The human GATA-6 gene: structure, chromosomal location, and regulation of expression by tissue-specific and mitogen-responsive signals

Generation and characterization of GATA6-specific EGFP expressing human induced pluripotent stem cell line, KSCBi017-A-1, using CRISPR/Cas9

GATA6 is expressed during early embryogenesis and localizes to endoderm- and mesoderm-derived tissues during later embryogenesis. Here, we established a human induced pluripotent stem cell (hiPSC) line expressing EGFP under GATA6 gene. EGFP coding sequence was introduced into the C-terminus of GATA6 in KSCBi017-A hiPSCs through homologous recombination using CRISPR/Cas9 system. The successfully edited line, KSCBi017-A-1, was selected and confirmed by sequencing. The line had a normal karyotype and exhibited potential to differentiate into three germ layers while it expressed EGFP upon endoderm induction. KSCBi017-A-1 cells can be used to monitor the expression of GATA6 during differentiation. This cell line is available from Korea National Stem Cell Bank.

Clinical characteristics and genetic analysis of a child with specific type of diabetes mellitus caused by missense mutation of GATA6 gene

A 2-year-old boy was admitted to Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine in Nov 30th, 2018, due to polydipsia, polyphagia, polyuria accompanied with increased glucose levels for more than 2 weeks. He presented with symmetrical short stature [height 81 cm (－2.2 SD), weight 9.8 kg (－2.1 SD), body mass index 14.94 kg/m2 (P10-P15)], and with no special facial or physical features. Laboratory results showed that the glycated hemoglobin A1c was 14%, the fasting C-peptide was 0.3 ng/mL, and the islet autoantibodies were all negative. Oral glucose tolerance test showed significant increases in both fasting and postprandial glucose, but partial islet functions remained (post-load C-peptide increased 1.43 times compared to baseline). A heterozygous variant c.1366C>T (p.R456C) was detected in GATA6 gene, thereby the boy was diagnosed with a specific type of diabetes mellitus. The boy had congenital heart disease and suffered from transient hyperosmolar hyperglycemia after a patent ductus arteriosus surgery at 11 months of age. Insulin replacement therapy was prescribed, but without regular follow-up thereafter. The latest follow-up was about 3.5 years after the diagnosis of diabetes when the child was 5 years and 11 months old, with the fasting blood glucose of 6.0-10.0 mmol/L, and the 2 h postprandial glucose of 17.0-20.0 mmol/L.

BCL11B expression in hepatocellular carcinoma relates to chemosensitivity and clinical prognosis

INTRODUCTION

B-cell lymphoma/leukemia 11B (BCL11B) is a subunit of SWI/SNF chromatin remodeling complexes and functions in cell cycle regulation and apoptosis upon DNA replication stress and damages via transcription. Many malignancies were reported to exhibit changes in BCL11B gene expression; however, no study has focused on the relationship between BCL11B and hepatocellular carcinoma, which potentially exhibits DNA replication stress and damages upon its oncogenesis. Thus, in this study, we examined the molecular characterization of BCL11B expression in hepatocellular carcinoma.

METHODS AND RESULTS

The cumulative progression-free survival and overall survival were significantly longer in the clinical cases of BCL11B-negative hepatocellular carcinoma than BCL11B-positve cases. Microarray and real-time PCR analyses in hepatocellular carcinoma cell lines indicated a correlation between BCL11B and GATA6, a gene reported to be correlated with oncogenic activities and resistance to anthracycline, which is often used for hepatocellular carcinoma chemotherapy. Consequently, BCL11B-overexpressing cell lines exhibited resistance to anthracycline in cell growth assays and the resistance has been evidenced by the increased expression of BCL-xL in cell lines. The results were supported by the analyses of human HCC samples showing the correlation between BCL11B and GATA6 expressions.

DISCUSSIONS AND CONCLUSION

Our results indicated that overexpression of BCL11B amplifies GATA6 expression in hepatocellular carcinoma in vitro and in vivo that leads to anti-apoptotic signal activation, and induces resistance to chemotherapy, which influenced the postoperative prognosis.

GATA6 coordinates cross-talk between BMP10 and oxidative stress axis in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening condition characterized by a progressive increase in pulmonary vascular resistance leading to right ventricular failure and often death. Here we report that deficiency of transcription factor GATA6 is a shared pathological feature of PA endothelial (PAEC) and smooth muscle cells (PASMC) in human PAH and experimental PH, which is responsible for maintenance of hyper-proliferative cellular phenotypes, pulmonary vascular remodeling and pulmonary hypertension. We further show that GATA6 acts as a transcription factor and direct positive regulator of anti-oxidant enzymes, and its deficiency in PAH/PH pulmonary vascular cells induces oxidative stress and mitochondrial dysfunction. We demonstrate that GATA6 is regulated by the BMP10/BMP receptors axis and its loss in PAECs and PASMC in PAH supports BMPR deficiency. In addition, we have established that GATA6-deficient PAEC, acting in a paracrine manner, increase proliferation and induce other pathological changes in PASMC, supporting the importance of GATA6 in pulmonary vascular cell communication. Treatment with dimethyl fumarate resolved oxidative stress and BMPR deficiency, reversed hemodynamic changes caused by endothelial Gata6 loss in mice, and inhibited proliferation and induced apoptosis in human PAH PASMC, strongly suggesting that targeting GATA6 deficiency may provide a therapeutic advance for patients with PAH.

MicroRNAs, Stem Cells in Bipolar Disorder, and Lithium Therapeutic Approach

Bipolar disorder (BD) is a severe, chronic, and disabling neuropsychiatric disorder characterized by recurrent mood disturbances (mania/hypomania and depression, with or without mixed features) and a constellation of cognitive, psychomotor, autonomic, and endocrine abnormalities. The etiology of BD is multifactorial, including both biological and epigenetic factors. Recently, microRNAs (miRNAs), a class of epigenetic regulators of gene expression playing a central role in brain development and plasticity, have been related to several neuropsychiatric disorders, including BD. Moreover, an alteration in the number/distribution and differentiation potential of neural stem cells has also been described, significantly affecting brain homeostasis and neuroplasticity. This review aimed to evaluate the most reliable scientific evidence on miRNAs as biomarkers for the diagnosis of BD and assess their implications in response to mood stabilizers, such as lithium. Neural stem cell distribution, regulation, and dysfunction in the etiology of BD are also dissected.

Low Levels of MicroRNA-10a in Cardiovascular Endothelium and Blood Serum Are Related to Human Atherosclerotic Disease

Background

MicroRNA-10a (miR-10a) inhibits transcriptional factor GATA6 to repress inflammatory GATA6/VCAM-1 signaling, which is regulated by blood flow to affect endothelial function/dysfunction. This study aimed to identify the expression patterns of miR-10a/GATA6/VCAM-1 in vivo and study their implications in the pathophysiology of human coronary artery disease (CAD), i.e., atherosclerosis.

Methods

Human atherosclerotic coronary arteries and nondiseased arteries were used to detect the expressions of miR-10a/GATA6/VCAM-1 in pathogenic vs. normal conditions. In addition, sera from CAD patients and healthy subjects were collected to detect the level of circulating miR-10a.

Results

The comparison of human atherosclerotic coronary arteries with nondiseased arteries demonstrated that lower levels of endothelial miR-10a are related to human atherogenesis. Moreover, GATA6/VCAM-1 (a downstream target of miR-10a) was highly expressed in the endothelium, accompanied by the reduced levels of miR-10a during the development of human atherosclerosis. In addition, CAD patients had a significantly lower concentration of miR-10a in their serum compared to healthy subjects.

Conclusions

Our findings suggest that low miR-10a and high GATA6/VCAM-1 in the cardiovascular endothelium correlates to the development of human atherosclerotic lesions, suggesting that miR-10a signaling has the potential to be developed as a biomarker for human atherosclerosis.

Endothelial cells response to neutrophil-derived extracellular vesicles miRNAs in anti-PR3 positive vasculitis

In vasculitis disorders, inflammation affects blood vessels. Granulomatosis with polyangiitis (GPA) is a chronic systemic vasculitis distinguished by the presence of anti-proteinase-3 autoantibodies (anti-PR3). In this study we analyzed the molecular signature of human umbilical endothelial cells (HUVECs) in response to neutrophil-derived extracellular vesicles (EVs). EVs were obtained from anti-PR3-activated neutrophils, purified and characterized by flow cytometry, nanoparticle tracking and miRNA screening. HUVECs were stimulated with EVs and miRNA/mRNA expression was measured. Cell culture media proteins were identified by antibody microarrays and selected cytokines were measured. Comparison of differentially expressed miRNAs/mRNAs between non-stimulated and EV-stimulated HUVECs revealed two regulatory patterns. Significant up-regulation of 14 mRNA transcripts (including CXCL8, DKK1, IL1RL1, ANGPT-2, THBS1 and VCAM-1) was accompanied by 11 miRNAs silencing (including miR-661, miR-664a-3p, miR-377-3p, miR-30d-5p). Significant down-regulation was observed for nine mRNA transcripts (including FASLG, CASP8, STAT3, GATA3, IRAK1 and IL6) and accompanied by up-regulation of 10 miRNAs (including miR-223-3p, miR-142-3p, miR-211-5p). Stimulated HUVECs released IL-8, Dickkopf-related protein 1 (DKK-1), soluble interleukin (IL)-1 like receptor-1 (ST2), growth differentiation factor 15 (GDF-15), angiopoietin-2, endoglin, thrombospondin-1 and vascular adhesion molecule-1 (VCAM-1). Moreover, transfection of HUVECs with mimics of highly expressed in EVs miR-223-3p or miR-142-3p, stimulated production of IL-8, ST2 and endoglin. Cytokines released by HUVECs were also elevated in blood of patients with GPA. The most increased were IL-8, DKK-1, ST2, angiopoietin-2 and IL-33. In-vitro stimulation of HUVECs by neutrophil-derived EVs recapitulates contribution of endothelium in autoimmune vasculitis. Proinflammatory phenotype of released cytokines corresponds with the regulatory network of miRNAs/mRNAs comprising both EVs miRNA and endothelial cell transcripts.

GATA binding protein 6 (GATA6) is co-amplified with PIK3CA in patients with esophageal adenocarcinoma and is linked to neoadjuvant therapy

Purpose

Driver mutations are typically absent in esophageal adenocarcinoma (EAC). Mostly, oncogenes are amplified as driving molecular events (including GATA6-amplification in 14% of cases). However, only little is known about its biological function and clinical relevance.

Methods

We examined a large number of EAC (n = 496) for their GATA6 amplification by fluorescence in situ hybridization (FISH) analyzing both primary resected (n = 219) and neoadjuvant treated EAC (n = 277). Results were correlated to clinicopathological data and known mutations/amplifications in our EAC-cohort.

Results

GATA6 amplification was detectable in 49 (9.9%) EACs of our cohort. We observed an enrichment of GATA6-positive tumors among patients after neoadjuvant treatment (12,3% amplified tumors versus 6,8% in the primary resected group; p = 0.044). Additionally, there was a simultaneous amplification of PIK3CA and GATA6 (p < 0.001) not detectable when analyzing other genes such as EGFR, ERBB2, KRAS or MDM2. Although we did not identify a survival difference depending on GATA6 in the entire cohort (p = 0.212), GATA6 amplification was associated with prolonged overall survival among patients with primary surgery (median overall-survival 121.1 vs. 41.4 months, p = 0.032). Multivariate cox-regression analysis did not confirm GATA6 as an independent prognostic marker, neither in the entire cohort (p = 0.210), nor in the subgroup with (p = 0.655) or without pretreatment (p = 0.961).

Conclusions

Our study investigates the relevance of GATA6 amplification on a large tumor collective, which includes primary resected tumors and the clinically relevant group of neoadjuvant treated EACs. Especially in the pretreated group, we found an accumulation of GATA6-amplified tumors (12.3%) and a frequent co-amplification of PIK3CA. Our data suggest an increased resistance to radio-chemotherapy in GATA6-amplified tumors.

A Novel STAT3-Mediated GATA6 Pathway Contributes to tert-Butylhydroquinone- (tBHQ-) Protected TNFα-Activated Vascular Cell Adhesion Molecule 1 (VCAM-1) in Vascular Endothelium

The activation of vascular cell adhesion molecule 1 (VCAM-1) in vascular endothelial cells has been well considered implicating in the initiation and processing of atherosclerosis. Oxidative stress is mechanistically involved in proatherosclerotic cytokine-induced VCAM-1 activation. tert-Butylhydroquinone (tBHQ), a synthetic phenolic antioxidant used for preventing lipid peroxidation of food, possesses strongly antioxidant capacity against oxidative stress-induced dysfunction in various pathological process. Here, we investigated the protective role of tBHQ on tumor necrosis factor alpha- (TNFα-) induced VCAM-1 activation in both aortic endothelium of mice and cultured human vascular endothelial cells and uncovered its potential mechanisms. Our data showed that tBHQ treatment significantly reversed TNFα-induced activation of VCAM-1 at both transcriptional and protein levels. The mechanistic study revealed that inhibiting neither nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nor autophagy blocked the beneficial role of tBHQ. Alternatively, tBHQ intervention markedly alleviated TNFα-increased GATA-binding protein 6 (GATA6) mRNA and protein expressions and its translocation into nucleus. Further investigation indicated that tBHQ-inhibited signal transducer and activator of transcription 3 (STAT3) but not mitogen-activated protein kinase (MAPK) pathway contributed to its protective role against VCAM-1 activation via regulating GATA6. Collectively, our data demonstrated that tBHQ prevented TNFα-activated VCAM-1 via a novel STAT3/GATA6-involved pathway. tBHQ could be a potential candidate for the prevention of proatherosclerotic cytokine-caused inflammatory response and further dysfunctions in vascular endothelium.

Cell-Specific Effects of GATA (GATA Zinc Finger Transcription Factor Family)-6 in Vascular Smooth Muscle and Endothelial Cells on Vascular Injury Neointimal Formation

Objective- Transcription factor GATA (GATA zinc finger transcription factor family)-6 is highly expressed in vessels and rapidly downregulated in balloon-injured carotid arteries and viral delivery of GATA-6 to the vessels limited the neointimal formation, however, little is known about its cell-specific regulation of in vivo vascular smooth muscle cell (VSMC) phenotypic state contributing to neointimal formation. This study aims to determine the role of vascular cell-specific GATA-6 in ligation- or injury-induced neointimal hyperplasia in vivo. Approach and Results- Endothelial cell and VSMC-specific GATA-6 deletion mice are generated, and the results indicate that endothelial cell-specific GATA-6 deletion mice exhibit significant decrease of VSMC proliferation and attenuation of neointimal formation after artery ligation and injury compared with the wild-type littermate control mice. PDGF (platelet-derived growth factor)-B is identified as a direct target gene, and endothelial cell-GATA-6-PDGF-B pathway regulates VSMC proliferation and migration in a paracrine manner which controls the neointimal formation. In contrast, VSMC-specific GATA-6 deletion promotes injury-induced VSMC transformation from contractile to proliferative synthetic phenotype leading to increased neointimal formation. CCN (cysteine-rich 61/connective tissue growth factor/nephroblastoma overexpressed family)-5 is identified as a novel target gene, and VSMC-specific CCN-5 overexpression in mice reverses the VSMC-GATA-6 deletion-mediated increased cell proliferation and migration and finally attenuates the neointimal formation. Conclusions- This study gives us a direct in vivo evidence of GATA-6 cell lineage-specific regulation of PDGF-B and CCN-5 on VSMC phenotypic state, proliferation and migration contributing to neointimal formation, which advances our understanding of in vivo neointimal hyperplasia, meanwhile also provides opportunities for future therapeutic interventions.

TCF7L2 (Transcription Factor 7-Like 2) Regulation of GATA6 (GATA-Binding Protein 6)-Dependent and -Independent Vascular Smooth Muscle Cell Plasticity and Intimal Hyperplasia

Supplemental Digital Content is available in the text.

Objective—

TCF7L2 (transcription factor 7-like 2) is a Wnt-regulated transcription factor that maintains stemness and promotes proliferation in embryonic tissues and adult stem cells. Mice with a coronary artery disease–linked mutation in Wnt-coreceptor LRP6 (LDL receptor-related protein 6) exhibit vascular smooth muscle cell dedifferentiation and obstructive coronary artery disease, which are paradoxically associated with reduced TCF7L2 expression. We conducted a comprehensive study to explore the role of TCF7L2 in vascular smooth muscle cell differentiation and protection against intimal hyperplasia.

Approach and Results—

Using multiple mouse models, we demonstrate here that TCF7L2 promotes differentiation and inhibits proliferation of vascular smooth muscle cells. TCF7L2 accomplishes these effects by stabilization of GATA6 (GATA-binding protein 6) and upregulation of SM-MHC (smooth muscle cell myosin heavy chain) and cell cycle inhibitors. Accordingly, TCF7L2 haploinsufficient mice exhibited increased susceptibility to injury-induced hyperplasia, while mice overexpressing TCF7L2 were protected against injury-induced intimal hyperplasia compared with wild-type littermates. Consequently, the overexpression of TCF7L2 in LRP6 mutant mice rescued the injury-induced intimal hyperplasia.

Conclusions—

Our novel findings imply cell type-specific functional role of TCF7L2 and provide critical insight into mechanisms underlying the pathogenesis of intimal hyperplasia.

Genetic and Functional Variants Analysis of the GATA6 Gene Promoter in Acute Myocardial Infarction

Background: Acute myocardial infarction (AMI) which is a specific type of coronary artery disease (CAD), is caused by the combination of genetic factors and acquired environment. Although some common genetic variations have been recorded to contribute to the development of CAD and AMI, more genetic factors and potential molecular mechanisms remain largely unknown. The GATA6 gene is expressed in the heart during embryogenesis and is also detected in vascular smooth muscle cells (VSMCs), different human primary endothelial cells (ECs), and vascular ECs in mice. To date, no studies have directly linked GATA6 gene with regulation of the CAD.

Methods: In this study, we used a case-control study to investigate and analyze the genetic variations and functional variations of the GATA6 gene promoter region in AMI patients and controls. A variety of statistical analysis methods were utilized to analyze the association of single nucleotide polymorphisms (SNPs) with AMI. Functional analysis of DNA sequence variants (DSVs) was performed using a dual luciferase reporter assay. In vitro, electrophoretic mobility shift assay (EMSA) was selected to examine DNA-protein interactions.

Results: A total of 705 subjects were enrolled in the study. Ten DSVs were found in AMI patients (n = 352) and controls (n = 353), including seven SNPs. One novel heterozygous DSV, (g.22168409 A > G), and two SNPs, [g.22168362 C > A(rs1416421760) and g.22168521 G > T(rs1445501474)], were reported in three AMI patients, which were not found in controls. The relevant statistical analysis, including allele and genotype frequencies between AMI patients and controls, five genetic models, linkage disequilibrium (LD) and haplotype analysis, and SNP–SNP interactions, suggested no statistical significance (P > 0.05). The transcriptional activity of GATA6 gene promoter was significantly increased by the DSV (g.22168409 A > G) and SNP [g.22168362 C > A(rs1416421760)]. The EMSA revealed that the DSV (g.22168409 A > G) and SNP [g.22168362 C > A(rs1416421760)] evidently influenced the binding of transcription factors.

Conclusion: In conclusion, the DSV (g.22168409 A > G) and SNP [g.22168362 C > A(rs1416421760)] may increase GATA6 levels in both HEK-293 and H9c2 cell lines by affecting the binding of transcription factors. Whether the two variants identified in the GATA6 gene promoter can promote the development and progression of human AMI by altering GATA6 levels still requires further studies to verify.

Multiple roles and regulatory mechanisms of the transcription factor GATA6 in human cancers

Cancer is a common type of non-communicable disease, and its morbidity and mortality are rapidly increasing. It is expected to become the largest obstacle to the promotion of global human health in the future. Some transcription factors that play important regulatory roles in embryogenesis and subsequent tissue maintenance can be selectively amplified during tumorigenesis. Due to its high expression in the embryonic endoderm and mesoderm, GATA6 plays a crucial role in the normal development of early human heart, lung, digestive system, adrenal glands, breasts, ovaries, retina, skin, and nervous system. Up to now, overexpression of the GATA6 gene has been shown to play an important role in several cancers, including lung cancer, digestive system tumors, breast cancer, and ovarian cancer. However, the human body is a complex organism, which causes the transcription factor GATA6 to have multiple roles in cancer. In this review, we summarize the multiple roles of transcription factor GATA6 in various cancers and its regulatory mechanisms. The aim is to better understand the relationship between GATA6 gene expression and cancer development and to provide new insights for exploring potential therapeutic targets.

GATA6 loss-of-function mutations contribute to familial dilated cardiomyopathy

Dilated cardiomyopathy (DCM), the most prevalent form of primary heart muscle disease, is the third most common cause of heart failure and the most frequent reason for cardiac transplantation. Mounting evidence has demonstrated that genetic risk factors are crucial in the pathogenesis of DCM. However, DCM is genetically heterogeneous, and the genetic basis of DCM in a large majority of cases remains unclear. In the current study, the coding exons and flanking introns of the GATA6 gene, which encodes a zinc‑finger transcription factor essential for cardiogenesis, was sequenced in 140 unrelated patients with DCM, and two novel heterozygous mutations, p.C447Y and p.H475R, were identified in two index patients with DCM, respectively. Analysis of the pedigrees showed that in each family the mutation co-segregated with DCM transmitted in an autosomal-dominant pattern, with complete penetrance. The missense mutations were absent in 400 control chromosomes and predicted to be disease-causing by MutationTaster or probably damaging by PolyPhen-2. The alignment of multiple GATA6 proteins across species revealed that the altered amino acids were completely conserved evolutionarily. The functional assays showed that the mutated GATA6 proteins were associated with significantly reduced transcriptional activation in comparison with their wild-type counterpart. To the best of our knowledge, this is the first study on the association of GATA6 loss-of-function mutations with enhanced susceptibility to familial DCM, which provides novel insight into the molecular mechanism of DCM and suggests potential implications for the antenatal prophylaxis and allele-specific treatment of DCM.

Novel and functional DNA sequence variants within the GATA6 gene promoter in ventricular septal defects

Congenital heart disease (CHD) is the most common birth defect in humans. Genetic causes and underlying molecular mechanisms for isolated CHD remain largely unknown. Studies have demonstrated that GATA transcription factor 6 (GATA6) plays an essential role in the heart development. Mutations in GATA6 gene have been associated with diverse types of CHD. As GATA6 functions in a dosage-dependent manner, we speculated that changed GATA6 levels, resulting from DNA sequence variants (DSVs) within the gene regulatory regions, may mediate the CHD development. In the present study, GATA6 gene promoter was genetically and functionally analyzed in large groups of patients with ventricular septal defect (VSD) (n = 359) and ethnic-matched healthy controls (n = 365). In total, 11 DSVs, including four SNPs, were identified in VSD patients and controls. Two novel and heterozygous DSVs, g.22169190A>T and g.22169311C>G, were identified in two VSD patients, but in none of controls. In cultured cardiomyocytes, the activities of the GATA6 gene promoter were significantly reduced by the DSVs g.22169190A>T and g.22169311C>G. Therefore, our findings suggested that the DSVs within the GATA6 gene promoter identified in VSD patients may change GATA6 levels, contributing to the VSD development as a risk factor.

Two functional sequence variants of the GATA6 gene promoter in patients with indirect inguinal hernia

Inguinal hernia is a common surgical disease, majority of which are indirect inguinal hernia (IIH). A positive family history has indicated that genetic factors play important roles in the IIH development. To date, genetic causes and underlying mechanisms for inguinal hernia remain largely unknown. During the embryonic development, GATA transcription factor 6 (GATA6) plays an essential role. Mutations in GATA6 gene and changed GATA6 levels have been associated with human diseases. As GATA6 acts in a dosage-dependent manner, we speculated that changed GATA6 levels, resulting from DNA sequence variants (DSVs) within the gene regulatory regions, may mediate the IIH development. In this study, the GATA6 gene promoter was genetically and functionally analyzed in IIH patients and ethnic-matched controls. Eleven DNA sequence variants (DSVs), including four SNPs and seven new variants, within the GATA6 gene promoter were identified. Two heterozygous DSVs, g.22168361C>A and g.22169106C>T, were identified in two IIH patients, but in none of controls. In cultured human fibroblast, these DSVs significantly reduced the GATA6 gene promoter activities. In addition, three heterozygous DSVs were only found in three controls. Five DSVs, including four SNPs and one new variant, were found in both IIH patients and controls with similar frequencies. Therefore, the DSVs within the GATA6 gene promoter may contribute to the IIH development as a risk factor by changing the GATA6 levels.

Mechanism of the susceptibility of remodeled pulmonary vessels to drug-induced cell killing

Background

Pulmonary arterial hypertension remains a devastating disease without a cure. The major complication of this disease is the abnormal growth of vascular cells, resulting in pulmonary vascular remodeling. Thus, agents, which affect the remodeled vessels by killing unwanted cells, should improve treatment strategies. The present study reports that antitumor drugs selectively kill vascular cells in remodeled pulmonary vessels in rat models of pulmonary hypertension.

Methods and Results

After developing pulmonary vascular remodeling in chronic hypoxia or chronic hypoxia/SU‐5416 models, rats were injected with antitumor drugs including proteasome inhibitors (bortezomib and MG‐132) and daunorubicin. Within 1 to 3 days, these agents reduced the media and intima thickness of remodeled pulmonary vascular walls, but not the thickness of normal pulmonary vessels. These drugs also promoted apoptotic and autophagic death of vascular cells in the remodeled vessels, but not in normal vessels. We provide evidence that the upregulation of annexin A1, leading to GATA4‐dependent downregulation of Bcl‐x_L, is a mechanism for specific apoptotic killing, and for the role of parkin in defining specificity of autophagic killing of remodeled vascular cells. The reversal of pulmonary vascular remodeling increased the capacity of vasodilators to reduce pulmonary arterial pressure.

Conclusions

These results suggest that antitumor drugs can specifically kill cells in remodeled pulmonary vascular walls and may be useful for improving the efficacy of current therapeutic strategies to treat pulmonary arterial hypertension.

Multiple nuclear localization signals mediate nuclear localization of the GATA transcription factor AreA

The Aspergillus nidulans GATA transcription factor AreA activates transcription of nitrogen metabolic genes in response to nitrogen limitation and is known to accumulate in the nucleus during nitrogen starvation. Sequence analysis of AreA revealed multiple nuclear localization signals (NLSs), five putative classical NLSs conserved in fungal AreA orthologs but not in the Saccharomyces cerevisiae functional orthologs Gln3p and Gat1p, and one putative noncanonical RRX33RXR bipartite NLS within the DNA-binding domain. In order to identify the functional NLSs in AreA, we constructed areA mutants with mutations in individual putative NLSs or combinations of putative NLSs and strains expressing green fluorescent protein (GFP)-AreA NLS fusion genes. Deletion of all five classical NLSs individually or collectively did not affect utilization of nitrogen sources or AreA-dependent gene expression and did not prevent AreA nuclear localization. Mutation of the bipartite NLS conferred the inability to utilize alternative nitrogen sources and abolished AreA-dependent gene expression likely due to effects on DNA binding but did not prevent AreA nuclear localization. Mutation of all six NLSs simultaneously prevented AreA nuclear accumulation. The bipartite NLS alone strongly directed GFP to the nucleus, whereas the classical NLSs collaborated to direct GFP to the nucleus. Therefore, AreA contains multiple conserved NLSs, which show redundancy and together function to mediate nuclear import. The noncanonical bipartite NLS is conserved in GATA factors from Aspergillus, yeast, and mammals, indicating an ancient origin.

Transcription factors GATA-4 and GATA-6: molecular characterization, expression patterns and possible functions during goose (Anser cygnoides) follicle development

The transcription factors GATA-4 and GATA-6, members of the GATA family, play an important role in ovarian cell proliferation, differentiation and apoptosis. In this study, the full-length coding sequences of goose GATA-4 and GATA-6 were cloned and characterized. GATA-4 and GATA-6 consist of 1236 and 1104 nucleotides encoding proteins with 411 and 367 amino acids, respectively. The deduced amino acid sequences of both proteins include two adjacent zinc finger domains with the distinctive form (CVNC-X17-CNAC)-X29-(CANC-X17-CNAC) and share 84.76% identity within this domain. In silico prediction together with matching of the high affinity RRXS(T)Y motif revealed that the GATA-4 protein might be phosphorylated predominantly at S(233), but no phosphorylation site was found in the GATA-6 protein. Real-time quantitative PCR analysis showed that GATA-4 and GATA-6 mRNAs were co-expressed in goose follicles, moderately expressed in granulosa cells and weakly expressed in theca cells. The expression level of GATA-4 mRNA in healthy follicles was significantly higher than in atretic follicles or postovulatory follicles (P<0.01), and the expression level of GATA-6 mRNA in healthy follicles was significantly lower than in atretic follicles or postovulatory follicles (P<0.01). The expression level of GATA-4 mRNA in granulosa cells was downregulated during follicle development; the peak of expression occurred in the 8-10 mm follicles, and the lowest expression was in the F1 follicles. GATA-6 was upregulated and reached its peak expression in the F1 follicles. These results indicate that the molecular structural differences in goose GATA-4 and GATA-6 may be related to their different roles during follicle development.

Lessons from the heart: mirroring electrophysiological characteristics during cardiac development to in vitro differentiation of stem cell derived cardiomyocytes

The ability of human pluripotent stem cells (hPSCs) to differentiate into any cell type of the three germ layers makes them a very promising cell source for multiple purposes, including regenerative medicine, drug discovery, and as a model to study disease mechanisms and progression. One of the first specialized cell types to be generated from hPSC was cardiomyocytes (CM), and differentiation protocols have evolved over the years and now allow for robust and large-scale production of hPSC-CM. Still, scientists are struggling to achieve the same, mainly ventricular, phenotype of the hPSC-CM in vitro as their adult counterpart in vivo. In vitro generated cardiomyocytes are generally described as fetal-like rather than adult. In this review, we compare the in vivo development of cardiomyocytes to the in vitro differentiation of hPSC into CM with focus on electrophysiology, structure and contractility. Furthermore, known epigenetic changes underlying the differences between adult human CM and CM differentiated from pluripotent stem cells are described. This should provide the reader with an extensive overview of the current status of human stem cell-derived cardiomyocyte phenotype and function. Additionally, the reader will gain insight into the underlying signaling pathways and mechanisms responsible for cardiomyocyte development.

Gata6 is required for complete acinar differentiation and maintenance of the exocrine pancreas in adult mice

OBJECTIVES

Previous studies have suggested an important role of the transcription factor Gata6 in endocrine pancreas, while GATA6 haploinsufficient inactivating mutations cause pancreatic agenesis in humans. We aimed to analyse the effects of Gata6 inactivation on pancreas development and function.

DESIGN

We deleted Gata6 in all epithelial cells in the murine pancreas at the onset of its development. Acinar proliferation, apoptosis, differentiation and exocrine functions were assessed using reverse transcriptase quantitative PCR (RT-qPCR), chromatin immunoprecipitation, immunohistochemistry and enzyme assays. Adipocyte transdifferentiation was assessed using electron microscopy and genetic lineage tracing.

RESULTS

Gata6 is expressed in all epithelial cells in the adult mouse pancreas but it is only essential for exocrine pancreas homeostasis: while dispensable for pancreatic development after e10.5, it is required for complete acinar differentiation, for establishment of polarity and for the maintenance of acinar cells in the adult. Gata6 regulates directly the promoter of genes coding for digestive enzymes and the transcription factors Rbpjl and Mist1. Upon pancreas-selective Gata6 inactivation, massive loss of acinar cells and fat replacement take place. This is accompanied by increased acinar apoptosis and proliferation, acinar-to-ductal metaplasia and adipocyte transdifferentiation. By contrast, the endocrine pancreas is spared.

CONCLUSIONS

Our data show that Gata6 is required for the complete differentiation of acinar cells through multiple transcriptional regulatory mechanisms. In addition, it is required for the maintenance of the adult acinar cell compartment. Our studies suggest that GATA6 alterations may contribute to diseases of the human adult exocrine pancreas.

GATA-2 transduces LPS-induced il-1β gene expression in macrophages via a toll-like receptor 4/MD88/MAPK-dependent mechanism

Lipopolysaccharide (LPS) is a critical factor for inducing acute lung injury. GATA-2, a transcription factor, contributes to the control of cell activity and function. Exposure of RAW 264.7 cells to LPS induced interleukin (IL)-1β mRNA and protein expression and GATA-2 translocation from the cytoplasm to nuclei in concentration- and time-dependent manners. A bioinformatic search revealed that GATA-2-specific binding elements exist in the 5’-promoter region of the il-1β gene. LPS could enhance the transactivation activity of GATA-2 in macrophages. Knocking-down translation of GATA-2 mRNA using RNA interference significantly alleviated LPS-induced IL-1β mRNA and protein expression. As to the mechanism, transfection of toll-like receptor (TLR) 4 small interfering (si)RNA into macrophages concurrently decreased LPS-caused increases in nuclear GATA-2 levels. Sequentially, treatment with myeloid differentiation factor 88 (MyD88) siRNA decreased LPS-induced phosphorylation of mitogen-activated protein kinases (MAPKs) kinase 1/2 and subsequent translocation of GATA-2. Reducing MAPK activities using specific inhibitors simultaneously decreased GATA-2 activation. Furthermore, exposure of primary macrophages to LPS significantly increased the transactivation activities of GATA-2 and IL-1β mRNA and protein expression. Transfection of GATA-2 siRNA inhibited LPS-induced IL-1β mRNA expression. Results of this study show that LPS induction of il-1β gene expression in macrophages is mediated by GATA-2 via activation of TLR4, MyD88, and MAPKs.

Endothelial GATA-6 deficiency promotes pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic and progressive disease characterized by pulmonary vasculopathy with elevation of pulmonary artery pressure, often culminating in right ventricular failure. GATA-6, a member of the GATA family of zinc-finger transcription factors, is highly expressed in quiescent vasculature and is frequently lost during vascular injury. We hypothesized that endothelial GATA-6 may play a critical role in the molecular mechanisms underlying endothelial cell (EC) dysfunction in PAH. Here we report that GATA-6 is markedly reduced in pulmonary ECs lining both occluded and nonoccluded vessels in patients with idiopathic and systemic sclerosis-associated PAH. GATA-6 transcripts are also rapidly decreased in rodent PAH models. Endothelial GATA-6 is a direct transcriptional regulator of genes controlling vascular tone [endothelin-1, endothelin-1 receptor type A, and endothelial nitric oxide synthase (eNOS)], pro-inflammatory genes, CX3CL1 (fractalkine), 5-lipoxygenease-activating protein, and markers of vascular remodeling, including PAI-1 and RhoB. Mice with the genetic deletion of GATA-6 in ECs (Gata6-KO) spontaneously develop elevated pulmonary artery pressure and increased vessel muscularization, and these features are further exacerbated in response to hypoxia. Furthermore, innate immune cells including macrophages (CD11b(+)/F4/80(+)), granulocytes (Ly6G(+)/CD45(+)), and dendritic cells (CD11b(+)/CD11c(+)) are significantly increased in normoxic Gata6-KO mice. Together, our findings suggest a critical role of endothelial GATA-6 deficiency in development and disease progression in PAH.

Somatic mutations in the GATA6 gene underlie sporadic tetralogy of Fallot

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease associated with significant morbidity and mortality in humans. However, the molecular etiology underlying TOF in most patients remains largely unknown. In the present study, sequence analysis of the GATA6 gene was performed from fresh-frozen cardiac tissues and matched blood samples of 52 unrelated patients who underwent surgical repair of TOF. The cardiac tissues and matched blood specimens from 46 patients who underwent cardiac valve replacement due to rheumatic heart disease and blood samples from 200 healthy individuals as controls were genotyped. The functional characteristics of the mutations were assessed using a luciferase reporter assay system. Based on the results, two novel heterozygous GATA6 mutations, p.G367X and p.G394C, were identified in the cardiac tissues of 2 TOF patients, respectively. No mutations were found in the cardiac tissues from 46 patients with rheumatic heart disease and in the blood samples from the 298 participants. Functional analysis demonstrated that the GATA6 mutants were consistently associated with significantly reduced transcriptional activation compared with their wild-type counterpart. This is the first report on the link of somatic GATA6 mutation to TOF, providing novel insight into the molecular mechanism involved in TOF.

Novel GATA6 mutations associated with congenital ventricular septal defect or tetralogy of fallot

Congenital heart disease (CHD) is the most common form of developmental malformation and is the leading noninfectious cause of infant mortality. Emerging evidence indicates that genetic defects are involved in the pathogenesis of CHD. Nevertheless, CHD is genetically heterogeneous, and the molecular basis for CHD in a majority of patients remains unknown. In this study, the whole coding region of GATA6, a gene encoding a zinc-finger transcription factor crucial for normal cardiogenesis, was sequenced in 380 unrelated patients with CHD. The relatives of the index patients harboring the identified mutations and 200 unrelated control individuals were subsequently genotyped. The functional effect of the mutations was characterized using a luciferase reporter assay system. As a result, two novel heterozygous GATA6 mutations, p.D404Y and p.E460X, were identified in two families with ventricular septal defect and tetralogy of Fallot, respectively. The mutations co-segregated with CHD in the families with complete penetrance, and were absent in 400 control chromosomes. Functional analysis demonstrated that the mutated GATA6 proteins were associated with significantly decreased transactivational activity in comparison with their wild-type counterpart. These findings provide novel insight into the molecular mechanism implicated in CHD, suggesting potential implications for the early prophylaxis and personalized treatment of CHD.

Novel GATA6 loss-of-function mutation responsible for familial atrial fibrillation

Atrial fibrillation (AF) is the most commonly sustained cardiac arrhythmia, and confers a substantially increased risk of morbidity and mortality. Increasing evidence has indicated that hereditary defects are implicated in AF. However, AF is genetically heterogeneous and the genetic etiology of AF in a significant portion of patients remains unclear. In this study, the entire coding sequence and splice junctions of the GATA6 gene, which encodes a zinc-finger transcription factor crucial for cardiogenesis, were sequenced in 140 unrelated patients with lone AF. The available relatives of the index patient carrying an identified mutation and 200 unrelated ethnically-matched healthy individuals used as the controls were genotyped. The functional characteristics of the mutant GATA6 were assessed in contrast to its wild-type counterpart using a luciferase reporter assay system. As a result, a novel heterozygous GATA6 mutation, p.G469V, was identified in a family with AF inherited in an autosomal dominant pattern. The mutation was absent in the 200 control individuals and the altered amino acid was completely conserved across species. Functional analysis demonstrated that the GATA6 mutation was associated with a significantly decreased transcriptional activity. The findings provide novel insight into the molecular mechanism involved in the pathogenesis of AF, as well as insight into potential therapies for the prevention and treatment of AF.

GATA6 loss-of-function mutation in atrial fibrillation

Atrial fibrillation (AF) is the most common type of sustained cardiac arrhythmia and is associated with substantial morbidity and mortality. Increasing evidence demonstrates that hereditary defects are involved in the pathogenesis of AF. However, AF is of remarkable genetic heterogeneity, and the heritable components responsible for AF in the majority of patients remain unclear. In this study, the entire coding region of the GATA6 gene, which encodes a zinc-finger transcription factor crucial for cardiogenesis, was sequenced in 138 unrelated patients with lone AF, and a novel heterozygous GATA6 mutation, c.704A > C equivalent to p.Y235S, was identified in a patient. The detected substitution, which altered the amino acid highly conserved evolutionarily across species, was absent in 200 unrelated ethnically matched healthy individuals, and was predicted to be disease-causing by MutationTaster. Genetic analysis of the available relatives of the mutation carrier showed that in the family the variation co-segregated with the disease transmitted as an autosomal dominant trait, with complete penetrance. The functional analysis performed using a luciferase reporter assay system revealed that the mutant GATA6 protein resulted in significantly decreased transcriptional activity compared with its wild-type counterpart. These findings provide novel insight into the molecular pathophysiology implicated in AF, suggesting the potential implications in the prophylactic strategy and effective therapy for this common arrhythmia.

A genome-wide analysis of open chromatin in human tracheal epithelial cells reveals novel candidate regulatory elements for lung function

BACKGROUND

Distal cell-type-specific regulatory elements may be located at very large distances from the genes that they control and are often hidden within intergenic regions or in introns of other genes. The development of methods that enable mapping of regions of open chromatin genome wide has greatly advanced the identification and characterisation of these elements.

METHODS

Here we use DNase I hypersensitivity mapping followed by deep sequencing (DNase-seq) to generate a map of open chromatin in primary human tracheal epithelial (HTE) cells and use bioinformatic approaches to characterise the distribution of these sites within the genome and with respect to gene promoters, intronic and intergenic regions.

RESULTS

Genes with HTE-selective open chromatin at their promoters were associated with multiple pathways of epithelial function and differentiation. The data predict novel cell-type-specific regulatory elements for genes involved in HTE cell function, such as structural proteins and ion channels, and the transcription factors that may interact with them to control gene expression. Moreover, the map of open chromatin can identify the location of potentially critical regulatory elements in genome-wide association studies (GWAS) in which the strongest association is with single nucleotide polymorphisms in non-coding regions of the genome. We demonstrate its relevance to a recent GWAS that identifies modifiers of cystic fibrosis lung disease severity.

CONCLUSION

Since HTE cells have many functional similarities with bronchial epithelial cells and other differentiated cells in the respiratory epithelium, these data are of direct relevance to elucidating the molecular basis of normal lung function and lung disease.

Human embryonic stem cells express elevated levels of multiple pro-apoptotic BCL-2 family members

Two of the greatest challenges in regenerative medicine today remain (1) the ability to culture human embryonic stem cells (hESCs) at a scale sufficient to satisfy clinical demand and (2) the ability to eliminate teratoma-forming cells from preparations of cells with clinically desirable phenotypes. Understanding the pathways governing apoptosis in hESCs may provide a means to address these issues. Limiting apoptosis could aid scaling efforts, whereas triggering selective apoptosis in hESCs could eliminate unwanted teratoma-forming cells. We focus here on the BCL-2 family of proteins, which regulate mitochondrial-dependent apoptosis. We used quantitative PCR to compare the steady-state expression profile of all human BCL-2 family members in hESCs with that of human primary cells from various origins and two cancer lines. Our findings indicate that hESCs express elevated levels of the pro-apoptotic BH3-only BCL-2 family members NOXA, BIK, BIM, BMF and PUMA when compared with differentiated cells and cancer cells. However, compensatory expression of pro-survival BCL-2 family members in hESCs was not observed, suggesting a possible explanation for the elevated rates of apoptosis observed in proliferating hESC cultures, as well as a mechanism that could be exploited to limit hESC-derived neoplasms.

Sphingosine 1-phosphate induces differentiation of mesoangioblasts towards smooth muscle. A role for GATA6

Different cells can contribute to repair following vascular injury by differentiating into smooth muscle (SM) cells; however the extracellular signals involved are presently poorly characterized. Mesoangioblasts are progenitor cells capable of differentiating into various mesoderm cell types including SM cells. In this study the biological action exerted by the pleiotropic sphingolipid sphingosine 1-phosphate (S1P) in human mesoangioblasts has been initially investigated by cDNA microarray analysis. Obtained data confirmed the anti-apoptotic action of this sphingolipid and identified for the first time a strong differentiating action toward SM cells. Quantitative mRNA and protein analysis corroborated the microarray results demonstrating enhanced expression of myogenic marker proteins and regulation of the expression of transcription factor GATA6 and its co-regulator, LMCD1. Importantly, GATA6 up-regulation induced by S1P was responsible for the enhanced expression of SM-specific contractile proteins. Moreover, by specific gene silencing experiments GATA6 was critical in the pro-differentiating activity of the cytokine TGFβ. Finally, the pharmacological inhibition of endogenous S1P formation in response to TGFβ abrogated GATA6 up-regulation, supporting the view that the S1P pathway plays a physiological role in mediating the pro-myogenic effect of TGFβ. This study individuates GATA6 as novel player in the complex transcriptional regulation of mesoangioblast differentiation into SM cells and highlights a role for S1P to favour vascular regeneration.

Beta-catenin signaling in hepatic development and progenitors: which way does the WNT blow?

The Wnt/β-catenin pathway is an evolutionarily conserved signaling cascade that plays key roles in development and adult tissue homeostasis and is aberrantly activated in many tumors. Over a decade of work in mouse, chick, xenopus, and zebrafish models has uncovered multiple functions of this pathway in hepatic pathophysiology. Specifically, beta-catenin, the central component of the canonical Wnt pathway, is implicated in the regulation of liver regeneration, development, and carcinogenesis. Wnt-independent activation of beta-catenin by receptor tyrosine kinases has also been observed in the liver. In liver development across various species, through regulation of cell proliferation, differentiation, and maturation, beta-catenin directs foregut endoderm specification, hepatic specification of the foregut, and hepatic morphogenesis. Its role has also been defined in adult hepatic progenitors or oval cells especially in their expansion and differentiation. Thus, beta-catenin undergoes tight temporal regulation to exhibit pleiotropic effects during hepatic development and in hepatic progenitor biology.

GATA-3 transduces survival signals in osteoblasts through upregulation of bcl-x(L) gene expression

GATA-3, a transcription factor, participates in regulating cell development, proliferation, and death. This study was aimed at evaluating the roles of GATA-3 in protecting osteoblasts against oxidative stress-induced apoptotic insults and their possible mechanisms. Pretreatment with nitric oxide (NO) for 24 hours protected osteoblasts, prepared from neonatal rat calvaria, against oxidative stress-induced apoptotic insults. Such protection involved enhancement of Bcl-X(L) messenger mRNA and protein syntheses and the translocation of this antiapoptotic protein from the cytoplasm to mitochondria. GATA-3 was detected in rat osteoblasts, and GATA-3-specific DNA-binding elements exist in the promoter region of the bcl-x(L) gene. NO preconditioning attenuated oxidative stress-caused suppression of GATA-3 mRNA and protein synthesis and the translocation of this transcription factor from the cytoplasm to nuclei. Application of GATA-3 small interfering siRNA into osteoblasts decreased the levels of this transcription factor and simultaneously inhibited Bcl-X(L) mRNA synthesis. Pretreatment with NO lowered the oxidative stress-caused alteration in the binding of GATA-3 to its specific DNA motifs. Oxidative stress-inhibited Runx2 mRNA expression, but NO preconditioning decreased such inhibition. NO pretreatment time-dependently enhanced the association of GATA-3 with Runx2. Knocking down the translation of GATA-3 using RNA interference significantly decreased the protection of NO preconditioning against oxidative stress-induced alterations of cell morphologies, DNA fragmentation, and cell apoptosis. In comparison, overexpression of GATA-3 could promote NO preconditioning-involved Bcl-X(L) expression and cell survival. Therefore, this study shows that GATA-3 plays critical roles in mediating survival signals in osteoblasts, possibly through upregulating bcl-x(L) gene expression.

Simvastatin restores down-regulated GATA-6 expression in pulmonary hypertensive rats

Vascular smooth muscle cell proliferation has been known to be predominant in vascular remodeling of pulmonary hypertensive. The GATA family proteins, a group of zinc finger transcription factors, play an important role during cell proliferation. The aim of present study was to investigate the expression of GATA-6 gene in experimental pulmonary hypertensive rats and explore the effect of regulation of GATA-6 expression by simvastatin on pulmonary vascular remodeling. The male Sprague-Dawley rats model was established with receiving pneumonectomy and monocrotaline (MCT) administration. Right pulmonary artery remodeling in these animals was compared with untreated rats or rats receiving simvastatin. The level of GATA-6 mRNA and protein expression was detected by reverse transcriptase–polymerase chain reaction (RT-PCR) and Western blotting, respectively. Pneumonectomized, MCT-treated rats had significantly increased mean pulmonary arterial pressure (mPAP), RV/(LV + S) ratio (ratio of the right ventricular to left ventricular and septum weights), vascular occlusion scores (VOSs), and percent media wall thickness on day 35, all the indices were significantly decreased after simvastatin administration in these rats. The level of GATA-6 mRNA and protein were markedly decreased in these pneumonectomy and MCT-treated rats, and they were significantly up-regulated in these rats after receiving simvastatin. These results indicate that the development and progression of pulmonary hypertension is prevented by simvastatin by up-regulating GATA-6 expression in the lung tissue.

Oncogenic Ras upregulates NADPH oxidase 1 gene expression through MEK-ERK-dependent phosphorylation of GATA-6

Ras oncogene upregulates the expression of nicotinamide adenine dinucleotide phosphate oxidase (Nox) 1 via the Raf/MEK/ERK pathway, leading to the elevated production of reactive oxygen species that is essential for maintenance of Ras-transformation phenotypes. However, the precise transcriptional control mechanism underlying Ras-induced Nox1 expression remains to be elucidated. Here we demonstrated that via the MEK/ERK pathway, Ras signaling enhances the activity of the functional Nox1 promoter (nt -321 to -1) in colon cancer CaCo-2 cells and thereby induces the formation of the specific protein-DNA complexes in the two GATA-binding site-containing regions (nt -161 to -136 and -125 to -100). Supershift assays with GATA antibodies, protein analyses and chromatin immunoprecipitation revealed that GATA-6 is a component of the specific protein-DNA complexes at the Nox1 promoter. GATA-6 was able to trans-activate the Nox1 promoter but not a promoter in which the GATA-binding sites are mutated. Moreover, GATA-6 was phosphorylated at serine residues by MEK-activated ERK, which increased GATA-6 DNA binding, correlating with suppression of the Nox1 promoter activity by an MEK inhibitor PD98059. Finally, the site-directed mutation of the consensus ERK phosphorylation site (PYS(120)P to PYA(120)P) of GATA-6 abolished its trans-activation activity, suppressing of the growth of CaCo-2 cells. On the basis of these results, we propose that oncogenic Ras signaling upregulates the transcription of Nox1 through MEK-ERK-dependent phosphorylation of GATA-6.

Hepatocyte nuclear factor 4alpha contributes to thyroid hormone homeostasis by cooperatively regulating the type 1 iodothyronine deiodinase gene with GATA4 and Kruppel-like transcription factor 9

Type 1 iodothyronine deiodinase (Dio1), a selenoenzyme catalyzing the bioactivation of thyroid hormone, is highly expressed in the liver. Dio1 mRNA and enzyme activity levels are markedly reduced in the livers of hepatocyte nuclear factor 4alpha (HNF4alpha)-null mice, thus accounting for its liver-specific expression. Consistent with this deficiency, serum T4 and rT3 concentrations are elevated in these mice compared with those in HNF4alpha-floxed control littermates; however, serum T3 levels are unchanged. Promoter analysis of the mouse Dio1 gene demonstrated that HNF4alpha plays a key role in the transactivation of the mouse Dio1 gene. Deletion and substitution mutation analyses demonstrated that a proximal HNF4alpha site (direct repeat 1 [TGGACAAAGGTGC]; HNF4alpha-RE) is crucial for transactivation of the mouse Dio1 gene by HNF4alpha. Mouse Dio1 is also stimulated by thyroid hormone signaling, but a direct role for thyroid hormone receptor action has not been reported. We also showed that thyroid hormone-inducible Krüppel-like factor 9 (KLF9) stimulates the mouse Dio1 promoter very efficiently through two CACCC sequences that are located on either side of HNF4alpha-RE. Furthermore, KLF9 functions together with HNF4alpha and GATA4 to synergistically activate the mouse Dio1 promoter, suggesting that Dio1 is regulated by thyroid hormone in the mouse through an indirect mechanism requiring prior KLF9 induction. In addition, we showed that physical interactions between the C-terminal zinc finger domain (Cf) of GATA4 and activation function 2 of HNF4alpha and between the basic domain adjacent to Cf of GATA4 and a C-terminal domain of KLF9 are both required for this synergistic response. Taken together, these results suggest that HNF4alpha regulates thyroid hormone homeostasis through transcriptional regulation of the mouse Dio1 gene with GATA4 and KLF9.

Identification of p300-targeted acetylated residues in GATA4 during hypertrophic responses in cardiac myocytes

A zinc finger protein, GATA4, is one of the hypertrophy-responsive transcription factors and increases its DNA binding and transcriptional activities in response to hypertrophic stimuli in cardiac myocytes. Activation of GATA4 during this process is mediated, in part, through acetylation by intrinsic histone acetyltransferases such as a transcriptional coactivator p300. However, p300-targeted acetylated sites of GATA4 during myocardial cell hypertrophy have not been identified. By mutational analysis, we showed that 4 lysine residues located between amino acids 311 and 322 are required for synergistic activation of atrial natriuretic factor and endothelin-1 promoters by GATA4 and p300. A tetra-mutant GATA4, in which these 4 lysine residues were simultaneously mutated, retained the ability to localize in nuclei and to interact with cofactors including FOG-2, GATA6, and p300 but lacked p300-induced acetylation, DNA binding, and transcriptional activities. Furthermore, coexpression of the tetra-mutant GATA4 with wild-type GATA4 impaired the p300-induced acetylation, DNA binding, and transcriptional activities of the wild type. When we expressed the tetra-mutant GATA4 in neonatal rat cardiac myocytes using a lentivirus vector, this mutant suppressed phenylephrine-induced increases in cell size, protein synthesis, and expression of hypertrophy-responsive genes. However, its expression did not affect the basal state. Thus, we have identified the most critical lysine residues acting as p300-mediated acetylation targets in GATA4 during hypertrophic responses in cardiac myocytes. The results also demonstrate that GATA4 with simultaneous mutation of these sites specifically suppresses hypertrophic responses as a dominant-negative form, providing further evidence for the acetylation of GATA4 as one of critical nuclear events in myocardial cell hypertrophy.

Role of the GATA family of transcription factors in endocrine development, function, and disease

The WGATAR motif is a common nucleotide sequence found in the transcriptional regulatory regions of numerous genes. In vertebrates, these motifs are bound by one of six factors (GATA1 to GATA6) that constitute the GATA family of transcriptional regulatory proteins. Although originally considered for their roles in hematopoietic cells and the heart, GATA factors are now known to be expressed in a wide variety of tissues where they act as critical regulators of cell-specific gene expression. This includes multiple endocrine organs such as the pituitary, pancreas, adrenals, and especially the gonads. Insights into the functional roles played by GATA factors in adult organ systems have been hampered by the early embryonic lethality associated with the different Gata-null mice. This is now being overcome with the generation of tissue-specific knockout models and other knockdown strategies. These approaches, together with the increasing number of human GATA-related pathologies have greatly broadened the scope of GATA-dependent genes and, importantly, have shown that GATA action is not necessarily limited to early development. This has been particularly evident in endocrine organs where GATA factors appear to contribute to the transcription of multiple hormone-encoding genes. This review provides an overview of the GATA family of transcription factors as they relate to endocrine function and disease.

GATA-6 is a novel transcriptional repressor of the human Tenascin-C gene expression in fibroblasts

In this study we show that GATA-6 is a novel repressor of TN-C gene expression. We demonstrated that overexpression of GATA-6 in fibroblasts inhibited basal levels, as well as markedly decreased IL-4- and TGF-beta-induced TN-C mRNA and protein levels. A GATA-6 response element was mapped to position -467 to -460 of the TN-C promoter. In addition, we showed that GATA-6 binds this site both in vitro and in vivo.

Cooperative interaction between hepatocyte nuclear factor 4 alpha and GATA transcription factors regulates ATP-binding cassette sterol transporters ABCG5 and ABCG8

Cholesterol homeostasis is maintained by coordinate regulation of cholesterol synthesis and its conversion to bile acids in the liver. The excretion of cholesterol from liver and intestine is regulated by ATP-binding cassette half-transporters ABCG5 and ABCG8. The genes for these two proteins are closely linked and divergently transcribed from a common intergenic promoter region. Here, we identified a binding site for hepatocyte nuclear factor 4alpha (HNF4alpha) in the ABCG5/ABCG8 intergenic promoter, through which HNF4alpha strongly activated the expression of a reporter gene in both directions. The HNF4alpha-responsive element is flanked by two conserved GATA boxes that were also required for stimulation by HNF4alpha. GATA4 and GATA6 bind to the GATA boxes, coexpression of GATA4 and HNF4alpha leads to a striking synergistic activation of both the ABCG5 and the ABCG8 promoters, and binding sites for HNF4alpha and GATA were essential for maximal synergism. We also show that HNF4alpha, GATA4, and GATA6 colocalize in the nuclei of HepG2 cells and that a physical interaction between HNF4alpha and GATA4 is critical for the synergistic response. This is the first demonstration that HNF4alpha acts synergistically with GATA factors to activate gene expression in a bidirectional fashion.

The human cumulus--oocyte complex gene-expression profile

BACKGROUND

The understanding of the mechanisms regulating human oocyte maturation is still rudimentary. We have identified transcripts differentially expressed between immature and mature oocytes and cumulus cells.

METHODS

Using oligonucleotide microarrays, genome-wide gene expression was studied in pooled immature and mature oocytes or cumulus cells from patients who underwent IVF.

RESULTS

In addition to known genes, such as DAZL, BMP15 or GDF9, oocytes up-regulated 1514 genes. We show that PTTG3 and AURKC are respectively the securin and the Aurora kinase preferentially expressed during oocyte meiosis. Strikingly, oocytes overexpressed previously unreported growth factors such as TNFSF13/APRIL, FGF9, FGF14 and IL4 and transcription factors including OTX2, SOX15 and SOX30. Conversely, cumulus cells, in addition to known genes such as LHCGR or BMPR2, overexpressed cell-to-cell signalling genes including TNFSF11/RANKL, numerous complement components, semaphorins (SEMA3A, SEMA6A and SEMA6D) and CD genes such as CD200. We also identified 52 genes progressively increasing during oocyte maturation, including CDC25A and SOCS7.

CONCLUSION

The identification of genes that were up- and down-regulated during oocyte maturation greatly improves our understanding of oocyte biology and will provide new markers that signal viable and competent oocytes. Furthermore, genes found expressed in cumulus cells are potential markers of granulosa cell tumours.