1
|
Fortin J, Ongaro L, Li Y, Tran S, Lamba P, Wang Y, Zhou X, Bernard DJ. Minireview: Activin Signaling in Gonadotropes: What Does the FOX say… to the SMAD? Mol Endocrinol 2015; 29:963-77. [PMID: 25942106 DOI: 10.1210/me.2015-1004] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The activins were discovered and named based on their abilities to stimulate FSH secretion and FSHβ (Fshb) subunit expression by pituitary gonadotrope cells. According to subsequent in vitro observations, activins also stimulate the transcription of the GnRH receptor (Gnrhr) and the activin antagonist, follistatin (Fst). Thus, not only do activins stimulate FSH directly, they have the potential to regulate both FSH and LH indirectly by modulating gonadotrope sensitivity to hypothalamic GnRH. Moreover, activins may negatively regulate their own actions by stimulating the production of one of their principal antagonists. Here, we describe our current understanding of the mechanisms through which activins regulate Fshb, Gnrhr, and Fst transcription in vitro. The activin signaling molecules SMAD3 and SMAD4 appear to partner with the winged-helix/forkhead transcription factor, forkhead box L2 (FOXL2), to regulate expression of all 3 genes. However, in vivo data paint a different picture. Although conditional deletion of Foxl2 and/or Smad4 in murine gonadotropes produces impairments in FSH synthesis and secretion as well as in pituitary Fst expression, Gnrhr mRNA levels are either unperturbed or increased in these animals. Surprisingly, gonadotrope-specific deletion of Smad3 alone or with Smad2 does not impair FSH production or fertility; however, mice harboring these mutations may express a DNA binding-deficient, but otherwise functional, SMAD3 protein. Collectively, the available data firmly establish roles for FOXL2 and SMAD4 in Fshb and Fst expression in gonadotrope cells, whereas SMAD3's role requires further investigation. Gnrhr expression, in contrast, appears to be FOXL2, SMAD4, and, perhaps, activin independent in vivo.
Collapse
Affiliation(s)
- Jérôme Fortin
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Luisina Ongaro
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Yining Li
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Stella Tran
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Pankaj Lamba
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Ying Wang
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Xiang Zhou
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| | - Daniel J Bernard
- Department of Pharmacology and Therapeutics (J.F., L.O., Y.L., S.T., P.L., Y.W., X.Z., D.J.B.), McGill University, Montréal, Québec, Canada H3G 1Y6; The Campbell Family Cancer Research Institute (J.F.), Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada M5G 2C1; Diabetes Center (S.T.), Department of Medicine, University of California-San Francisco, San Francisco, California 94143; and Psychiatry (P.L.), St Mary Mercy Hospital, Livonia, Michigan 48154
| |
Collapse
|
2
|
Gajewska A, Herman AP, Wolińska-Witort E, Kochman K, Zwierzchowski L. In vivo oestrogenic modulation of Egr1 and Pitx1 gene expression in female rat pituitary gland. J Mol Endocrinol 2014; 53:355-66. [PMID: 25258388 DOI: 10.1530/jme-14-0092] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
EGR1 and PITX1 are transcription factors required for gonadotroph cell Lhb promoter activation. To determine changes in Egr1 and Pitx1 mRNA levels in central and peripheral pituitary stimulations, an in vivo model based on i.c.v. pulsatile (1 pulse/0.5 h over 2 h) GnRH agonist (1.5 nM buserelin) or antagonist (2 nM antide) microinjections was used. The microinjections were given to ovariectomised and 17β-oestradiol (E2) (3×20 μg), ERA (ESR1) agonist propyl pyrazole triol (PPT) (3×0.5 mg), ERB (ESR2) agonist diarylpropionitrile (DPN) (3×0.5 mg) s.c. pre-treated rats 30 min after last pulse anterior pituitaries were excised. Relative mRNA expression was determined by quantitative RT-PCR (qRT-PCR). Results revealed a gene-specific response for GnRH and/or oestrogenic stimulations in vivo. Buserelin pulses enhanced Egr1 expression by 66% in ovariectomised rats, whereas the oestradiol-supplemented+i.c.v. NaCl-microinjected group showed a 50% increase in Egr1 mRNA expression. The oestrogenic signal was transmitted via ERA (ESR1) and ERB (ESR2) activation as administration of PPT and DPN resulted in 97 and 62%, respectively, elevation in Egr1 mRNA expression. A synergistic action of GnRH agonist and 17β-oestradiol (E2) stimulation of the Egr1 gene transcription in vivo were found. GnRHR activity did not affect Pitx1 mRNA expression; regardless of NaCl, buserelin or antide i.c.v. pulses, s.c. oestrogenic supplementation (with E2, PPT or DPN) consistently decreased (by -46, -48 and -41% respectively) the Pitx1 mRNA in the anterior pituitary gland. Orchestrated Egr1 and Pitx1 activities depending on specific central and peripheral regulatory inputs could be responsible for physiologically variable Lhb gene promoter activation in vivo.
Collapse
Affiliation(s)
- Alina Gajewska
- Department of NeuroendocrinologyThe Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Instytucka Street 3, 05-110 Jablonna n. Warsaw, PolandNeuroendocrinology DepartmentMedical Centre for Postgraduate Education, Marymoncka 99/103 Street, 01-813 Warsaw, PolandDepartment of Molecular BiologyInstitute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, 05-552 Magdalenka, Poland
| | - Andrzej P Herman
- Department of NeuroendocrinologyThe Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Instytucka Street 3, 05-110 Jablonna n. Warsaw, PolandNeuroendocrinology DepartmentMedical Centre for Postgraduate Education, Marymoncka 99/103 Street, 01-813 Warsaw, PolandDepartment of Molecular BiologyInstitute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, 05-552 Magdalenka, Poland
| | - Ewa Wolińska-Witort
- Department of NeuroendocrinologyThe Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Instytucka Street 3, 05-110 Jablonna n. Warsaw, PolandNeuroendocrinology DepartmentMedical Centre for Postgraduate Education, Marymoncka 99/103 Street, 01-813 Warsaw, PolandDepartment of Molecular BiologyInstitute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, 05-552 Magdalenka, Poland
| | - Kazimierz Kochman
- Department of NeuroendocrinologyThe Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Instytucka Street 3, 05-110 Jablonna n. Warsaw, PolandNeuroendocrinology DepartmentMedical Centre for Postgraduate Education, Marymoncka 99/103 Street, 01-813 Warsaw, PolandDepartment of Molecular BiologyInstitute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, 05-552 Magdalenka, Poland
| | - Lech Zwierzchowski
- Department of NeuroendocrinologyThe Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Instytucka Street 3, 05-110 Jablonna n. Warsaw, PolandNeuroendocrinology DepartmentMedical Centre for Postgraduate Education, Marymoncka 99/103 Street, 01-813 Warsaw, PolandDepartment of Molecular BiologyInstitute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, 05-552 Magdalenka, Poland
| |
Collapse
|
3
|
Fortin J, Boehm U, Deng CX, Treier M, Bernard DJ. Follicle-stimulating hormone synthesis and fertility depend on SMAD4 and FOXL2. FASEB J 2014; 28:3396-410. [PMID: 24739304 DOI: 10.1096/fj.14-249532] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Follicle-stimulating hormone (FSH) is an essential regulator of gonadal function and fertility. Loss-of-function mutations in the FSHB/Fshb gene cause hypogonadotropic hypogonadism in humans and mice. Both gonadotropin-releasing hormone (GnRH) and activins, members of the transforming growth factor β (TGFβ) superfamily, stimulate FSH synthesis; yet, their relative roles and mechanisms of action in vivo are unknown. Here, using conditional gene-targeting, we show that the canonical mediator of TGFβ superfamily signaling, SMAD4, is absolutely required for normal FSH synthesis in both male and female mice. Moreover, when the Smad4 gene is ablated in combination with its DNA binding cofactor Foxl2 in gonadotrope cells, mice make essentially no FSH and females are sterile. Indeed, the phenotype of these animals is remarkably similar to that of Fshb-knockout mice. Not only do these results establish SMAD4 and FOXL2 as essential master regulators of Fshb transcription in vivo, they also suggest that activins, or related ligands, could play more important roles in FSH synthesis than GnRH.
Collapse
Affiliation(s)
- Jérôme Fortin
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada;
| | - Ulrich Boehm
- Department of Pharmacology and Toxicology, University of Saarland School of Medicine, Homburg, Germany
| | - Chu-Xia Deng
- National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, USA; and
| | - Mathias Treier
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Daniel J Bernard
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada;
| |
Collapse
|
4
|
Skarra DV, Arriola DJ, Benson CA, Thackray VG. Forkhead box O1 is a repressor of basal and GnRH-induced Fshb transcription in gonadotropes. Mol Endocrinol 2013; 27:1825-39. [PMID: 24065703 DOI: 10.1210/me.2013-1185] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Synthesis of the gonadotropin β-subunits is tightly controlled by a complex network of hormonal signaling pathways that may be modulated by metabolic cues. Recently, we reported that insulin regulates FOXO1 phosphorylation and cellular localization in pituitary gonadotropes and that FOXO1 overexpression inhibits Lhb transcription. In the current study, we investigated whether FOXO1 modulates Fshb synthesis. Here, we demonstrate that FOXO1 represses basal and GnRH-induced Fshb transcription in LβT2 cells. In addition, we show that PI3K inhibition, which increases FOXO1 nuclear localization, results in decreased Fshb mRNA levels in murine primary pituitary cells. FOXO1 also decreases transcription from the human FSHB promoter, suggesting that FOXO1 regulation of FSHB transcription may be conserved between rodents and humans. Although the FOXO1 DNA-binding domain is necessary for suppression of Fshb, we do not observe direct binding of FOXO1 to the Fshb promoter, suggesting that FOXO1 exerts its effect through protein-protein interactions with transcription factors required for Fshb synthesis. FOXO1 suppression of basal Fshb transcription may involve PITX1 because PITX1 interacts with FOXO1, FOXO1 repression maps to the proximal Fshb promoter containing a PITX1-binding site, PITX1 induction of Fshb or a PITX1 binding element in CV-1 cells is decreased by FOXO1, and FOXO1 suppresses Pitx1 mRNA and protein levels. GnRH induction of an Fshb promoter containing a deletion at -50/-41 or -30/-21 is not repressed by FOXO1, suggesting that these two regions may be involved in FOXO1 suppression of GnRH-induced Fshb synthesis. In summary, our data demonstrate that FOXO1 can negatively regulate Fshb transcription and suggest that FOXO1 may relay metabolic hormonal signals to modulate gonadotropin production.
Collapse
Affiliation(s)
- Danalea V Skarra
- PhD, Department of Reproductive Medicine, University of California, San Diego, 9500 Gilman Drive, MC 0674, La Jolla, CA 92093.
| | | | | | | |
Collapse
|
5
|
Jia J, Shafiee-Kermani F, Miller WL. Gonadotrope-specific expression and regulation of ovine follicle stimulating hormone Beta: transgenic and adenoviral approaches using primary murine gonadotropes. PLoS One 2013; 8:e66852. [PMID: 23874399 PMCID: PMC3715487 DOI: 10.1371/journal.pone.0066852] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 05/13/2013] [Indexed: 01/21/2023] Open
Abstract
The beta subunit of follicle stimulating hormone (FSHB) is expressed specifically in pituitary gonadotropes in vertebrates. Transgenic mouse studies have shown that enhancers in the proximal promoter between −172/−1 bp of the ovine FSHB gene are required for gonadotrope expression of ovine FSHB. These enhancers are associated with regulation by activins and gonadotropin releasing hormone (GnRH). Additional distal promoter sequence between −4741/−750 bp is also required for expression. New transgenic studies presented here focus on this distal region and narrow it to 1116 bp between −1866/−750 bp. In addition, adenoviral constructs were produced to identify these critical distal sequences using purified primary mouse gonadotropes as an in vitro model system. The adenoviral constructs contained −2871 bp, −750 bp or −232 bp of the ovine FSHB promoter. They all showed gonadotrope-specific regulation since they were induced only in purified primary gonadotropes by activin A (50 ng/ml) and inhibited by GnRH (100 nM) in the presence of activin (except −232FSHBLuc). However, basal expression of all three viral constructs (in the presence of follistatin to block cellular induction by activin) was relatively high in pituitary non-gonadotropes as well as gonadotropes. Thus, gonadotrope-specific regulation associated with the proximal promoter was observed as expected, but the model was blind to distal promoter elements between −2871/−750 necessary for gonadotrope-specific expression of ovine FSHB in vivo. The new adenoviral-based in vitro technique did detect, however, a novel GnRH response element between −750 bp and −232 bp of the ovine FSHB promoter. We conclude that adenoviral-based studies in primary gonadotropes can adequately recognize regulatory elements on the ovine FSHB promoter associated with gonadotrope-specific regulation/expression, but that more physiologically based techniques, such as transgenic studies, will be needed to identify sequences between −1866/−750 bp of the ovine FSHB promoter that are also required for tissue/cell specific expression in vivo.
Collapse
Affiliation(s)
- Jingjing Jia
- Mount Sinai School of Medicine, Department of Neurology, New York City, New York, United States of America
| | - Farideh Shafiee-Kermani
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina, United States of America
| | - William L. Miller
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina, United States of America
- * E-mail:
| |
Collapse
|
6
|
Bernard DJ, Tran S. Mechanisms of activin-stimulated FSH synthesis: the story of a pig and a FOX. Biol Reprod 2013; 88:78. [PMID: 23426431 DOI: 10.1095/biolreprod.113.107797] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Activins were discovered and, in fact, named more than a quarter century ago based on their abilities to stimulate pituitary follicle-stimulating hormone (FSH) synthesis and secretion. However, it is only in the last decade that we have finally come to understand their underlying mechanisms of action in gonadotroph cells. In this minireview, we chronicle the research that led to the recent discovery of forkhead box L2 (FOXL2) as an essential mediator of activin-regulated FSH beta subunit (Fshb) transcription in vitro and in vivo.
Collapse
Affiliation(s)
- Daniel J Bernard
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada.
| | | |
Collapse
|
7
|
Thompson IR, Ciccone NA, Xu S, Zaytseva S, Carroll RS, Kaiser UB. GnRH pulse frequency-dependent stimulation of FSHβ transcription is mediated via activation of PKA and CREB. Mol Endocrinol 2013; 27:606-18. [PMID: 23393127 DOI: 10.1210/me.2012-1281] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Expression of pituitary FSH and LH, under the control of pulsatile GnRH, is essential for fertility. cAMP response element-binding protein (CREB) has been implicated in the regulation of FSHβ gene expression, but the molecular mechanisms by which pulsatile GnRH regulates CREB activation remain poorly understood. We hypothesized that CREB is activated by a distinct signaling pathway in response to pulsatile GnRH in a frequency-dependent manner to dictate the FSHβ transcriptional response. GnRH stimulation of CREB phosphorylation (pCREB) in the gonadotrope-derived LβT2 cell line was attenuated by a protein kinase A (PKA) inhibitor, H89. A dominant negative PKA (DNPKA) reduced GnRH-stimulated pCREB and markedly decreased GnRH stimulation of FSHβ mRNA and FSHβLUC activity, but had little effect on LHβLUC activity, indicating relative specificity of this pathway. In perifusion studies, FSHβ mRNA levels and FSHβLUC activities were increased by pulsatile GnRH, with significantly greater increases at low compared with high pulse frequencies. DNPKA markedly reduced these GnRH-stimulated FSHβ responses at both low and high pulse frequencies. Correlating with FSHβ activation, both PKA activity and levels of pCREB were increased to a greater extent by low compared with high GnRH pulse frequencies, and the induction of pCREB was also attenuated by overexpression of DNPKA at both low and high pulse frequencies. Taken together, these data indicate that a PKA-mediated signaling pathway mediates GnRH activation of CREB at low-pulse frequencies, playing a significant role in the decoding of the hypothalamic GnRH signal to result in frequency-dependent FSHβ activation.
Collapse
Affiliation(s)
- Iain R Thompson
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | | | | | | | | | | |
Collapse
|
8
|
Kato T, Ishikawa A, Yoshida S, Sano Y, Kitahara K, Nakayama M, Susa T, Kato Y. Molecular cloning of LIM homeodomain transcription factor Lhx2 as a transcription factor of porcine follicle-stimulating hormone beta subunit (FSHβ) gene. J Reprod Dev 2011; 58:147-55. [PMID: 22134063 DOI: 10.1262/jrd.11-099s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We cloned the LIM-homeodomain protein LHX2 as a transcription factor for the porcine follicle-stimulating hormone β subunit gene (Fshβ) by the Yeast One-Hybrid Cloning System using the upstream region of -852/-746 bases (b) from the transcription start site, called Fd2, as a bait sequence. The reporter assay in LβT2 and CHO cells revealed the presence of an LHX2-responsive region other than Fd2. A potential LHX2 binding sequence was confirmed as AATTAAT containing a consensus homeodomain binding core sequence AATT by Systematic Evolution of Ligands by Exponential Enrichment analysis. DNase I footprinting demonstrated three AATTAAT sequences located at regions -835/-829, -818/-812 and -806/-800 b in the Fd2 region and 12 binding sites in the distal and proximal regions mostly containing an AATT-core sequence. RT-PCR analysis of Lhx2 expression during porcine fetal and postnatal pituitary development showed a gradual increase from fetal day (f) 40 to postnatal day (p) 8 followed by a slight decrease to p230, suggesting that LHX2 may play its role largely in the late fetal and postnatal periods. The analyses of Lhx2 expression in pituitary tumor-derived cell lines showed their expressions in cell lines including αT31, LβT2 and others. Since LHX2 was previously identified as a transcription factor for Cga and the in vitro experiments in the present study suggested that LHX2 regulated the expression of Fshβ, it is possible that LHX2 controls the synthesis of FSH at the transcription level.
Collapse
Affiliation(s)
- Takako Kato
- Institute of Reproduction and Endocrinology, Meiji University, Kanagawa 214-8571, Japan
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Lo A, Zheng W, Gong Y, Crochet JR, Halvorson LM. GATA transcription factors regulate LHβ gene expression. J Mol Endocrinol 2011; 47:45-58. [PMID: 21571865 DOI: 10.1530/jme-10-0137] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The GATA family of transcription factors are critical determinants of cell differentiation as well as regulation of adult gene expression throughout the reproductive axis. Within the anterior pituitary gland, GATA factors have been shown to increase glycoprotein α-subunit gene promoter activity; however, nothing has been known about the impact of these factors on expression of the gonadotropin β-subunits. In this study, we demonstrate expression of both GATA2 and GATA4 in primary mouse gonadotropes and the gonadotrope cell line, LβT2. Based on the transient transfection in fibroblast cells, GATA factors increase LH β-subunit gene (LHβ) promoter activity alone and in synergy with the orphan nuclear receptors steroidogenic factor-1 (SF-1) and liver receptor homologue-1 (LRH-1). The GATA response was localized to a DNA regulatory region at position -101 in the rat LHβ gene promoter which overlaps with a previously described cis-element for pituitary homeobox-1 (Pitx1) and is flanked by two SF-1/LRH-1 regulatory sites. As determined by gel shift, GATA and Pitx1 can compete for binding to this element. Furthermore, mutation analysis revealed a requirement for both the GATA/Pitx1 and the SF-1/LRH-1 cis-elements in order to achieve synergy. These studies identify a novel role for GATA transcription factors in the pituitary and reveal additional molecular mechanisms by which precise modulation of LHβ gene expression can be achieved.
Collapse
Affiliation(s)
- Ann Lo
- Division of Reproductive Endocrinology, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9032, USA
| | | | | | | | | |
Collapse
|
10
|
Justice NJ, Blount AL, Pelosi E, Schlessinger D, Vale W, Bilezikjian LM. Impaired FSHbeta expression in the pituitaries of Foxl2 mutant animals. Mol Endocrinol 2011; 25:1404-15. [PMID: 21700720 DOI: 10.1210/me.2011-0093] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Forkhead box L2 (FoxL2) is required for ovarian development and differentiation. FoxL2 is also expressed in the pituitary where it has been implicated in the development and regulation of gonadotropes, which secrete LH and FSH, the endocrine signals that regulate folliculogenesis in the ovary and spermatogenesis in the testis. Here, we show that FoxL2 is not required for the specification of gonadotropes; the pituitaries of Foxl2 mutant mice contain normal numbers of gonadotropes that express glycoprotein α subunit and LHβ. Whereas the specification of gonadotropes and all other hormonal cell types is normal in the pituitaries of Foxl2 mutant animals, FSHβ levels are severely impaired in both male and female animals, suggesting that FoxL2 is required for normal Fshb expression. The size of the pituitary is reduced in proportion to the smaller body size of Foxl2 mutants, with a concomitant increase in the pituitary cellular density. In primary pituitary cultures, activin induces FSH secretion and Fshb mRNA expression in cells from wild-type mice. In cells from Foxl2 mutant mice, however, FSH secretion is not detected, and activin is unable to drive Fshb expression, suggesting that the mechanism of activin-dependent activation of Fshb transcription is impaired. However, a small number of gonadotropes in the ventromedial region of the pituitaries from Foxl2 mutant mice maintain FSHβ expression, suggesting that a FoxL2- and activin-independent mechanism can drive Fshb transcription. These data indicate that, in addition to its role in the ovary, FoxL2 function in the pituitary is required for normal expression of FSH.
Collapse
Affiliation(s)
- Nicholas J Justice
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | | | | | | | | | | |
Collapse
|
11
|
Coss D, Mellon PL, Thackray VG. A FoxL in the Smad house: activin regulation of FSH. Trends Endocrinol Metab 2010; 21:562-8. [PMID: 20598900 PMCID: PMC2933269 DOI: 10.1016/j.tem.2010.05.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 05/26/2010] [Accepted: 05/27/2010] [Indexed: 10/19/2022]
Abstract
Follicle-stimulating hormone (FSH), produced by pituitary gonadotrope cells, is required for maturation of ovarian follicles. The FSHbeta subunit is the limiting factor for production of mature hormone and provides biological specificity. Activin dramatically induces FSHbeta transcription and the secondary rise in FSH, important for follicular development, is dependent on this induction. Thus, regulation of FSHbeta levels by activin is crucial for female reproductive fitness. This review discusses activin signaling pathways, transcription factors and FSHbeta promoter elements required for activin responsiveness. Because FoxL2, a forkhead transcription factor, was recently shown to be instrumental in relaying activin signaling to the FSHbeta promoter, we focus in this paper on its role and the inter-relatedness of several key players in activin responsiveness on the FSHbeta promoter.
Collapse
|
12
|
Bernard DJ, Fortin J, Wang Y, Lamba P. Mechanisms of FSH synthesis: what we know, what we don't, and why you should care. Fertil Steril 2010; 93:2465-85. [DOI: 10.1016/j.fertnstert.2010.03.034] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Accepted: 03/11/2010] [Indexed: 12/17/2022]
|
13
|
Corpuz PS, Lindaman LL, Mellon PL, Coss D. FoxL2 Is required for activin induction of the mouse and human follicle-stimulating hormone beta-subunit genes. Mol Endocrinol 2010; 24:1037-51. [PMID: 20233786 DOI: 10.1210/me.2009-0425] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Activin is a major physiological regulator of FSH. We identify FoxL2 as a critical component in activin induction of FSHbeta, both for the mouse gene, induction of which is Sma- and Mad-related protein (Smad) dependent, and for the human gene that is Smad independent. FoxL2 has been shown to regulate gonadotrope gene expression (GnRH receptor, alpha-glycoprotein subunit, porcine FSHbeta, and follistatin), but the mechanisms of action are not well understood. We identify novel sites required for activin action in both the mouse and human FSHbeta promoters, some of which bind FoxL2, and show that the FoxL2-binding element encompasses a larger region (12 bp) than the previously identified forkhead-binding consensus (7 bp). Remarkably, although required for activin induction, FoxL2 sites neither contribute to basal FSHbeta promoter activity nor confer activin response to a heterologous promoter; thus, they are neither classical activin-response elements nor is their role solely to recruit Smads to the promoter. FoxL2 overexpression can potentiate activin induction in gonadotropes and can confer activin responsiveness to FSHbeta in heterologous cells where this promoter is normally refractory to activin induction. Although Smad3 requires the presence of FoxL2 sites to induce mouse FSHbeta, even through its consensus Smad-binding element; the human promoter, which is induced by activin independently of Smad3, also requires FoxL2 sites for its induction by activin; thus the actions of FoxL2 are not exclusively through interactions with the Smad pathway. Thus, FoxL2 plays a key role in activin induction of the FSHbeta gene, by binding to sites conserved across multiple species.
Collapse
Affiliation(s)
- Patrick S Corpuz
- Department of Reproductive Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0674, USA
| | | | | | | |
Collapse
|
14
|
Luo Z, Wijeweera A, Oh Y, Liou YC, Melamed P. Pin1 facilitates the phosphorylation-dependent ubiquitination of SF-1 to regulate gonadotropin beta-subunit gene transcription. Mol Cell Biol 2010; 30:745-63. [PMID: 19995909 PMCID: PMC2812243 DOI: 10.1128/mcb.00807-09] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 09/10/2009] [Accepted: 11/23/2009] [Indexed: 11/20/2022] Open
Abstract
Pin1 is a peptidyl-prolyl cis-trans isomerase which catalyzes the isomerization of phosphorylated Ser/Thr-Pro peptide bonds. Pin1 knockout mice have marked abnormalities in their reproductive development and function. However, the molecular mechanisms underlying their reproductive defects are poorly understood. Herein, we demonstrate that Pin1 is required for both basal and GnRH-induced gonadotropin beta-subunit gene transcription, through interactions with the transcription factors SF-1, Pitx1, and Egr-1. Pin1 activates transcription of the gonadotropin beta-subunit genes synergistically with these transcription factors, either by modulating their stability or by increasing their protein-protein interactions. Notably, we provide evidence that Pin1 is required for the Ser203 phosphorylation-dependent ubiquitination of SF-1, which facilitates SF-1-Pitx1 interactions and therefore results in an enhancement of SF-1 transcriptional activity. Furthermore, we demonstrate that in gonadotrope cells, sufficient levels of activated Pin1 are maintained through transcriptional and posttranslational regulation by GnRH-induced signaling cascades. Our results suggest that Pin1 functions as a novel player in GnRH-induced signal pathways and is involved in gonadotropin beta-subunit gene transcription by modulating the activity of various specific transcription factors.
Collapse
Affiliation(s)
- Zhuojuan Luo
- Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, Singapore 117543, Singapore, Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Andrea Wijeweera
- Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, Singapore 117543, Singapore, Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Yingzi Oh
- Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, Singapore 117543, Singapore, Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Yih-Cherng Liou
- Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, Singapore 117543, Singapore, Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Philippa Melamed
- Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, Singapore 117543, Singapore, Faculty of Biology, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| |
Collapse
|
15
|
Melamed P. Hormonal signaling to follicle stimulating hormone beta-subunit gene expression. Mol Cell Endocrinol 2010; 314:204-12. [PMID: 19481581 DOI: 10.1016/j.mce.2009.05.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2009] [Revised: 05/20/2009] [Accepted: 05/21/2009] [Indexed: 11/27/2022]
Abstract
Expression of the hormone-specific beta-subunit of follicle stimulating hormone (FSHbeta) is regulated primarily by gonadotropin releasing hormone (GnRH) and activin, with additional feedback by various steroids. While the nature of this hormonal regulation appears conserved, the molecular mechanisms mediating these effects appear less so. This is apparent from the diverse cis-elements required for hormonal stimulation in different species, distinct transcription factors that seem to mediate the effects, as well as the lack of conservation of several reportedly functional cis-elements across species. Recent additional information on the molecular mechanisms through which these regulatory hormones exert their effects, supports the possibility of species-specific mechanisms of regulation, while some redundancy may exist in signaling by the activated transcription factors which allows preservation of the hormonal regulation in these different promoter contexts.
Collapse
Affiliation(s)
- Philippa Melamed
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel.
| |
Collapse
|
16
|
Frequency-dependent regulation of follicle-stimulating hormone beta by pulsatile gonadotropin-releasing hormone is mediated by functional antagonism of bZIP transcription factors. Mol Cell Biol 2009; 30:1028-40. [PMID: 20008557 DOI: 10.1128/mcb.00848-09] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Oscillatory synthesis and secretion of the gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), under the control of pulsatile hypothalamic gonadotropin-releasing hormone (GnRH), is essential for normal reproductive development and fertility. The molecular mechanisms by which various patterns of pulsatile GnRH regulate gonadotrope responsiveness remain poorly understood. In contrast to the alpha and LH beta subunit genes, FSH beta subunit transcription is preferentially stimulated at low rather than high frequencies of pulsatile GnRH. In this study, mutation of a cyclic AMP response element (CRE) within the FSH beta promoter resulted in the loss of preferential GnRH stimulation at low pulse frequencies. We hypothesized that high GnRH pulse frequencies might stimulate a transcriptional repressor(s) to attenuate the action of CRE binding protein (CREB) and show that inducible cAMP early repressor (ICER) fulfills such a role. ICER was not detected under basal conditions, but pulsatile GnRH stimulated ICER to a greater extent at high than at low pulse frequencies. ICER binds to the FSH beta CRE site to reduce CREB occupation and abrogates both maximal GnRH stimulation and GnRH pulse frequency-dependent effects on FSH beta transcription. These data suggest that ICER production antagonizes the stimulatory action of CREB to attenuate FSH beta transcription at high GnRH pulse frequencies, thereby playing a critical role in regulating cyclic reproductive function.
Collapse
|
17
|
Han SO, Miller WL. Activin A induces ovine follicle stimulating hormone beta using -169/-58 bp of its promoter and a simple TATA box. Reprod Biol Endocrinol 2009; 7:66. [PMID: 19552818 PMCID: PMC2714312 DOI: 10.1186/1477-7827-7-66] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Accepted: 06/24/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Activin A increases production of follicle stimulating hormone (FSH) by inducing transcription of its beta subunit (FSHB). This induction has been studied here in LbetaT2 gonadotropes using transient expression of ovine FSHBLuc (-4741 bp of ovine FSHB promoter plus exon/intron 1 linked to Luc). Several sequences between -169/-58 bp of the ovine FSHB proximal promoter are necessary for induction by activin A in LbetaT2 cells, but deletions between -4741/-752 bp decrease induction > 70% suggesting the existence of other important 5' sequences. Induction disappears if a minimal T81 thymidine kinase promoter replaces the ovine FSHB TATA box and 3' exon/intron. The study reported here was designed to determine if sequences outside -169/-58 bp are important for induction of ovine FSHB by activin A. METHODS Progressively longer deletions of ovine FSHBLuc were created between -4741/-195 bp. Deletions internal to this region were created also, but replaced with substitute DNA. The ovine FSHB TATA box region (-40/+3 bp) was replaced by thymidine kinase and rat prolactin minimal promoters, and substitutions were made in 3' intron/exon sequences. All constructs were tested for basal and activin A-induced expression in LbetaT2 cells. RESULTS Successive 5' deletions progressively lowered fold-induction by activin A from 9.5 to zero, but progressively increased basal expression. Replacing deletions with substitute DNA showed no changes in basal expression or fold-induction. Induction by activin A was supported by the minimal rat prolactin promoter (TATA box) but not the thymidine kinase promoter (no TATA box). Replacement mutations in the 3' region did not decrease induction by activin A. CONCLUSION The data show that specific ovine FSHB sequences 5' to -175 bp or 3' of the transcription start site are not required for induction by activin A. A minimal TATA box promoter supports induction by activin A, but the sequence between the TATA box and transcription start site seems unimportant.
Collapse
Affiliation(s)
- Sang-oh Han
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina, 27695-7622, USA
| | - William L Miller
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina, 27695-7622, USA
| |
Collapse
|
18
|
Susa T, Ishikawa A, Kato T, Nakayama M, Kato Y. Molecular cloning of paired related homeobox 2 (prx2) as a novel pituitary transcription factor. J Reprod Dev 2009; 55:502-11. [PMID: 19550106 DOI: 10.1262/jrd.20256] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study aimed to identify protein(s) that bind(s) to the highly AT-rich sequence of porcine Fshb promoter region -852/-746 (named Fd2) by the Yeast One-Hybrid Cloning System and finally a paired related homeodomain transcription factor, Prx2, known as a key factor for skeletogenesis was cloned. RT-PCR analysis of fetal and postnatal porcine pituitaries demonstrated that Prx2 starts to be expressed at around fetal days 40-50 just before the beginning of Lhb-expression and that the level of Prx2 increases after birth. Immunohistochemical analysis of the prepubertal porcine pituitary revealed that some Prx2-positive cells overlap some Lh beta-positive cells. Transient transfection assay using non-pituitary CHO cells and pituitary tumor-derived LbetaT2 cells revealed that Prx2 plays a cell-type dependent role in modulation of the Fshb promoter, showing stimulation in CHO cells and repression in LbetaT2 cells via the regions of Fd2 and -596/-239. The binding ability of Prx2 to the regions of Fd2 and -596/-239 was confirmed by electrophoretic mobility shift assay. DNase I footprinting revealed that broad regions of Fd2 were bound by Prx2 and that -596/-239 contained seven Prx2-binding sites. The SELEX method using a random N15-mer oligonucleotide pool demonstrated that Prx2 monomer binds to a TAATT motif, which is present in Fd2 and -596/-239. However, the binding of Prx2 to TAATT with a single molecule and its inverted repeat with two molecules could not induce transcriptional activation, indicating that the Prx2-dependent transcriptional modulation demonstrated in cultured cells is not introduced by Prx2 alone. Thus, this study demonstrated for the first time that Prx2 is expressed in the pituitary gland and at least in a part of gonadotropes in which Prx2 may play a role in repression of the Fshb gene.
Collapse
Affiliation(s)
- Takao Susa
- Division of Life Science, Graduate School of Agriculture, Meiji University, Kanagawa, Japan
| | | | | | | | | |
Collapse
|
19
|
Ishikawa A, Kato T, Susa T, Sano A, Kato Y. Molecular cloning and characterization of porcine homeodomain transcription factor Msx1. J Reprod Dev 2009; 55:278-82. [PMID: 19262020 DOI: 10.1262/jrd.20179] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We cloned a porcine ortholog of homeodomain transcription factor Msx1 from the porcine pituitary cDNA library. The amino acid sequence of Msx1 shows high conservation among mammalian species. RT-PCR for porcine fetal and postnatal pituitaries showed that Msx1 is already expressed at early fetal day 40, decreases to a low level before birth and then remarkably decreases after birth. On the other hand, Msx1 expression was observed in all pituitary-derived cell line tested, with most in a gonadotrope lineage LbetaT4. Transfection assay demonstrated that Msx1 markedly repressed the basal Cga and Fshb gene expression, while Lhb expression was affected slightly. Taken together, Msx1 may play a role in repressing gene expression in the fetal and postnatal periods.
Collapse
Affiliation(s)
- Akio Ishikawa
- Division of Life Science, Graduate School of Agriculture, Meiji University
| | | | | | | | | |
Collapse
|
20
|
Wang S, Zhu Y, Melamed P. The molecular regulation of Chinook salmon gonadotropin beta-subunit gene transcription. Gen Comp Endocrinol 2009; 161:34-41. [PMID: 18789942 DOI: 10.1016/j.ygcen.2008.08.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Accepted: 08/22/2008] [Indexed: 11/25/2022]
Abstract
Expression of the gonadotropin beta-subunit genes is tightly regulated both cell-specifically and by the regulatory hormones to achieve the appropriate gonadotropic hormone levels required for reproductive development and function. Although the cDNA sequences of these genes are highly conserved across species, their promoter sequences are not and few functional studies have been carried out to understand the molecular mechanisms through which their expression is regulated. We and others have carried out several studies on the LHbeta gene promoter of Chinook salmon (Oncorhynchus tschawytscha), and also isolated the FSHbeta gene from the same species. We present here a review of these studies and also novel data pertaining to both genes, in an attempt to collate the current understanding of the molecular regulation of the gonadotropin beta-subunit genes in these fish.
Collapse
Affiliation(s)
- Sihui Wang
- Department of Biological Sciences, National University of Singapore, Singapore
| | | | | |
Collapse
|
21
|
Ciccone NA, Lacza CT, Hou MY, Gregory SJ, Kam KY, Xu S, Kaiser UB. A composite element that binds basic helix loop helix and basic leucine zipper transcription factors is important for gonadotropin-releasing hormone regulation of the follicle-stimulating hormone beta gene. Mol Endocrinol 2008; 22:1908-23. [PMID: 18550775 DOI: 10.1210/me.2007-0455] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Although FSH plays an essential role in controlling gametogenesis, the biology of FSHbeta transcription remains poorly understood, but is known to involve the complex interplay of multiple endocrine factors including GnRH. We have identified a GnRH-responsive element within the rat FSHbeta promoter containing an E-box and partial cAMP response element site that are bound by the basic helix loop helix transcription factor family members, upstream stimulating factor (USF)-1/USF-2, and the basic leucine zipper member, cAMP response element-binding protein (CREB), respectively. Expression studies with CREB, USF-1/USF-2, and activating protein-1 demonstrated that the USF transcription factors increased basal transcription, an effect not observed if the cognate binding site was mutated. Conversely, expression of a dominant negative CREB mutant or CREB knockdown attenuated induction by GnRH, whereas dominant negative Fos or USF had no effect on the GnRH response. GnRH stimulation specifically induced an increase in phosphorylated CREB occupation of the FSHbeta promoter, leading to the recruitment of CREB-binding protein to enhance gene transcription. In conclusion, a composite element bound by both USF and CREB serves to integrate signals for basal and GnRH-stimulated transcription of the rat FSHbeta gene.
Collapse
Affiliation(s)
- Nick A Ciccone
- Brigham and Women's Hospital, Division of Endocrinology, Diabetes and Hypertension, 221 Longwood Avenue, Boston, Massachusetts 0211, USA
| | | | | | | | | | | | | |
Collapse
|
22
|
Lamba P, Khivansara V, D'Alessio AC, Santos MM, Bernard DJ. Paired-like homeodomain transcription factors 1 and 2 regulate follicle-stimulating hormone beta-subunit transcription through a conserved cis-element. Endocrinology 2008; 149:3095-108. [PMID: 18339718 PMCID: PMC2408822 DOI: 10.1210/en.2007-0425] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Accepted: 03/03/2008] [Indexed: 11/19/2022]
Abstract
Paired-like homeodomain transcription factors (PITX) regulate the activity of pituitary hormone-encoding genes. Here, we examined mechanisms through which the family of PITX proteins control murine FSH beta-subunit (Fshb) transcription. We observed that endogenous PITX1 and PITX2 isoforms from murine LbetaT2 gonadotrope cells could bind a highly conserved proximal cis-element. Transfection of PITX1 or PITX2C in heterologous cells stimulated both murine and human Fshb/FSHB promoter-reporter activities, and in both cases, mutation of the critical cis-element abrogated these effects. In homologous LbetaT2 cells, the same mutation decreased basal reporter activity and greatly reduced activin A-stimulated transcription from murine and human promoter-reporters. Transfecting dominant-negative forms of PITX1 or PITX2C or knocking down PITX1 or -2 expression by RNA interference in LbetaT2 cells inhibited murine Fshb transcription, confirming roles for endogenous PITX proteins. Both PITX1 and PITX2C interacted with Smad3 (an effector of the activin signaling cascade in these cells) in coprecipitation experiments, and the PITX binding site mutation greatly inhibited Smad2/3/4-stimulated Fshb transcription. In summary, both PITX1 and PITX2C regulate murine and human Fshb/FSHB transcription through a conserved cis-element in the proximal promoter. Furthermore, the data indicate both common and distinct mechanisms of PITX1 and PITX2C action.
Collapse
Affiliation(s)
- Pankaj Lamba
- Department of Pharmacology and Therapeutics, McGill University, McIntyre Medical Sciences Building, Montreal, Quebec, Canada H3G 1Y6
| | | | | | | | | |
Collapse
|
23
|
Blount AL, Vaughan JM, Vale WW, Bilezikjian LM. A Smad-binding Element in Intron 1 Participates in Activin-dependent Regulation of the Follistatin Gene. J Biol Chem 2008; 283:7016-26. [DOI: 10.1074/jbc.m709502200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
|
24
|
Zhu X, Gleiberman AS, Rosenfeld MG. Molecular physiology of pituitary development: signaling and transcriptional networks. Physiol Rev 2007; 87:933-63. [PMID: 17615393 DOI: 10.1152/physrev.00006.2006] [Citation(s) in RCA: 237] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The pituitary gland is a central endocrine organ regulating basic physiological functions, including growth, the stress response, reproduction, metabolic homeostasis, and lactation. Distinct hormone-producing cell types in the anterior pituitary arise from a common ectodermal primordium during development by extrinsic and intrinsic mechanisms, providing a powerful model system for elucidating general principles in mammalian organogenesis. The central purpose of this review is to inspect the integrated signaling and transcriptional events that affect precursor proliferation, cell lineage commitment, terminal differentiation, and physiological regulation by hypothalamic tropic factors.
Collapse
Affiliation(s)
- Xiaoyan Zhu
- Howard Hughes Medical Institute, Department and School of Medicine, University of California, San Diego, La Jolla, California 92093, USA.
| | | | | |
Collapse
|
25
|
Lim S, Luo M, Koh M, Yang M, bin Abdul Kadir MN, Tan JH, Ye Z, Wang W, Melamed P. Distinct mechanisms involving diverse histone deacetylases repress expression of the two gonadotropin beta-subunit genes in immature gonadotropes, and their actions are overcome by gonadotropin-releasing hormone. Mol Cell Biol 2007; 27:4105-20. [PMID: 17371839 PMCID: PMC1900021 DOI: 10.1128/mcb.00248-07] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are produced in the embryonic pituitary in response to delivery of the hypothalamic gonadotropin releasing hormone (GnRH). GnRH has a pivotal role in reestablishing gonadotropin levels at puberty in primates, and for many species with extended reproductive cycles, these are reinitiated in response to central nervous system-induced GnRH release. Thus, a clear role is evident for GnRH in overcoming repression of these genes. Although the mechanisms through which GnRH actively stimulates LH and FSH beta-subunit (FSHbeta) gene transcription have been described in some detail, there is currently no information on how GnRH overcomes repression in order to terminate reproductively inactive stages. We show here that GnRH overcomes histone deacetylase (HDAC)-mediated repression of the gonadotropin beta-subunit genes in immature gonadotropes. The repressive factors associated with each of these genes comprise distinct sets of HDACs and corepressors which allow for differentially regulated derepression of these two genes, produced in the same cell by the same regulatory hormone. We find that GnRH activation of calcium/calmodulin-dependent protein kinase I (CaMKI) plays a crucial role in the derepression of the FSHbeta gene involving phosphorylation of several class IIa HDACs associated with both the FSHbeta and Nur77 genes, and we propose a model for the mechanisms involved. In contrast, derepression of the LH beta-subunit gene is not CaMK dependent. This demonstration of HDAC-mediated repression of these genes could explain the temporal shut-down of reproductive function at certain periods of the life cycle, which can easily be reversed by the actions of the hypothalamic regulatory hormone.
Collapse
Affiliation(s)
- Stefan Lim
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117542, Republic of Singapore
| | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Melamed P, Kadir MNA, Wijeweera A, Seah S. Transcription of gonadotropin beta subunit genes involves cross-talk between the transcription factors and co-regulators that mediate actions of the regulatory hormones. Mol Cell Endocrinol 2006; 252:167-83. [PMID: 16644099 DOI: 10.1016/j.mce.2006.03.024] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The gonadotropins LH and FSH have distinct temporal patterns of expression as a result of differential regulation by hormones such as GnRH, steroids and activin. This specific regulation is due to diverse sets of transcription factors that are recruited to the promoters of these genes, and recruit specific co-activator complexes which function to stabilize interactions with the general transcription factors and RNA polymerase II, and also to induce covalent modifications of the histone tails at these gene loci. As these molecular mechanisms are elucidated, the nature of nuclear cross-talk between the various hormonally induced pathways is becoming evident, revealing both negative and positive effects of interacting transcription factors and co-regulators. This paper will review current knowledge on the transcriptional regulation of gonadotropin beta subunit gene expression in the chromatin setting, and will present new data pertaining to nuclear cross-talk between the various endocrine-induced pathways regulating gonadotropin gene transcription.
Collapse
Affiliation(s)
- P Melamed
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117542, Singapore.
| | | | | | | |
Collapse
|
27
|
Kumar TR, Schuff KG, Nusser KD, Low MJ. Gonadotroph-specific expression of the human follicle stimulating hormone beta gene in transgenic mice. Mol Cell Endocrinol 2006; 247:103-15. [PMID: 16414183 DOI: 10.1016/j.mce.2005.12.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 11/29/2005] [Accepted: 12/01/2005] [Indexed: 10/25/2022]
Abstract
A paucity of in vitro models has hampered studies of molecular mechanisms of FSH subunit gene expression. Consequently, we used an in vivo transgenic strategy to map the location of regulatory elements in the cloned 10 kb human FSHbeta gene. Analyses of transgenic mouse lines revealed that successive 5' truncations of the hFSHbeta promoter region to -350 bp relative to the transcriptional initiation site retained gonadotroph-specific expression and the sexually dimorphic pattern of male greater than female FSHbeta mRNA levels found normally in rodent pituitary. Truncation of the 3' flanking sequences from positions +3142 to +2138 bp relative to the translational stop codon in exon 3 resulted in a complete loss of transgene expression, suggesting the presence of critical regulatory elements mapping to the 1 kb genomic segment downstream of position +2138, in addition to the proximal 5' promoter elements. In silico phylogenetic comparisons of mammalian FSHbeta genes revealed five islands of highly conserved sequence homology corresponding precisely to the proximal 5' promoter region, exon 2, the 5' translated region of exon 3, and two regions at the 3' untranslated end of exon 3 that include putative polyadenylation and transcriptional termination signals. Sequence analyses of the 5' proximal promoter revealed the presence of several putative homeodomain binding sites as well as GATA, SMAD, AP-1, NF-1, NF-Y and steroid hormone transcription factor binding sites within the highly conserved -350 bp promoter region. Notably absent from these 5' sequences, however, are consensus binding sites for either Egr-1 or Lim-2 transcription factors known to be critical for the gonadotroph-specific expression of the LHbeta gene. These findings support the hypothesis that one of the mechanisms underlying the differential regulation of the LHbeta, FSHbeta, and common alpha-gonadotropin subunits within pituitary gonadotrophs may be differences in sequence-specific binding requirements for distinct combinations of transcription factors.
Collapse
Affiliation(s)
- T Rajendra Kumar
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
| | | | | | | |
Collapse
|
28
|
Aikawa S, Kato T, Susa T, Tomizawa K, Ogawa S, Kato Y. Pituitary transcription factor Prop-1 stimulates porcine follicle-stimulating hormone beta subunit gene expression. Biochem Biophys Res Commun 2004; 324:946-52. [PMID: 15474519 DOI: 10.1016/j.bbrc.2004.09.124] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2004] [Indexed: 10/26/2022]
Abstract
Molecular cloning of the transcription factor that modulates the expression of porcine follicle-stimulating hormone beta subunit (FSHbeta) gene was performed by the yeast one-hybrid cloning system using the -852/-746 upstream region (Fd2) as a bait sequence. We eventually cloned a pituitary transcription factor, Prop-1, which has been identified as an upstream transcription factor of Pit-1 gene. Binding ability of Prop-1 to the bait sequence was confirmed using recombinant Prop-1, and the binding property was investigated by DNase I footprinting, revealing that Prop-1 certainly bound to the large AT-rich region throughout the Fd2. Co-transfection of Prop-1 expression vector together with a reporter gene fused with Fd2 in CHO cells demonstrated an attractive stimulation of reporter gene expression. Immunohistochemistry of adult porcine pituitary confirmed the colocalization of the Prop-1 and FSHbeta subunit. This study is the first to report that Prop-1 participates in the regulation of FSHbeta gene. The present finding will provide new insights into the development of pituitary cell lineage and combined pituitary hormone deficiency (CPHD), since why the defect of Prop-1 causes CPHD including gonadotropins (FSH and LH) has yet to be clarified.
Collapse
Affiliation(s)
- Satoko Aikawa
- Laboratory of Molecular Biology and Gene Regulation, Department of Life Science, School of Agriculture, Meiji University, Kanagawa 214-8571, Japan
| | | | | | | | | | | |
Collapse
|
29
|
Schubert SW, Kardash E, Khan MA, Cheusova T, Kilian K, Wegner M, Hashemolhosseini S. Interaction, cooperative promoter modulation, and renal colocalization of GCMa and Pitx2. J Biol Chem 2004; 279:50358-65. [PMID: 15385555 DOI: 10.1074/jbc.m404587200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The transcription factor GCMa is a member of a new small family of transcription factors with a conserved zinc-containing DNA-binding domain. All members of this transcription factor family play crucial roles as master regulators during development. GCMa is restricted to placenta during development and to kidney and thymus at postnatal stages. It is essential for the formation of the placental labyrinth and as a consequence for survival of the embryo from mid-embryogenesis onwards. Here, we identify Pitx transcription factors as GCMa-interacting proteins. We show that Pitx proteins interact via their conserved homeodomain with the DNA-binding domain of GCMa. As a consequence, Pitx proteins and GCMa exhibit cooperative DNA binding. Furthermore, Pitx proteins influence GCMa-dependent promoter activation in a cell-specific manner. One of the three Pitx paralogues in mice, Pitx2, is the predominant Pitx member present in the placenta and colocalizes on the cellular level with GCMa in the kidney. This is the first description of a regulatory cross-talk between a transcription factor of the GCM family and a homeodomain protein.
Collapse
Affiliation(s)
- Steffen W Schubert
- Institut für Biochemie, Universität Erlangen-Nürnberg, Fahrstrasse 17, D-91054 Erlangen, Germany
| | | | | | | | | | | | | |
Collapse
|
30
|
West BE, Parker GE, Savage JJ, Kiratipranon P, Toomey KS, Beach LR, Colvin SC, Sloop KW, Rhodes SJ. Regulation of the follicle-stimulating hormone beta gene by the LHX3 LIM-homeodomain transcription factor. Endocrinology 2004; 145:4866-79. [PMID: 15271874 DOI: 10.1210/en.2004-0598] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
FSH is a critical hormone regulator of gonadal function that is secreted from the pituitary gonadotrope cell. Human patients and animal models with mutations in the LHX3 LIM-homeodomain transcription factor gene exhibit complex endocrine diseases, including reproductive disorders with loss of FSH. We demonstrate that in both heterologous and pituitary gonadotrope cells, specific LHX3 isoforms activate the FSH beta-subunit promoter, but not the proximal LHbeta promoter. The related LHX4 mammalian transcription factor can also induce FSHbeta promoter transcription, but the homologous Drosophila protein LIM3 cannot. The actions of LHX3 are specifically blocked by a dominant negative LHX3 protein containing a Kruppel-associated box domain. Six LHX3-binding sites were characterized within the FSHbeta promoter, including three within a proximal region that also mediates gene regulation by other transcription factors and activin. Mutations of the proximal binding sites demonstrate their importance for LHX3 induction of the FSHbeta promoter and basal promoter activity in gonadotrope cells. Using quantitative methods, we show that the responses of the FSHbeta promoter to activin do not require induction of the LHX3 gene. By comparative genomics using the human FSHbeta promoter, we demonstrate structural and functional conservation of promoter induction by LHX3. We conclude that the LHX3 LIM homeodomain transcription factor is involved in activation of the FSH beta-subunit gene in the pituitary gonadotrope cell.
Collapse
Affiliation(s)
- Brooke E West
- Department of Biology, Indiana University-Purdue University, 723 West Michigan Street, Indianapolis, Indiana 46202-5132, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Kam KY, Jeong KH, Norwitz ER, Jorgensen EM, Kaiser UB. Oct-1 and nuclear factor Y bind to the SURG-1 element to direct basal and gonadotropin-releasing hormone (GnRH)-stimulated mouse GnRH receptor gene transcription. Mol Endocrinol 2004; 19:148-62. [PMID: 15388790 DOI: 10.1210/me.2004-0025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The cis-regulatory element localized to position -292/-285 of the mouse GnRH receptor (mGnRHR) gene promoter, designated Sequence Underlying Responsiveness to GnRH 1 (SURG-1), has been shown previously to contribute to stimulation of mGnRHR gene expression by GnRH. We have identified three specific protein-DNA complexes on the SURG-1 element by EMSA using nuclear extracts from the gonadotrope-derived alphaT3-1 and LbetaT2 cell lines. Serial mutagenesis and supershift assays identified nuclear factor Y (NF-Y) binding to -288/-284 and Oct-1 binding to a TAAT sequence at -290/-287. Binding of these two transcription factors was confirmed in vivo by chromatin immunoprecipitation assay and increased in response to GnRH stimulation. To define the functional significance of these sequences in the regulation of mGnRHR gene transcription, transient transfection assays were performed in alphaT3-1 cells using a 1.2-kb mGnRHR (-1164/+62) gene promoter-luciferase reporter construct with selective mutations of the Oct-1, NF-Y, and/or the previously characterized activating protein 1 (AP-1) binding site (-274/-268). Individual mutations in the Oct-1, NF-Y, and AP-1 sites decreased both basal expression and stimulation by GnRH agonist, and the combined mutation of the Oct-1 and AP-1 binding sites further reduced basal transcriptional activity and abolished GnRH stimulation. Overexpression of NF-YA increased GnRHR promoter activity, whereas expression of a dominant negative NF-YA mutant decreased activity, further supporting a role of NF-Y in regulation of mGnRHR gene transcription. In addition, knockdown of Oct-1 by small interfering RNA confirmed that Oct-1 is important for mGnRHR gene expression. In conclusion, NF-Y and Oct-1 bind to the SURG-1 element to direct basal and GnRH-stimulated expression of the mGnRHR gene.
Collapse
Affiliation(s)
- Kyung-Yoon Kam
- Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 221 Longwood Avenue, Boston, Massachusetts 02115, USA
| | | | | | | | | |
Collapse
|
32
|
Jeong KH, Chin WW, Kaiser UB. Essential role of the homeodomain for pituitary homeobox 1 activation of mouse gonadotropin-releasing hormone receptor gene expression through interactions with c-Jun and DNA. Mol Cell Biol 2004; 24:6127-39. [PMID: 15226417 PMCID: PMC434250 DOI: 10.1128/mcb.24.14.6127-6139.2004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Revised: 10/21/2003] [Accepted: 02/23/2004] [Indexed: 11/20/2022] Open
Abstract
The gonadotropin-releasing hormone receptor (GnRHR) is expressed primarily in the gonadotropes of the anterior pituitary. Pituitary homeobox 1 (Pitx-1) has been shown to activate pituitary-specific gene expression by direct DNA binding and/or protein-protein interaction with other transcription factors. We hypothesized that Pitx-1 might also dictate tissue-specific expression of the mouse GnRHR (mGnRHR) gene in a similar manner. Pitx-1 activated the mGnRHR gene promoter, and transactivation was localized to sequences between -308 and -264. Pitx-1 bound to this region only with low affinity. This region includes an activating protein 1 (AP-1) site, which was previously shown to be important for mGnRHR gene expression. Further characterization indicated that an intact AP-1 site was required for full Pitx-1 responsiveness. Furthermore, Pitx-1 and AP-1 were synergistic in the activation of the mGnRHR gene promoter. A Pitx-1 homeodomain (HD) point mutation, which eliminated DNA binding ability, caused only a partial reduction of transactivation, whereas deletion of the HD completely prevented transactivation. Pitx-1 interacted directly with c-Jun, and the HD was sufficient for this interaction. While the point mutation in the Pitx-1 HD did not affect interaction with c-Jun, deletion of the HD eliminated the interaction. Taken together, our studies indicate that Pitx-1 can direct transactivation of the mGnRHR gene, in part by DNA binding and in part by an action of Pitx-1 as a cofactor for AP-1, augmenting AP-1 activity through a novel protein-protein interaction between c-Jun and the HD of Pitx-1.
Collapse
Affiliation(s)
- Kyeong-Hoon Jeong
- Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | | | | |
Collapse
|
33
|
Savage JJ, Yaden BC, Kiratipranon P, Rhodes SJ. Transcriptional control during mammalian anterior pituitary development. Gene 2004; 319:1-19. [PMID: 14597167 DOI: 10.1016/s0378-1119(03)00804-7] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The mammalian anterior pituitary gland is a compound endocrine organ that regulates reproductive development and fitness, growth, metabolic homeostasis, the response to stress, and lactation, by actions on target organs such as the gonads, the liver, the thyroid, the adrenals, and the mammary gland. The protein and peptide hormones that control these physiological parameters are secreted by specialized pituitary cell types that derive from a common origin in the early ectoderm. Collectively, the broad physiological importance of the pituitary gland, its intriguing organogenesis, and the clinical and agricultural significance of its actions, have established pituitary development as an excellent model system for the study of the gene-regulatory cascades that guide vertebrate cell determination and differentiation. We review the transcriptional pathways that regulate the commitment of the individual pituitary cell lineages and that subsequently modulate trophic hormone gene activity in the differentiated cells of the mature gland.
Collapse
Affiliation(s)
- Jesse J Savage
- Department of Biology, Indiana University Center for Regenerative Biology and Medicine, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202-5132, USA
| | | | | | | |
Collapse
|
34
|
Chong KL, Wang S, Melamed P. Isolation and characterization of the follicle-stimulating hormone beta subunit gene and 5' flanking region of the Chinook salmon. Neuroendocrinology 2004; 80:158-70. [PMID: 15583473 DOI: 10.1159/000082357] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2004] [Accepted: 08/19/2004] [Indexed: 11/19/2022]
Abstract
In this study we have isolated the follicle-stimulating hormone beta subunit gene from the Chinook salmon (csFSHbeta). This gene encodes for a protein that is highly similar to those isolated from other salmonids and shares all of the structural constraints seen in mammalian gonadotropins, including twelve conserved cysteines and a putative N-linked glycosylation site. The organization of the gene follows the conserved pattern regarding the numbers and positions of the introns, although the csFSHbeta gene contains a particularly large 6.2-kb first intron due to the inclusion of several transposon-like elements. Isolation of 1.2 kb of the 5' flanking region of the csFSHbeta gene and subsequent analysis in silico have revealed a number of putative elements which appear highly conserved in teleost FSHbeta gene promoters and are thus likely involved in basal and hormone-induced transcriptional regulation. The functionality of this 1.2-kb fragment in driving expression of a reporter gene and its response to GnRH was shown in gonadotropes, while the overexpression of AP-1 factors, Sf-1, estrogen receptor or Smad1 revealed that the promoter is responsive to these transcription factors. Our current study has opened the way for future analysis to verify the role of these factors in mediating hormonally induced transcription of this gene.
Collapse
Affiliation(s)
- Kok Leong Chong
- Functional Genomics Laboratories, Department of Biological Sciences, National University of Singapore, Singapore
| | | | | |
Collapse
|
35
|
Jacobs SBR, Coss D, McGillivray SM, Mellon PL. Nuclear factor Y and steroidogenic factor 1 physically and functionally interact to contribute to cell-specific expression of the mouse Follicle-stimulating hormone-beta gene. Mol Endocrinol 2003; 17:1470-83. [PMID: 12730328 PMCID: PMC2933173 DOI: 10.1210/me.2002-0286] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
FSH is a heterodimeric glycoprotein hormone secreted from the gonadotrope cell population of the anterior pituitary. Despite its crucial role in mammalian reproduction, very little is known about regulation of the FSH beta-subunit gene at the molecular level. In this report, we examine the basis for cell-specific expression of FSH beta using the mouse L beta T2 and alpha T3-1 gonadotrope-derived cell lines. Characterization of the hormonal content of L beta T2 and alpha T3-1 cells at the protein level classifies these cells as relatively mature and immature gonadotropes, respectively. We studied L beta T2 cell-specific expression of FSH beta using 398 bp of the mouse FSH beta regulatory region linked to a luciferase reporter gene in transient transfection assays. This mouse FSH beta promoter can direct reporter gene expression specifically to L beta T2 cells when compared with other pituitary- and non-pituitary-derived cell lines, including alpha T3-1 cells. Furthermore, it is induced by activin, and interruption of the autocrine activin loop in L beta T2 cells by the addition of follistatin reduces its expression. Truncation analysis indicates that several regions of the promoter are involved in this specificity and that these can be dissociated from activin regulation. We identify binding sites for the orphan nuclear receptor steroidogenic factor-1 and the heterotrimeric transcription factor nuclear factor Y and show that these elements functionally interact to regulate FSH beta gene expression in an L beta T2 cell-specific manner. Moreover, steroidogenic factor-1 and nuclear factor Y are shown to physically interact with each other. This study is the first to demonstrate the presence of basal FSH beta protein in L beta T2 cells and to identify specific elements within the FSH beta promoter that contribute to basal and cell-specific expression of the gene.
Collapse
Affiliation(s)
- Suzanne B R Jacobs
- Department of Reproductive Medicine, University of California, San Diego, La Jolla, California 92093-0674, USA
| | | | | | | |
Collapse
|
36
|
Suszko MI, Lo DJ, Suh H, Camper SA, Woodruff TK. Regulation of the rat follicle-stimulating hormone beta-subunit promoter by activin. Mol Endocrinol 2003; 17:318-32. [PMID: 12554780 DOI: 10.1210/me.2002-0081] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
FSH is controlled by a variety of positive and negative stimuli, and the unique FSHbeta-subunit is a major target for this regulation. Activin is a key modulator of FSHbeta transcription and hormone secretion. The signal transduction pathway leading to FSH expression was previously unknown. Here, we show that the transcription factors Smad3 and Smad4 mediate activin-stimulated activity of the rat FSHbeta promoter in a pituitary-derived cell line, LbetaT2. Cells were transiently transfected with the rat FSHbeta promoter fused to a luciferase reporter gene (-338rFSHbeta-Luc), and a minimal activin-responsive region was identified. Transfection of Smad3, but not the highly related Smad2, led to a ligand-independent stimulation of the FSHbeta promoter activity. As expected, activin caused an additional increase of luciferase expression, which was blocked by cotreatment with follistatin. Although Smad4 alone had no effect on FSHbeta transcription, it significantly augmented Smad3 and activin-mediated stimulation of the promoter. A palindromic consensus Smad-binding element in the proximal promoter was found to bind Smad4, and elimination of the region resulted in a loss of activin-mediated FSHbeta transcription. The activin signaling pathway is conserved in a number of cells, but FSHbeta expression is restricted to gonadotropes. A pituitary-specific transcription factor necessary for activin-dependent induction of the FSHbeta promoter has been identified that permits FSHbeta expression in nongonadotrope cells. Pitx2 is a member of Pitx subfamily of bicoid-related homeodomain factors that is required for pituitary development and is present in the adult pituitary. This factor was transfected into LbetaT2 cells, where it caused up-regulation of basal and activin-mediated FSHbeta promoter activity. Furthermore, cotransfection of Pitx2c with Smad3 in kidney-derived TSA cells resulted in activin-regulated FSHbeta response, suggesting its important role in tissue-restricted regulation of FSHbeta by activin. A Pitx2c binding site was identified within the proximal promoter, and elimination of this region also resulted in a loss of activin-regulated FSHbeta promoter activity. Taken together, these studies suggest that the regulation of FSHbeta is dependent on activin-mediated signaling factors in concert with pituitary-derived nuclear regulatory proteins.
Collapse
Affiliation(s)
- Magdalena I Suszko
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA
| | | | | | | | | |
Collapse
|