number of transcription factor binding sites, but their functional significance remains to be investigated. CONCLUSION A genomic clone encoding for the two known variants of the human GHS-R was isolated. Further studies will determine physiological relevance and regulation of GHS-R. This will facilitate studies of GHS as diagnostic and therapeutic agents in GH disorders.
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Affiliation(s)
- S Petersenn
- IHF Institut für Hormon- und Fortpflanzungsforschung, Universität Hamburg.
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Kaji H, Tai S, Okimura Y, Iguchi G, Takahashi Y, Abe H, Chihara K. Cloning and characterization of the 5'-flanking region of the human growth hormone secretagogue receptor gene. J Biol Chem 1998; 273:33885-8. [PMID: 9852035 DOI: 10.1074/jbc.273.51.33885] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Recently, the growth hormone secretagogue receptor (GHS-R) cDNA has been isolated from the pituitary and hypothalamus. To evaluate the regulation of human (h) GHS-R gene expression, we cloned the hGHS-R gene containing the 5'-flanking region of 0.6-2.9 kilobase pairs. Analysis of the hGHS-R transcripts with 5'-rapid amplification of cDNA ends suggested that the putative transcription initiation site was approximately -453 base pairs upstream of the translation initiation site (+1). There is no typical TATA, CAAT, or GC box but an initiator-like sequence and putative binding sites for several transcription factors around the putative transcription start site. The 5'-flanking region inserted into a luciferase reporter vector had promoter activity in GH3 cells but had activity indistinguishable from background in HeLa or EP1 cells. The hGHS-R promoter activity in GH3 cells increased by deletion of nucleotides from -1224 to -734, whereas it was decreased by further deletion from -734 to -608. Knowledge of the promoter region of the hGHS-R gene will facilitate elucidation of its transcriptional control.
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Affiliation(s)
- H Kaji
- Third Division, Department of Medicine, Kobe University School of Medicine, Kobe 650-0017, Japan.
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