Publications by authors named "Sergei G Tevosian"

25 Publications

  • Page 1 of 1

Targeting pheochromocytoma/paraganglioma with polyamine inhibitors.

Metabolism 2020 09 18;110:154297. Epub 2020 Jun 18.

Department of Medicine, Division of Endocrinology, University of Florida and Malcom Randall VA Medical Center, Gainesville, FL, USA. Electronic address:

Background: Pheochromocytomas (PCCs) and paragangliomas (PGLs) are neuroendocrine tumors that are mostly benign. Metastatic disease does occur in about 10% of cases of PCC and up to 25% of PGL, and for these patients no effective therapies are available. Patients with mutations in the succinate dehydrogenase subunit B (SDHB) gene tend to have metastatic disease. We hypothesized that a down-regulation in the active succinate dehydrogenase B subunit should result in notable changes in cellular metabolic profile and could present a vulnerability point for successful pharmacological targeting.

Methods: Metabolomic analysis was performed on human hPheo1 cells and shRNA SDHB knockdown hPheo1 (hPheo1 SDHB KD) cells. Additional analysis of 115 human fresh frozen samples was conducted. In vitro studies using N,N-diethylnorspermine (DENSPM) and N,N- diethylspermine (DESPM) treatments were carried out. DENSPM efficacy was assessed in human cell line derived mouse xenografts.

Results: Components of the polyamine pathway were elevated in hPheo1 SDHB KD cells compared to wild-type cells. A similar observation was noted in SDHx PCC/PGLs tissues compared to their non-mutated counterparts. Specifically, spermidine, and spermine were significantly elevated in SDHx-mutated PCC/PGLs, with a similar trend in hPheo1 SDHB KD cells. Polyamine pathway inhibitors DENSPM and DESPM effectively inhibited growth of hPheo1 cells in vitro as well in mouse xenografts.

Conclusions: This study demonstrates overactive polyamine pathway in PCC/PGL with SDHB mutations. Treatment with polyamine pathway inhibitors significantly inhibited hPheo1 cell growth and led to growth suppression in xenograft mice treated with DENSPM. These studies strongly implicate the polyamine pathway in PCC/PGL pathophysiology and provide new foundation for exploring the role for polyamine analogue inhibitors in treating metastatic PCC/PGL. PRéCIS: Cell line metabolomics on hPheo1 cells and PCC/PGL tumor tissue indicate that the polyamine pathway is activated. Polyamine inhibitors in vitro and in vivo demonstrate that polyamine inhibitors are promising for malignant PCC/PGL treatment. However, further research is warranted.
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http://dx.doi.org/10.1016/j.metabol.2020.154297DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7482423PMC
September 2020

Molecular Mechanisms of Primary Aldosteronism.

Endocrinol Metab (Seoul) 2019 12;34(4):355-366

Division of Endocrinology, Department of Medicine, Malcom Randall VA Medical Center, University of Florida, Gainesville, FL, USA.

Primary aldosteronism (PA) results from excess production of mineralocorticoid hormone aldosterone by the adrenal cortex. It is normally caused either by unilateral aldosterone-producing adenoma (APA) or by bilateral aldosterone excess as a result of bilateral adrenal hyperplasia. PA is the most common cause of secondary hypertension and associated morbidity and mortality. While most cases of PA are sporadic, an important insight into this debilitating disease has been derived through investigating the familial forms of the disease that affect only a minor fraction of PA patients. The advent of gene expression profiling has shed light on the genes and intracellular signaling pathways that may play a role in the pathogenesis of these tumors. The genetic basis for several forms of familial PA has been uncovered in recent years although the list is likely to expand. Recently, the work from several laboratories provided evidence for the involvement of mammalian target of rapamycin pathway and inflammatory cytokines in APAs; however, their mechanism of action in tumor development and pathophysiology remains to be understood.
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http://dx.doi.org/10.3803/EnM.2019.34.4.355DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6935778PMC
December 2019

Pheochromocytomas and Paragangliomas.

Endocrinol Metab Clin North Am 2019 12;48(4):727-750

Department of Medicine, Division of Endocrinology, University of Florida, Malcom Randall VA Medical Center, Gainesville, FL 32610, USA. Electronic address:

Pheochromocytomas are rare neuroendocrine tumors. Extra-adrenal lesions arising from the autonomic neural ganglia are termed paraganglioma. Clinical symptoms are common between the adrenal and extra-adrenal forms and are determined by excess secretion of catecholamines. Hypertension is a critical and often dramatic feature of pheochromocytoma/paraganglioma, and its most prevalent reported symptom. However, given the rare occurrence of this cancer, in patients undergoing screening for hypertension, the prevalence ranges from 0.1% to 0.6%. Still, patients frequently come to the attention of endocrinologist when pheochromocytoma/paraganglioma is suspected as a secondary cause of hypertension. This article summarizes current clinical approaches in patients with pheochromocytoma/paraganglioma.
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http://dx.doi.org/10.1016/j.ecl.2019.08.006DOI Listing
December 2019

Pheochromocytoma/Paraganglioma: A Poster Child for Cancer Metabolism.

J Clin Endocrinol Metab 2018 05;103(5):1779-1789

Department of Medicine, Division of Endocrinology, University of Florida, Gainesville, Florida.

Context: Pheochromocytomas (PCCs) are tumors that are derived from the chromaffin cells of the adrenal medulla. Extra-adrenal PCCs called paragangliomas (PGLs) are derived from the sympathetic and parasympathetic chain ganglia. PCCs secrete catecholamines, which cause hypertension and have adverse cardiovascular consequences as a result of catecholamine excess. PGLs may or may not produce catecholamines depending on their genetic type and anatomical location. The most worrisome aspect of these tumors is their ability to become aggressive and metastasize; there are no known cures for metastasized PGLs.

Methods: Original articles and reviews indexed in PubMed were identified by querying with specific PCC/PGL- and Krebs cycle pathway-related terms. Additional references were selected through the in-depth analysis of the relevant publications.

Results: We primarily discuss Krebs cycle mutations that can be instrumental in helping investigators identify key biological pathways and molecules that may serve as biomarkers of or treatment targets for PCC/PGL.

Conclusion: The mainstay of treatment of patients with PCC/PGLs is surgical. However, the tide may be turning with the discovery of new genes associated with PCC/PGLs that may shed light on oncometabolites used by these tumors.
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http://dx.doi.org/10.1210/jc.2017-01991DOI Listing
May 2018

Adrenal Development in Mice Requires GATA4 and GATA6 Transcription Factors.

Endocrinology 2015 Jul 1;156(7):2503-17. Epub 2015 May 1.

Department of Physiological Sciences (S.G.T., E.J., H.M.H., T.J., S.C.F., M.B.P.), College of Veterinary Medicine, University of Florida, Gainesville, Florida 32610-0144; and Department of Applied Physiology and Kinesiology (D.A.M.), College of Health and Human Performance, University of Florida, Gainesville, Florida 32611-8200.

The adrenal glands consist of an outer cortex and an inner medulla, and their primary purposes include hormone synthesis and secretion. The adrenal cortex produces a complex array of steroid hormones, whereas the medulla is part of the sympathetic nervous system and produces the catecholamines epinephrine and norepinephrine. In the mouse, GATA binding protein (GATA) 4 and GATA6 transcription factors are coexpressed in several embryonic tissues, including the adrenal cortex. To explore the roles of GATA4 and GATA6 in mouse adrenal development, we conditionally deleted these genes in adrenocortical cells using the Sf1Cre strain of animals. We report here that mice with Sf1Cre-mediated double deletion of Gata4 and Gata6 genes lack identifiable adrenal glands, steroidogenic factor 1-positive cortical cells and steroidogenic gene expression in the adrenal location. The inactivation of the Gata6 gene alone (Sf1Cre;Gata6(flox/flox)) drastically reduced the adrenal size and corticosterone production in the adult animals. Adrenocortical aplasia is expected to result in the demise of the animal within 2 weeks after birth unless glucocorticoids are provided. In accordance, Sf1Cre;Gata4(flox/flox)Gata6(flox/flox) females depend on steroid supplementation to survive after weaning. Surprisingly, Sf1Cre;Gata4(flox/flox)Gata6(flox/flox) males appear to live normal lifespans as vital steroidogenic synthesis shifts to their testes. Our results reveal a requirement for GATA factors in adrenal development and provide a novel tool to characterize the transcriptional network controlling adrenocortical cell fates.
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http://dx.doi.org/10.1210/en.2014-1815DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4475720PMC
July 2015

Combined loss of the GATA4 and GATA6 transcription factors in male mice disrupts testicular development and confers adrenal-like function in the testes.

Endocrinology 2015 May 10;156(5):1873-86. Epub 2015 Feb 10.

Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida 32610.

The roles of the GATA4 and GATA6 transcription factors in testis development were examined by simultaneously ablating Gata4 and Gata6 with Sf1Cre (Nr5a1Cre). The deletion of both genes resulted in a striking testicular phenotype. Embryonic Sf1Cre; Gata4(flox/flox) Gata6(flox/flox) (conditional double mutant) testes were smaller than control organs and contained irregular testis cords and fewer gonocytes. Gene expression analysis revealed significant down-regulation of Dmrt1 and Mvh. Surprisingly, Amh expression was strongly up-regulated and remained high beyond postnatal day 7, when it is normally extinguished. Neither DMRT1 nor GATA1 was detected in the Sertoli cells of the mutant postnatal testes. Furthermore, the expression of the steroidogenic genes Star, Cyp11a1, Hsd3b1, and Hsd17b3 was low throughout embryogenesis. Immunohistochemical analysis revealed a prominent reduction in cytochrome P450 side-chain cleavage enzyme (CYP11A1)- and 3β-hydroxysteroid dehydrogenase-positive (3βHSD) cells, with few 17α-hydroxylase/17,20 lyase-positive (CYP17A1) cells present. In contrast, in postnatal Sf1Cre; Gata4(flox/flox) Gata6(flox/flox) testes, the expression of the steroidogenic markers Star, Cyp11a1, and Hsd3b6 was increased, but a dramatic down-regulation of Hsd17b3, which is required for testosterone synthesis, was observed. The genes encoding adrenal enzymes Cyp21a1, Cyp11b1, Cyp11b2, and Mcr2 were strongly up-regulated, and clusters containing numerous CYP21A2-positive cells were localized in the interstitium. These data suggest a lack of testis functionality, with a loss of normal steroidogenic testis function, concomitant with an expansion of the adrenal-like cell population in postnatal conditional double mutant testes. Sf1Cre; Gata4(flox/flox) Gata6(flox/flox) animals of both sexes lack adrenal glands; however, despite this deficiency, males are viable in contrast to the females of the same genotype, which die shortly after birth.
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http://dx.doi.org/10.1210/en.2014-1907DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4398756PMC
May 2015

Simultaneous gene deletion of gata4 and gata6 leads to early disruption of follicular development and germ cell loss in the murine ovary.

Biol Reprod 2014 Jul 4;91(1):24. Epub 2014 Jun 4.

Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida

Granulosa cell formation and subsequent follicular assembly are important for ovarian development and function. Two members of the GATA family of transcription factors, GATA4 and GATA6, are expressed in ovarian somatic cells early in development, and their importance in adult ovarian function has been recently highlighted. In this study, we demonstrated that the embryonic loss of Gata4 and Gata6 expression within the ovary results in a strong down-regulation of genes involved in the ovarian developmental pathway (Fst and Irx3) as well as diminished expression of the pregranulosa and granulosa cell markers SPRR2 and FOXL2, respectively. Postnatal ovaries deficient in both Gata genes show impaired somatic cell proliferation and arrested follicular development at the primordial stage, where oocytes are either enclosed by one layer of squamous granulosa cells or remain in germ cell nests/clusters. Furthermore, germ cell nests and primordial follicles are predominantly localized to the central region of the Sf1Cre; Gata4(flox/flox) Gata6(flox/flox) ovaries, where the boundary between the medulla and cortex is almost nonexistent. Lastly, most of the oocytes are lost early in development in conditional double mutant ovaries, which confirms the importance of normally differentiated granulosa cells as supporting cells for oocyte survival. Thus, both GATA4 and GATA6 proteins are fundamental regulators of granulosa cell differentiation and proliferation, and consequently of proper follicular assembly during normal ovarian development and function.
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http://dx.doi.org/10.1095/biolreprod.113.117002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4434962PMC
July 2014

Transgenic mouse models in the study of reproduction: insights into GATA protein function.

Reproduction 2014 Jul 3;148(1):R1-R14. Epub 2014 Apr 3.

Department of Physiological SciencesCollege of Veterinary Medicine, University of Florida, Gainesville, Florida 32610, USA

For the past 2 decades, transgenic technology in mice has allowed for an unprecedented insight into the transcriptional control of reproductive development and function. The key factor among the mouse genetic tools that made this rapid advance possible is a conditional transgenic approach, a particularly versatile method of creating gene deletions and substitutions in the mouse genome. A centerpiece of this strategy is an enzyme, Cre recombinase, which is expressed from defined DNA regulatory elements that are active in the tissue of choice. The regulatory DNA element (either genetically engineered or natural) assures Cre expression only in predetermined cell types, leading to the guided deletion of genetically modified (flanked by loxP or 'floxed' by loxP) gene loci. This review summarizes and compares the studies in which genes encoding GATA family transcription factors were targeted either globally or by Cre recombinases active in the somatic cells of ovaries and testes. The conditional gene loss experiments require detailed knowledge of the spatial and temporal expression of Cre activity, and the challenges in interpreting the outcomes are highlighted. These studies also expose the complexity of GATA-dependent regulation of gonadal gene expression and suggest that gene function is highly context dependent.
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http://dx.doi.org/10.1530/REP-14-0086DOI Listing
July 2014

GATA4 autoregulates its own expression in mouse gonadal cells via its distal 1b promoter.

Biol Reprod 2014 Feb 6;90(2):25. Epub 2014 Feb 6.

Reproduction, Mother and Child Health, Centre de recherche du CHU de Québec and Centre de recherche en biologie de la reproduction (CRBR), Quebec City, Quebec, Canada.

Transcription factor GATA4 is required for the development and function of the mammalian gonads. We first reported that the GATA4 gene in both human and rodents is expressed as two major alternative transcripts that differ solely in their first untranslated exon (exon 1a vs. exon 1b). We had also showed by quantitative PCR that in mouse tissues, both Gata4 exon 1a- and 1b-containing transcripts are present in all sites that are normally positive for GATA4 protein. In adult tissues, exon 1a-containing transcripts generally predominate. A notable exception, however, is the testis where the Gata4 exon 1a and 1b transcripts exhibit a similar level of expression. We now confirm by in situ hybridization analysis that each transcript is also strongly expressed during gonad differentiation in both sexes in the rat. To gain further insights into how Gata4 gene expression is controlled, we characterized the mouse Gata4 promoter sequence located upstream of exon 1b. In vitro studies revealed that the Gata4 1b promoter is less active than the 1a promoter in several gonadal cell lines tested. Whereas we have previously shown that endogenous Gata4 transcription driven by the 1a promoter is dependent on a proximally located Ebox motif, we now show using complementary in vitro and in vivo approaches that Gata4 promoter 1b-directed expression is regulated by GATA4 itself. Thus, Gata4 transcription in the gonads and other tissues is ensured by distinct promoters that are regulated differentially and independently.
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http://dx.doi.org/10.1095/biolreprod.113.113290DOI Listing
February 2014

The transcription factor GATA4 is required for follicular development and normal ovarian function.

Dev Biol 2013 Sep 14;381(1):144-58. Epub 2013 Jun 14.

Department of Genetics, Dartmouth Medical School, Hanover, NH 03755, USA.

Sex determination in mammals requires interaction between the transcription factor GATA4 and its cofactor FOG2. We have recently described the function of both proteins in testis development beyond the sex determination stage; their roles in the postnatal ovary, however, remain to be defined. Here, we use gene targeting in mice to determine the requirement of GATA4 and FOG2 in ovarian development and folliculogenesis. The results from this study identify an essential role of the GATA4 protein in the ovarian morphogenetic program. We show that in contrast to the sex determination phase, which relies on the GATA4-FOG2 complex, the subsequent regulation of ovarian differentiation is dependent upon GATA4 but not FOG2. The loss of Gata4 expression within the ovary results in impaired granulosa cell proliferation and theca cell recruitment as well as fewer primordial follicles in the ovarian cortex, causing a failure in follicular development. Preantral follicular atresia is observed within the few follicles that develop despite Gata4 deficiency. The depletion of the follicular pool in GATA4 deficient ovary results in the formation of ovarian cysts and sterility.
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http://dx.doi.org/10.1016/j.ydbio.2013.06.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4089064PMC
September 2013

Ablation of the cardiac-specific gene leucine-rich repeat containing 10 (Lrrc10) results in dilated cardiomyopathy.

PLoS One 2012 7;7(12):e51621. Epub 2012 Dec 7.

Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.

Leucine-rich repeat containing 10 (LRRC10) is a cardiac-specific protein exclusively expressed in embryonic and adult cardiomyocytes. However, the role of LRRC10 in mammalian cardiac physiology remains unknown. To determine if LRRC10 is critical for cardiac function, Lrrc10-null (Lrrc10(-/-)) mice were analyzed. Lrrc10(-) (/-) mice exhibit prenatal systolic dysfunction and dilated cardiomyopathy in postnatal life. Importantly, Lrrc10(-/-) mice have diminished cardiac performance in utero, prior to ventricular dilation observed in young adults. We demonstrate that LRRC10 endogenously interacts with α-actinin and α-actin in the heart and all actin isoforms in vitro. Gene expression profiling of embryonic Lrrc10(-/-) hearts identified pathways and transcripts involved in regulation of the actin cytoskeleton to be significantly upregulated, implicating dysregulation of the actin cytoskeleton as an early defective molecular signal in the absence of LRRC10. In contrast, microarray analyses of adult Lrrc10(-/-) hearts identified upregulation of oxidative phosphorylation and cardiac muscle contraction pathways during the progression of dilated cardiomyopathy. Analyses of hypertrophic signal transduction pathways indicate increased active forms of Akt and PKCε in adult Lrrc10(-/-) hearts. Taken together, our data demonstrate that LRRC10 is essential for proper mammalian cardiac function. We identify Lrrc10 as a novel dilated cardiomyopathy candidate gene and the Lrrc10(-/-) mouse model as a unique system to investigate pediatric cardiomyopathy.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0051621PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3517560PMC
June 2013

GATA transcription factors in the developing reproductive system.

Adv Genet 2011 ;76:93-134

Department of Genetics, Dartmouth Medical School, Hanover, NH, USA.

Previous work has firmly established the role for both GATA4 and FOG2 in the initial global commitment to sexual fate, but their (joint or individual) function in subsequent steps remained unknown. Hence, gonad-specific deletions of these genes in mice were required to reveal their roles in sexual development and gene regulation. The development of tissue-specific Cre lines allowed for substantial advances in the understanding of the function of GATA proteins in sex determination, gonadal differentiation and reproductive development in mice. Here we summarize the recent work that examined the requirement of GATA4 and FOG2 proteins at several critical stages in testis and ovarian differentiation. We also discuss the molecular mechanisms involved in this regulation through the control of Dmrt1 gene expression in the testis and the canonical Wnt/ß-catenin pathway in the ovary.
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http://dx.doi.org/10.1016/B978-0-12-386481-9.00004-3DOI Listing
May 2012

Gone without the WNT: a requirement for WNT5A in germ cell migration and testis development.

Biol Reprod 2012 Jan 10;86(1):1-2. Epub 2012 Jan 10.

College of Veterinary Medicine, University of Florida, Gainesville, USA.

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http://dx.doi.org/10.1095/biolreprod.111.096461DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3313660PMC
January 2012

The fellowship of the ring.

Cancer Biol Ther 2011 Jan 1;11(1):48-9. Epub 2011 Jan 1.

Dartmouth Medical School, Norris Cotton Cancer Center, Hanover, NH, USA.

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http://dx.doi.org/10.4161/cbt.11.1.14042DOI Listing
January 2011

Cardiac expression of Tnnt1 requires the GATA4-FOG2 transcription complex.

ScientificWorldJournal 2009 Jul 4;9:575-87. Epub 2009 Jul 4.

Department of Genetics, Dartmouth Medical School, Hanover, NH, USA.

Previous work by us and others has shown that the loss of interaction between GATA4 and FOG2 protein partners is embryonic lethal due to heart failure at embryonic day (E) 13.5; however, the role of this important protein duo in various cardiac compartments (e.g., myocardial, endocardial, or epicardial cells) remains to be understood. Although a dual role (both as an activator and a repressor) for the GATA4-FOG2 transcriptional complex has been put forward, the specific genes under GATA4-FOG2 control in the developing heart have remained largely elusive. Since the myocardial-restricted Fog2 re-expression in the Fog2 null embryos is sufficient to extend their life span, identification of GATA4-FOG2 target genes in cardiomyocytes could shed light on the molecular mechanism of GATA4-FOG2 action in these cells. We report here that cardiac expression of slow skeletal troponin T (Tnnt1) strictly depends on the physical interaction between GATA4-FOG2 in the myocardium of both atria and ventricles.
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http://dx.doi.org/10.1100/tsw.2009.75DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5823129PMC
July 2009

Fog2 is critical for cardiac function and maintenance of coronary vasculature in the adult mouse heart.

J Clin Invest 2009 Jun;119(6):1462-76

Department of Cardiology, Children's Hospital Boston and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.

Aberrant transcriptional regulation contributes to the pathogenesis of both congenital and adult forms of heart disease. While the transcriptional regulator friend of Gata 2 (FOG2) is known to be essential for heart morphogenesis and coronary development, its tissue-specific function has not been previously investigated. Additionally, little is known about the role of FOG2 in the adult heart. Here we used spatiotemporally regulated inactivation of Fog2 to delineate its function in both the embryonic and adult mouse heart. Early cardiomyocyte- restricted loss of Fog2 recapitulated the cardiac and coronary defects of the Fog2 germline murine knockouts. Later cardiomyocyte-restricted loss of Fog2 (Fog2MC) did not result in defects in cardiac structure or coronary vessel formation. However, Fog2MC adult mice had severely depressed ventricular function and died at 8-14 weeks. Fog2MC adult hearts displayed a paucity of coronary vessels, associated with myocardial hypoxia, increased cardiomyocyte apoptosis, and cardiac fibrosis. Induced inactivation of Fog2 in the adult mouse heart resulted in similar phenotypes, as did ablation of the FOG2 interaction with the transcription factor GATA4. Loss of the FOG2 or FOG2-GATA4 interaction altered the expression of a panel of angiogenesis-related genes. Collectively, our data indicate that FOG2 regulates adult heart function and coronary angiogenesis.
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http://dx.doi.org/10.1172/JCI38723DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2689123PMC
June 2009

To beta or not to beta: canonical beta-catenin signaling pathway and ovarian development.

Dev Dyn 2008 Dec;237(12):3672-80

Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.

The mammalian embryonic gonad is a unique organ primordium in that it can adopt two different developmental fates-namely, differentiate as either a testis or an ovary-with dramatic consequences for an individual. While a molecular cascade culminating in testis development is well characterized, the ovarian pathways still remain enigmatic. The canonical Wnt/beta-catenin signaling implements a conserved mechanism of regulating gene expression that is integral to development of all metazoans. In this review, we summarize the recent evidence that suggests a central role for this signaling pathway in the development of the mammalian female.
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http://dx.doi.org/10.1002/dvdy.21784DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2837360PMC
December 2008

Ovarian development in mice requires the GATA4-FOG2 transcription complex.

Development 2008 Nov 16;135(22):3731-43. Epub 2008 Oct 16.

Department of Genetics, Dartmouth Medical School, Hanover, NH 03755, USA.

We have demonstrated previously that mammalian sexual differentiation requires both the GATA4 and FOG2 transcriptional regulators to assemble the functioning testis. Here we have determined that the sexual development of female mice is profoundly affected by the loss of GATA4-FOG2 interaction. We have also identified the Dkk1 gene, which encodes a secreted inhibitor of canonical beta-catenin signaling, as a target of GATA4-FOG2 repression in the developing ovary. The tissue-specific ablation of the beta-catenin gene in the gonads disrupts female development. In Gata4(ki/ki); Dkk1(-/-) or Fog2(-/-); Dkk1(-/-) embryos, the normal ovarian gene expression pattern is partially restored. Control of ovarian development by the GATA4-FOG2 complex presents a novel insight into the cross-talk between transcriptional regulation and extracellular signaling that occurs in ovarian development.
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http://dx.doi.org/10.1242/dev.024653DOI Listing
November 2008

GATA4/FOG2 transcriptional complex regulates Lhx9 gene expression in murine heart development.

BMC Dev Biol 2008 Jun 24;8:67. Epub 2008 Jun 24.

Department of Genetics, Dartmouth Medical School, Hanover, NH 03755, USA.

Background: GATA4 and FOG2 proteins are required for normal cardiac development in mice. It has been proposed that GATA4/FOG2 transcription complex exercises its function through gene activation as well as repression; however, targets of GATA4/FOG2 action in the heart remain elusive.

Results: Here we report identification of the Lhx9 gene as a direct target of the GATA4/FOG2 complex. We demonstrate that the developing mouse heart normally expresses truncated isoforms of Lhx9 - Lhx9alpha and Lhx9beta, and not the Lhx9-HD isoform that encodes a protein with an intact homeodomain. At E9.5 Lhx9alpha/beta expression is prominent in the epicardial primordium, septum transversum while Lhx9-HD is absent from this tissue; in the E11.5 heart LHX9alpha/beta-positive cells are restricted to the epicardial mesothelium. Thereafter in the control hearts Lhx9alpha/beta epicardial expression is promptly down-regulated; in contrast, mouse mutants with Fog2 gene loss fail to repress Lhx9alpha/beta expression. Chromatin immunoprecipitation from the E11.5 hearts demonstrated that Lhx9 is a direct target for GATA4 and FOG2. In transient transfection studies the expression driven by the cis-regulatory regions of Lhx9 was repressed by FOG2 in the presence of intact GATA4, but not the GATA4ki mutant that is impaired in its ability to bind FOG2.

Conclusion: In summary, the Lhx9 gene represents the first direct target of the GATA4/FOG2 repressor complex in cardiac development.
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http://dx.doi.org/10.1186/1471-213X-8-67DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2447832PMC
June 2008

The regulation of Sox9 gene expression by the GATA4/FOG2 transcriptional complex in dominant XX sex reversal mouse models.

Dev Biol 2007 Jul 3;307(2):356-67. Epub 2007 May 3.

Department of Genetics, Dartmouth Medical School, Hanover, NH, USA.

We have previously established an in vivo requirement for GATA4 and FOG2 transcription factors in sexual differentiation. Fog2 null mouse fetuses or fetuses homozygous for a targeted mutation in Gata4 (Gata4(ki)), which cripples the GATA4-FOG2 interaction, exhibit a profound and early block in testis differentiation in both sexes. Others have shown that XX mice with the Ods transgenic insertion or the Wt1-Sox9 YAC transgene overexpress the testis differentiation gene, Sox9. Thus, these XX animals undergo dominant sex reversal by developing into phenotypically normal, but sterile, males. Now we have determined that Fog2 haploinsufficiency prevents (suppresses) this dominant sex reversal and Fog2+/-Wt1-Sox9 or Ods XX animals develop normally--as fertile females. The suppression of sex reversal in Fog2 heterozygous females results from approximately 50% downregulation of the expression from the transgene-associated allele of Sox9. The GATA4/FOG2-dependent sex reversal observed in the transgenic XX gonads has to rely on gene targets other than the Y chromosome-linked Sry gene. Importantly, Fog2 null or Gata4(ki/ki) embryos (either XX or XY) fail to express detectable levels of Sox9 despite carrying the Ods mutation or Wt1-Sox9 transgene. Fog2 haploinsufficiency leads to a decreased amount of SOX9-positive cells in XY gonads. We conclude that FOG2 is a limiting factor in the formation of a functional GATA4/FOG2 transcription complex that is required for Sox9 expression during gonadogenesis.
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http://dx.doi.org/10.1016/j.ydbio.2007.04.040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2020840PMC
July 2007

GATA-4:FOG interactions regulate gastric epithelial development in the mouse.

Dev Dyn 2005 Oct;234(2):355-62

Department of Pediatrics, Washington University School of Medicine, St. Louis Children's Hospital, St. Louis, MO 63110, USA.

Transcription factor GATA-4 is a key participant in cytodifferentiation of the mouse hindstomach. Here we show that GATA-4 cooperates with a Friend-of-GATA (FOG) cofactor to direct gene expression in this segment of gut. Immunohistochemical staining revealed that GATA-4 and FOG-1 are co-expressed in hindstomach epithelial cells from embryonic days (E) 11.5 to 18.5. The other member of the mammalian FOG family, FOG-2, was not detected in gastric epithelium. To show that GATA-4:FOG interactions influence stomach development, we analyzed Gata4(ki/ki) mice, which express a mutant GATA-4 that cannot bind FOG cofactors. Sonic Hedgehog, an endoderm-derived signaling molecule normally down-regulated in the distal stomach, was over-expressed in hindstomach epithelium of E11.5 Gata4(ki/ki) mice, and there was a concomitant decrease in fibroblast growth factor-10 in adjacent mesenchyme. We conclude that functional interaction between GATA-4 and a member of the FOG family, presumably FOG-1, is required for proper epithelial-mesenchymal signaling in the developing stomach.
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http://dx.doi.org/10.1002/dvdy.20552DOI Listing
October 2005

Fog2 is required for normal diaphragm and lung development in mice and humans.

PLoS Genet 2005 Jul 17;1(1):58-65. Epub 2005 Jun 17.

Division of Emergency Medicine, Department of Medicine, Children's Hospital and Harvard Medical School, Boston, Massachusetts, USA.

Congenital diaphragmatic hernia and other congenital diaphragmatic defects are associated with significant mortality and morbidity in neonates; however, the molecular basis of these developmental anomalies is unknown. In an analysis of E18.5 embryos derived from mice treated with N-ethyl-N-nitrosourea, we identified a mutation that causes pulmonary hypoplasia and abnormal diaphragmatic development. Fog2 (Zfpm2) maps within the recombinant interval carrying the N-ethyl-N-nitrosourea-induced mutation, and DNA sequencing of Fog2 identified a mutation in a splice donor site that generates an abnormal transcript encoding a truncated protein. Human autopsy cases with diaphragmatic defect and pulmonary hypoplasia were evaluated for mutations in FOG2. Sequence analysis revealed a de novo mutation resulting in a premature stop codon in a child who died on the first day of life secondary to severe bilateral pulmonary hypoplasia and an abnormally muscularized diaphragm. Using a phenotype-driven approach, we have established that Fog2 is required for normal diaphragm and lung development, a role that has not been previously appreciated. FOG2 is the first gene implicated in the pathogenesis of nonsyndromic human congenital diaphragmatic defects, and its necessity for pulmonary development validates the hypothesis that neonates with congenital diaphragmatic hernia may also have primary pulmonary developmental abnormalities.
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http://dx.doi.org/10.1371/journal.pgen.0010010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1183529PMC
July 2005

Expression and regulation of mouse SERDIN1, a highly conserved cardiac-specific leucine-rich repeat protein.

Dev Dyn 2005 Jun;233(2):540-52

Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.

Despite recent progress, the precise mechanisms responsible for vertebrate cardiac development are still enigmatic. Better understanding of cardiac biology and disease necessitates identification and analysis of a full spectrum of regulatory and structural proteins specific to the developing heart. By performing an in silico screen, we identified a cardiac-specific gene we named Serdin1. The Serdin1 gene is conserved, and the message is restricted to the heart in several vertebrate species, thus implicating Serdin1 as an important gene in cardiac development. In situ hybridization confirmed that the Serdin1 message is cardiac-specific in mice as early as embryonic day 8.5. Antibody staining demonstrated predominantly nuclear staining in immortalized cardiac cell lines (P19 and HL-1) and proliferating cultured cardiomyocytes, whereas in vivo SERDIN1 localizes to I bands of the sarcomere. Seven kilobases of the upstream regulatory sequence of Serdin1 is sufficient for cardiac-specific expression. Computer analysis revealed an 80-bp homologous region between the mouse and the human Serdin genes that contains GATA, SRF, and MEF sites. Cardiac specificity and localization patterns suggest that SERDIN1 is intimately integrated with the molecular pathways controlling cardiogenesis in vertebrates.
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http://dx.doi.org/10.1002/dvdy.20368DOI Listing
June 2005

Developmental changes in ventricular diastolic function correlate with changes in ventricular myoarchitecture in normal mouse embryos.

Circ Res 2003 Oct 9;93(9):857-65. Epub 2003 Oct 9.

Cardiovascular Division, Beth Israel Deaconess Medical Center, Boston, Mass 02215, USA.

Both genetic and epigenetic factors, such as abnormal hemodynamics, affect cardiac morphogenesis and the pathogenesis of congenital heart disease. Diastolic function is an important determinant of cardiac function, and tools for evaluating diastolic function in the embryo would be very valuable for assessment of cardiac performance. Using histological measurements of ventricular myoarchitecture, Doppler assessment of ventricular inflow velocities, and direct measurement of ventricular pressure, we investigated developmental changes of ventricular diastolic function in the mouse embryos from embryonic days 9.5 to 19.5. Regression analysis showed that peak velocity of A wave (an index of passive compliance) correlated with the area of trabecular myocardium in right ventricle (RV) (r2=0.92, P<0.0001) and left ventricle (LV) (r2=0.93, P<0.0001). Peak velocity of E wave (an index of active relaxation) exponentially correlated with the area of compact myocardium in RV (r2=0.98, P<0.0001) and LV (r2=0.97, P<0.0001). We used these techniques to analyze FOG-2 null embryos. FOG-2 null embryos had thin compact myocardium, higher EDP and E/A ratio, smaller -dP/dt, and diminished sucking pressure than wild-type littermates, indicating that decreased ventricular diastolic function might be the primary cause of embryonic lethality. In conclusion, during embryogenesis the development of compact myocardium tightly regulates the development of ventricular distensibility. Our study in normal mice forms the basis for future studies of embryonic cardiac function in genetically manipulated mice with abnormalities of the cardiovascular system.
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http://dx.doi.org/10.1161/01.RES.0000100389.57520.1ADOI Listing
October 2003

Gonadal differentiation, sex determination and normal Sry expression in mice require direct interaction between transcription partners GATA4 and FOG2.

Development 2002 Oct;129(19):4627-34

Division of Hematology and Oncology, Children's Hospital, Harvard Medical School, Boston, MA, USA.

In mammals, Sry expression in the bipotential, undifferentiated gonad directs the support cell precursors to differentiate as Sertoli cells, thus initiating the testis differentiation pathway. In the absence of Sry, or if Sry is expressed at insufficient levels, the support cell precursors differentiate as granulosa cells, thus initiating the ovarian pathway. The molecular mechanisms upstream and downstream of Sry are not well understood. We demonstrate that the transcription factor GATA4 and its co-factor FOG2 are required for gonadal differentiation. Mouse fetuses homozygous for a null allele of Fog2 or homozygous for a targeted mutation in Gata4 (Gata4(ki)) that abrogates the interaction of GATA4 with FOG co-factors exhibit abnormalities in gonadogenesis. We found that Sry transcript levels were significantly reduced in XY Fog2(-/-) gonads at E11.5, which is the time when Sry expression normally reaches its peak. In addition, three genes crucial for normal Sertoli cell function (Sox9, Mis and Dhh) and three Leydig cell steroid biosynthetic enzymes (p450scc, 3betaHSD and p450c17) were not expressed in XY Fog2(-/-) and Gata(ki/ki) gonads, whereas Wnt4, a gene required for normal ovarian development, was expressed ectopically. By contrast, Wt1 and Sf1, which are expressed prior to Sry and necessary for gonad development in both sexes, were expressed normally in both types of mutant XY gonads. These results indicate that GATA4 and FOG2 and their physical interaction are required for normal gonadal development.
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October 2002