Identifying growth hormone-regulated enhancers in the Igf1 locus

Growth hormone (GH) plays a central role in regulating somatic growth and in controlling multiple physiological processes in humans and other vertebrates. A key agent in many GH actions is the secreted peptide, IGF-I. As established previously, GH stimulates IGF-I gene expression via the Stat5b transcription factor, leading to production of IGF-I mRNAs and proteins. However, the precise mechanisms by which GH-activated Stat5b promotes IGF-I gene transcription have not been defined. Unlike other GH-regulated genes, there are no Stat5b sites near either of the two IGF-I gene promoters. Although dispersed GH-activated Stat5b binding elements have been mapped in rodent Igf1 gene chromatin, it is unknown how these distal sites might function as potential transcriptional enhancers. Here we have addressed mechanisms of regulation of IGF-I gene transcription by GH by generating cell lines in which the rat Igf1 chromosomal locus has been incorporated into the mouse genome. Using these cells we find that physiological levels of GH rapidly and potently activate Igf1 gene transcription while stimulating physical interactions in chromatin between inducible Stat5b-binding elements and the Igf1 promoters. We have thus developed a robust experimental platform for elucidating how dispersed transcriptional enhancers control Igf1 gene expression under different biological conditions.

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Differential effects of STAT proteins on growth hormone-mediated IGF-I gene expression

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00324.2014 ◽

2014 ◽

Vol 307 (9) ◽

pp. E847-E855 ◽

Cited By ~ 10

Author(s):

Ben Varco-Merth ◽

Peter Rotwein

Keyword(s):

Growth Hormone ◽

Gene Transcription ◽

Cultured Cells ◽

Somatic Growth ◽

Functional Responses ◽

Stat Proteins ◽

Gene And Protein Expression ◽

Igf I ◽

I Gene

Growth hormone (GH) plays a key role regulating somatic growth and in controlling metabolism and other physiological processes in humans and other animal species. GH acts by binding to the extracellular part of its transmembrane receptor, leading to induction of multiple intracellular signal transduction pathways that culminate in changes in gene and protein expression. A key agent in GH-stimulated growth is the latent transcription factor signal transducer and activator of transcription (STAT) 5B, one of four STAT proteins induced by the GH receptor in cultured cells and in vivo. As shown by genetic and biochemical studies, GH-activated STAT5B promotes transcription of the gene encoding the critical growth peptide, insulin-like growth factor-I (IGF-I), and natural null mutations of STAT5B in humans lead to growth failure accompanied by diminished IGF-I expression. Here we have examined the possibility that other GH-activated STATs can enhance IGF-I gene transcription, and thus potentially contribute to GH-regulated somatic growth. We find that human STAT5A is nearly identical to STAT5B in its biochemical and functional responses to GH but that STAT1 and STAT3 show a weaker profile of in vitro binding to STAT DNA elements from the IGF-I gene than STAT5B, and are less potent inducers of gene transcription through these elements. Taken together, our results offer a molecular explanation for why STAT5B is a key in vivo mediator of GH-activated IGF-I gene transcription and thus of GH-regulated somatic growth.

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Effect of exogenous chicken growth hormone (cGH) administration on insulin-like growth factor-I (IGF-I) gene expression in domestic fowl

Molecular and Cellular Endocrinology ◽

10.1016/0303-7207(95)96796-k ◽

1995 ◽

Vol 114 (1-2) ◽

pp. 157-166 ◽

Cited By ~ 29

Author(s):

G Rosselot

Keyword(s):

Gene Expression ◽

Growth Hormone ◽

Growth Factor ◽

Domestic Fowl ◽

Insulin Like Growth Factor ◽

Factor I ◽

Igf I ◽

Growth Factor I ◽

I Gene

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20kDa Human Growth Hormone (20K hGH) Stimulates Insulin-Like Growth Factor-I (IGF-I) Gene Expression at Lower Concentrations than 22K hGH in hGH Receptor-Expressing Ba/F3 Cells

Endocrine Journal ◽

10.1507/endocrj.47.supplmarch_s37 ◽

2000 ◽

Vol 47 (SupplMarch) ◽

pp. S37-S40 ◽

Cited By ~ 3

Author(s):

HIDEO YOSHIZATO ◽

MINORU TANAKA ◽

TAKAHIKO FUJIKAWA ◽

YOSHIFUMI HIGASHIMOTO ◽

AYAKO SHIMIZU ◽

...

Keyword(s):

Gene Expression ◽

Growth Hormone ◽

Growth Factor ◽

Human Growth Hormone ◽

Human Growth ◽

Insulin Like Growth Factor ◽

Factor I ◽

Igf I ◽

Growth Factor I ◽

I Gene

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Tumor necrosis factor inhibits growth hormone-mediated gene expression in hepatocytes

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00550.2005 ◽

2006 ◽

Vol 291 (1) ◽

pp. G35-G44 ◽

Cited By ~ 14

Author(s):

Tamer Ahmed ◽

Gladys Yumet ◽

Margaret Shumate ◽

Charles H. Lang ◽

Peter Rotwein ◽

...

Keyword(s):

Gene Expression ◽

Growth Hormone ◽

Mrna Expression ◽

Gene Transcription ◽

Protein Tyrosine Phosphatases ◽

Mrna Levels ◽

Inhibitory Effects ◽

Protein Levels ◽

Mrna Induction ◽

Igf I

Growth hormone (GH) stimulates STAT5 phosphorylation by JAK2, which activates IGF-I and serine protease inhibitor 2.1 (Spi 2.1) transcription, whereas STAT5 dephosphorylation by protein tyrosine phosphatases (PTPs) terminates this signal. We hypothesized that the inhibitory effects of TNF on GH signaling and gene transcription were responsible for hepatic GH resistance. CWSV-1 hepatocytes were treated with TNF, pervanadate (a PTP inhibitor), or both, before GH stimulation. Total and tyrosine-phosphorylated JAK2, STAT5, ERK1/2, SHP-1 and SHP-2, IGF-I, and Spi 2.1 mRNA levels were measured. GH stimulated STAT5 and ERK1/2 phosphorylation, IGF-I, and Spi 2.1 mRNA expression. TNF attenuated JAK2/STAT5 and ERK1/2 phosphorylation and IGF-I and Spi 2.1 mRNA expression following GH stimulation. SHP-1 and SHP-2 protein levels were unaltered by TNF or GH, and the GH-induced increase in SHP-1 PTP activity was not further increased by TNF. In TNF-treated cells, pervanadate restored STAT5 and ERK1/2 phosphorylation to control levels following GH stimulation but did not restore IGF-I or Spi 2.1 mRNA induction. Cells transfected with a Spi 2.1 promoter-luciferase vector demonstrate a 50-fold induction in luciferase activity following GH stimulation or cotransfection with a constitutively active STAT5 vector. TNF prevented the induction of Spi 2.1 promoter activity by GH and the STAT5 construct. We conclude that TNF does not inhibit GH activity by inducing SHP-1 or -2 expression and that correction of GH signaling defects in TNF-treated cells by pervanadate does not restore GH-induced gene expression. The inhibitory effects of TNF on GH-mediated gene transcription appear independent of STAT5 activity and previously identified abnormalities in JAK2/STAT5 signaling.

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In vivo regulation of growth hormone-stimulated gene transcription by STAT5b

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00389.2003 ◽

2004 ◽

Vol 286 (3) ◽

pp. E393-E401 ◽

Cited By ~ 66

Author(s):

Joachim Woelfle ◽

Peter Rotwein

Keyword(s):

Gene Expression ◽

Signal Transduction ◽

Growth Hormone ◽

Gene Transfer ◽

Gene Transcription ◽

Dominant Negative ◽

Signal Transduction Pathways ◽

Igf I ◽

Igfbp 3

The long-term effects of growth hormone (GH) are mediated through coordinated changes in gene expression that are the outcome of interactions between hormone-activated signal transduction pathways and specific feedback loops. Recent studies in mice have implicated the transcription factor STAT5b as part of the GH-regulated somatic growth pathway, because mice lacking this protein showed diminished growth rates. To assess the role of Stat5b in GH-stimulated gene expression, we have delivered modified versions of the protein to the liver of pituitary-deficient male rats by quantitative adenovirus-mediated gene transfer. In pilot studies in cell culture, both constitutive-active and dominant-negative STAT5b showed appropriate binding properties toward a specific DNA response element. After in vivo expression, neither protein prevented nuclear accumulation of STATs 1 and 3 in the liver. Dominant-negative STAT5b completely inhibited GH-stimulated transcription of genes encoding the growth-promoting proteins IGF-I, IGF-binding protein-3 (IGFBP-3), and acid-labile subunit (ALS), which comprise the major circulating IGF-I complex, and blocked expression of the GH inhibitors SOCS-1, SOCS-2, and CIS, but had little effect on induction of SOCS-3. Constitutive-active STAT5b stimulated robust transcription of IGF-I, ALS, and IGFBP-3 in the absence of hormone but did little to modify GH-mediated activation of SOCS family genes. An adenovirus encoding EGFP was without effect. These results, in addition to establishing STAT5b as one of the key agents of GH-stimulated gene transcription, demonstrate the feasibility of using in vivo gene transfer to target and dissect the functions of distinct components of complex hormone-activated signal transduction pathways.

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Growth Hormone-Activated STAT5 May Indirectly Stimulate IGF-I Gene Transcription through HNF-3γ

Molecular Endocrinology ◽

10.1210/me.2009-0178 ◽

2009 ◽

Vol 23 (12) ◽

pp. 2026-2037 ◽

Cited By ~ 16

Author(s):

Satyanarayana Eleswarapu ◽

Xiaomei Ge ◽

Ying Wang ◽

Jie Yu ◽

Honglin Jiang

Keyword(s):

Growth Hormone ◽

Gene Transcription ◽

Igf I ◽

I Gene

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Control of ovine hepatic growth hormone receptor and insulin-like growth factor I by thyroid hormones in utero

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2000.278.6.e1166 ◽

2000 ◽

Vol 278 (6) ◽

pp. E1166-E1174 ◽

Cited By ~ 14

Author(s):

A. J. Forhead ◽

J. Li ◽

J. C. Saunders ◽

M. J. Dauncey ◽

R. S. Gilmour ◽

...

Keyword(s):

Gene Expression ◽

Growth Hormone ◽

Growth Factor ◽

Thyroid Hormones ◽

Hormone Receptor ◽

Growth Hormone Receptor ◽

Insulin Like Growth Factor ◽

Factor I ◽

Igf I ◽

I Gene

By use of RNase protection assays, hepatic growth hormone receptor (GHR) and insulin-like growth factor I (IGF-I) mRNA abundances were measured in sheep fetuses after experimental manipulation of fetal plasma thyroid hormone concentrations by fetal thyroidectomy (TX) and exogenous infusion of triiodothyronine (T3) and cortisol. TX abolished the normal prepartum rise in hepatic GHR abundance but had little effect on hepatic GHR gene expression at 127–130 days (term 145 ± 2 days). By contrast, it upregulated basal IGF-I expression in immature fetal liver by increasing both Class 1 and Class 2 transcript abundance but had no further effects on IGF-I gene mRNA levels at 142–145 days. Raising plasma T3 to prepartum values by exogenous infusion of either T3 or cortisol into immature intact fetuses prematurely raised hepatic GHR and IGF-I mRNA abundances to values similar to those seen in intact fetuses at 142–145 days. In TX fetuses, cortisol infusion increased hepatic GHR mRNA but not total IGF-I mRNA abundance at 127–130 days. These findings show that thyroid hormones have an important role in the regulation of hepatic GHR and IGF-I gene expression in fetal sheep during late gestation and suggest that T3 mediates the maturational effects of cortisol on the hepatic somatotropic axis close to term.

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Identification of the cDNA Encoding the Growth Hormone Receptor (GHR) and the Regulation of GHR and IGF-I Gene Expression by Nutritional Status in Reeves’ Turtle (Chinemys reevesii)

Frontiers in Genetics ◽

10.3389/fgene.2020.00587 ◽

2020 ◽

Vol 11 ◽

Author(s):

Wenlu Zhu ◽

Yuhui He ◽

Zhuohao Ruan ◽

Xiquan Zhang ◽

Liangyuan Liao ◽

...

Keyword(s):

Gene Expression ◽

Growth Hormone ◽

Nutritional Status ◽

Hormone Receptor ◽

Growth Hormone Receptor ◽

Igf I ◽

I Gene

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Growth hormone stimulates IGF I gene expression in isolated rat renal collecting duct

AJP Renal Physiology ◽

10.1152/ajprenal.1990.259.3.f474 ◽

1990 ◽

Vol 259 (3) ◽

pp. F474-F479 ◽

Cited By ~ 1

Author(s):

S. A. Rogers ◽

S. B. Miller ◽

M. R. Hammerman

Keyword(s):

Gene Expression ◽

Growth Hormone ◽

Plasma Membranes ◽

Collecting Duct ◽

Dependent Manner ◽

Collecting Ducts ◽

Igf I ◽

Renal Collecting Duct ◽

I Gene

To determine whether growth hormone (GH) directly stimulates insulin-like growth factor I (IGF I) gene expression in renal collecting duct, plasma membranes prepared from collecting ducts isolated from rat kidney, and collecting ducts themselves were incubated in presence and absence of GH. GH enhanced phospholipase C activity in collecting duct plasma membranes establishing the potential for GH-signal transduction. Inclusion of GH in suspensions of collecting ducts increased production of immunoreactive IGF I in a time-dependent and concentration-dependent manner. Production was stimulated significantly by addition of 10(-10), 10(-8), or 10(-6) M GH to suspensions for 2 h. IGF I produced in isolated collecting ducts was released into the suspending media. Levels of IGF I mRNA in collecting ducts were increased 2.8-fold after incubation with 10(-6) M GH in vitro. IGF I of collecting duct origin was indistinguishable from recombinant human IGF I in terms of its size and receptor-binding characteristics. Our findings demonstrate a direct action of GH to enhance collecting duct IGF I gene expression in vitro. Such enhancement is likely to reflect the mechanism by which GH stimulates renal IGF I production in intact kidney.

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