Mouse GATA-4: a retinoic acid-inducible GATA-binding transcription factor expressed in endodermally derived tissues and heart

Regulation of hepatocyte nuclear factor 4 alpha-mediated transcription

Hepatocyte nuclear factor 4alpha (HNF4alpha, NR2A1) is required for development of the liver and for controlling the expression of many genes specifically expressed in the liver and associated with a number of critical metabolic pathways. Among the genes regulated by HNF4alpha are the xenobiotic-metabolizing cytochromes P450, UDP-glucuronosyltransferases and sulfotransferases thus making this transcription factor critical in the control of drug metabolism. HNF4alpha, a member of the nuclear receptor superfamily, binds as a homodimer to direct repeat elements upstream of target genes. However, in contrast to many other nuclear receptors, there is no convincing evidence that HNF4alpha is activated by exogenous ligands, at least in the classic mechanism used by other steroid and metabolic nuclear receptors. X-ray crystallographic studies revealed that HNF4alpha has a fatty acid embedded in its putative ligand binding site that may not be easily released or displaced by exogenous ligands. HNF4alpha, as a general rule, controls constitutive expression of many hepatic genes but under certain circumstances can be subjected to regulation by differential co-activator recruitment, by phosphorylation and by interaction with other nuclear receptors. The ability of HNF4alpha to be regulated offers hope that it could be a drug target.

Maternal cocaine administration in mice alters DNA methylation and gene expression in hippocampal neurons of neonatal and prepubertal offspring

Previous studies documented significant behavioral changes in the offspring of cocaine-exposed mothers. We now explore the hypothesis that maternal cocaine exposure could alter the fetal epigenetic machinery sufficiently to cause lasting neurochemical and functional changes in the offspring. Pregnant CD1 mice were administered either saline or 20 mg/kg cocaine twice daily on gestational days 8–19. Male pups from each of ten litters of the cocaine and control groups were analyzed at 3 (P3) or 30 (P30) days postnatum. Global DNA methylation, methylated DNA immunoprecipitation followed by CGI² microarray profiling and bisulfite sequencing, as well as quantitative real-time RT-PCR gene expression analysis, were evaluated in hippocampal pyramidal neurons excised by laser capture microdissection. Following maternal cocaine exposure, global DNA methylation was significantly decreased at P3 and increased at P30. Among the 492 CGIs whose methylation was significantly altered by cocaine at P3, 34% were hypermethylated while 66% were hypomethylated. Several of these CGIs contained promoter regions for genes implicated in crucial cellular functions. Endogenous expression of selected genes linked to the abnormally methylated CGIs was correspondingly decreased or increased by as much as 4–19-fold. By P30, some of the cocaine-associated effects at P3 endured, reversed to opposite directions, or disappeared. Further, additional sets of abnormally methylated targets emerged at P30 that were not observed at P3. Taken together, these observations indicate that maternal cocaine exposure during the second and third trimesters of gestation could produce potentially profound structural and functional modifications in the epigenomic programs of neonatal and prepubertal mice.

Ventral closure, headfold fusion and definitive endoderm migration defects in mouse embryos lacking the fibronectin leucine-rich transmembrane protein FLRT3

The three fibronectin leucine-rich repeat transmembrane (FLRT) proteins contain 10 leucine-rich repeats (LRR), a type III fibronectin (FN) domain, followed by the transmembrane region, and a short cytoplasmic tail. XFLRT3, a Nodal/TGFbeta target, regulates cell adhesion and modulates FGF signalling during Xenopus gastrulation. The present study describes the onset and pattern of FLRT1-3 expression in the early mouse embryo. FLRT3 expression is activated in the anterior visceral endoderm (AVE), and during gastrulation appears in anterior streak derivatives namely the node, notochord and the emerging definitive endoderm. To explore FLRT3 function we generated a null allele via gene targeting. Early Nodal activities required for anterior-posterior (A-P) patterning, primitive streak formation and left-right (L-R) axis determination were unperturbed. However, FLRT3 mutant embryos display defects in headfold fusion, definitive endoderm migration and a failure of the lateral edges of the ventral body wall to fuse, leading to cardia bifida. Surprisingly, the mutation has no effect on FGF signalling. Collectively these experiments demonstrate that FLRT3 plays a key role in controlling cell adhesion and tissue morphogenesis in the developing mouse embryo.

Islet1 cardiovascular progenitors: a single source for heart lineages?

The creation of regenerative stem cell therapies for heart disease requires that we understand the molecular mechanisms that govern the fates and differentiation of the diverse muscle and non-muscle cell lineages of the heart. Recently, different cardiac cell types have been reported to arise from a common, multipotent Islet1 (Isl1)-positive progenitor, suggesting that a clonal model of heart lineage diversification might occur that is analogous to hematopoiesis. The ability to isolate, renew and differentiate Isl1(+) precursors from postnatal and embryonic hearts and from embryonic stem cells provides a powerful cell-based system for characterizing the signaling pathways that control cardiovascular progenitor formation, renewal, lineage specification and conversion to specific differentiated progeny.

Gene expression in the developing diaphragm: significance for congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a frequently occurring birth defect and a source of potentially fatal neonatal respiratory distress. Recently, through the application of detailed karyotyping methods, several CDH-critical regions within the human genome have been identified. These regions typically contain several genes. Here we focused on genes from 15q26, the best-characterized CDH-critical region, as well as FOG2 and GATA4, genes singled out from CDH-critical regions at 8q22-8q23 and 8p23.1, respectively. We tested the hypothesis that these putative CDH-related genes are expressed within the developing diaphragm at the time of the hypothesized initial defect. Our results show that 15q26 contains a cluster of genes that are expressed in the developing rodent diaphragm, consistent with an association between deletions in this region and CDH. We then examined the protein expression pattern of positively identified genes within the developing diaphragm. Two major themes emerged. First, those factors strongly associated with CDH are expressed only in the nonmuscular, mesenchymal component of the diaphragm, supporting the hypothesis that CDH has its origins in a mesenchymal defect. Second, these factors are all coexpressed in the same cells. This suggests that cases of CDH with unique genetic etiology may lead to a common defect in these cells and supports the hypothesis that these factors may be members of a common pathway. This study is the first to provide a detailed examination of how genes associated with CDH are expressed in the developing diaphragm and provides an important foundation for understanding how the deletion of specific genes may contribute to abnormal diaphragm formation.

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.

Characterization of embryoid bodies of mouse embryonic stem cells formed under various culture conditions and estimation of differentiation status of such bodies

Various types of embryoid body (EB) that were formed from mouse embryonic stem (ES) cells under various culture conditions were characterized in terms of gene expression pattern to estimate the differentiation status of the bodies. The gene expression of typical markers (i.e., GATA-4, GATA-6, transthyretin [TTR], alpha-fetoprotein [AFP], Nkx2.5, and alpha-myosin heavy chain [alpha-MHC]) was quantitatively analyzed in various types of EB, and the gene expression pattern of those marker genes was graphically shown for each EB. The gene expression pattern accurately represented the differentiation status of the EBs. The gene expression pattern indicated that the Nkx2.5 and alpha-MHC genes were highly expressed in the EBs formed from 1000 ES cells in a low-adherence 96-well plate. By transferring the EBs into an attachment culture, cardiomyocytes were more efficiently generated in the outgrowth of the EBs. When we increased the seeding cell number from 1000 to 4000 ES cells, the gene expression pattern changed, that is, the expression levels of the TTR and AFP genes increased, whereas those of the Nkx2.5 and alpha-MHC genes decreased, and the trend of differentiation changed from cardiomyogenesis to visceral yolk-sac-like structure formation.

Generation of Multipotential Mesendodermal Progenitors from Mouse Embryonic Stem Cells via Sustained Wnt Pathway Activation

Pluripotent embryonic stem cells (ESCs) are capable of differentiating into cell types belonging to all three germ layers within the body, which makes them an interesting and intense field of research. Inefficient specific differentiation and contamination with unwanted cell types are the major issues in the use of ESCs in regenerative medicine. Lineage-specific progenitors generated from ESCs could be utilized to circumvent the issue. We demonstrate here that sustained activation of the Wnt pathway (using Wnt3A or an inhibitor of glycogen synthase kinase 3beta) in multiple mouse and human ESCs results in meso/endoderm-specific differentiation. Using monolayer culture conditions, we have generated multipotential "mesendodermal progenitor clones" (MPC) from mouse ESCs by sustained Wnt pathway activation. MPCs express increased levels of meso/endodermal and mesendodermal markers and exhibit a stable phenotype in culture over a year. The MPCs have enhanced potential to differentiate along endothelial, cardiac, vascular smooth muscle, and skeletal lineages than undifferentiated ESCs. In conclusion, we demonstrate that the Wnt pathway activation can be utilized to generate lineage-specific progenitors from ESCs, which can be further differentiated into desired organ-specific cells.

Cell autonomous sorting and surface positioning in the formation of primitive endoderm in embryoid bodies

The differentiation and formation of the primitive endoderm in early embryos can be mimicked in vitro by the aggregation of embryonic stem cells to form embryoid bodies. We present morphological evidence that primitive endoderm cells often first locate in the interior of embryoid bodies and subsequently migrate to the surface. Cell mixing experiments indicate that surface positioning is an intrinsic property of endoderm epithelial cells. Moreover, Disabled-2 (Dab2) is required for surface sorting and positioning of the endoderm cells: when Dab2 expression was eliminated, the differentiated endoderm epithelial cells distributed throughout the interior of the embryoid bodies. Surprisingly, E-cadherin is dispensable for primitive endoderm differentiation and surface sorting in embryoid bodies. These results support the model that primitive endoderm cells first emerge in the interior of the inner cell mass and are subsequently sorted to the surface to form the primitive endoderm.

Oct-4, Rex-1, and Gata-4 expression in human MSC increase the differentiation efficiency but not hTERT expression

Micro-environment seems to exert an important influence on human mesenchymal stem cell (MSC) differentiation and proliferative capacity in bone marrow as well as in culture ex vivo. Oct-4, Rex-1, and TERT genes are well-known for the maintenance of pluripotentiality differentiation and the proliferative capacity of embryonic stem cells. Some previous data report expression of these embryonic factors in selected clones from bone marrow adult stem cells. Our goal was to study expression of Oct-4, Rex-1, and TERT in primary cultured human MSC according to the serum concentration. In addition, we have studied the expression of Gata-4 since this factor plays a key role in organogenesis. We hypothesized that low serum concentration with appropriate growth factors may induce an undifferentiated status with a re-expression of embryonic factors and extend differentiation capacity. Thus, using a defined culture medium, we report on the increased expression of Oct-4, Rex-1, and Gata-4 in human MSC. We have correlated this expression to an increase in differentiation efficiency towards osteogenic and adipogenic phenotypes. Our data suggest that the culture medium used permits the emergence of adult stem cells with a high differentiation capacity and expression of embryonic factors. These cells may have important implications for cell therapy.

Cardiac BNP gene activation by angiotensin II in vivo

The transcription factors involved in the activation of cardiac gene expression by angiotensin II (Ang II) in vivo are not well understood. Here we studied the contribution of transcriptional elements to the activation of the cardiac B-type natriuretic peptide (BNP) gene promoter by Ang II in conscious rats and in angiotensin II type 1 receptor (AT1R) transgenic mice. Rat BNP luciferase reporter gene constructs were injected into the left ventricular wall. The mean luciferase activity was 1.8-fold higher (P<0.05) in the ventricles of animals subjected to 2-week Ang II infusion as compared with vehicle infusion. Our results indicate that GATA binding sites at -90 and -81 in the rat BNP promoter are essential for the in vivo response to Ang II. The GATA factor binding to these sites is GATA-4. BNP mRNA levels and GATA-4 binding activity are also increased in the hypertrophied hearts of aged AT1R transgenic mice.

Extra-embryonic endoderm cells derived from ES cells induced by GATA factors acquire the character of XEN cells

Background

Three types of cell lines have been established from mouse blastocysts: embryonic stem (ES) cells, trophoblast stem (TS) cells, and extra-embryonic endoderm (XEN) cells, which have the potential to differentiate into their respective cognate lineages. ES cells can differentiate in vitro not only into somatic cell lineages but into extra-embryonic lineages, including trophectoderm and extra-embryonic endoderm (ExEn) as well. TS cells can be established from ES cells by the artificial repression of Oct3/4 or the upregulation of Cdx2 in the presence of FGF4 on feeder cells. The relationship between these embryo-derived XEN cells and ES cell-derived ExEn cell lines remains unclear, although we have previously reported that overexpression of Gata4 or Gata6 induces differentiation of mouse ES cells into extra-embryonic endoderm in vitro.

Results

A system in which GATA factors were conditionally activated revealed that the cells continue to proliferate while expressing a set of extra-embryonic endoderm markers, and, following injection into blastocysts, contribute only to the extra-embryonic endoderm lineage in vivo. Although the in vivo contribution is limited to cells of parietal endoderm lineage, Gata-induced extra-embryonic endoderm cells (gExEn) can be induced to differentiate into visceral endoderm-like cells in vitro by repression of Gata6. During early passage, the propagation of gExEn cells is dependent on the expression of the Gata6 transgene. These cells, however, lose this dependency following establishment of endogenous Gata6 expression.

Conclusion

We show here that Gata-induced extra-embryonic endoderm cells derived from ES cells mimic the character of XEN cells. These findings indicate that Gata transcription factors are sufficient for the derivation and propagation of XEN-like extra-embryonic endoderm cells from ES cells.

Cooperation between GATA4 and TGF-beta signaling regulates intestinal epithelial gene expression

Members of the transforming growth factor-beta (TGF-beta) family have been shown to play an important role in the regulation of gut epithelial gene expression. We have used the intestinal alkaline phosphatase (IAP) and intestinal fatty acid binding protein (IFABP) promoters to dissect the mechanisms by which TGF-beta1 signaling regulates gut epithelial gene expression. TGF-beta signaling alone was not sufficient for activation of IAP and IFABP promoters. However, TGF-beta signaling cooperated with the gut epithelial transcription factor GATA4 to synergistically activate IAP and IFABP promoters. Coexpression of GATA4 along with the TGF-beta1 signal transducing downstream effectors such as Smad2, 3, and 4 resulted in synergistic activation of both IAP and IFABP promoters. This synergistic activation was reduced by simultaneous expression of dominant-negative Smad4. -40 and -89 GATA binding sites in the IFABP promoter were required for the synergistic activation by Smad2, 3, and 4 and GATA4. GATA4 and Smad2, 3, and 4 physically associated with each other and this interaction was mediated through the MH2 domain of Smad2, 3, and 4 and the second zinc finger and the COOH-terminal basic domain of GATA4. The COOH-terminal activation domain and the Smad-interacting second zinc finger domain of GATA4 were required for the synergistic activation of the IFABP promoter. Naturally occurring oncogenic mutations within the GATA4-interacting MH2 domain of Smad2 reduced the coactivation of IFABP promoter by Smad2 and GATA4. Our results suggest that the TGF-beta signaling regulates gut epithelial gene expression by targeting GATA4.

Genetic factors in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a relatively common birth defect associated with high mortality and morbidity. Although the exact etiology of most cases of CDH remains unknown, there is a growing body of evidence that genetic factors play an important role in the development of CDH. In this review, we examine key findings that are likely to form the basis for future research in this field. Specific topics include a short overview of normal and abnormal diaphragm development, a discussion of syndromic forms of CDH, a detailed review of chromosomal regions recurrently altered in CDH, a description of the retinoid hypothesis of CDH, and evidence of the roles of specific genes in the development of CDH.

Adrenocortical tumorigenesis, luteinizing hormone receptor and transcription factors GATA-4 and GATA-6

Luteinizing hormone (LH/hCG) responsiveness of normal and pathological human adrenal glands as well as the possibility of constitutive expressions of luteinizing hormone receptor (LHR) in adrenal cortex has been reported. Some recent studies showed a correlation between the LHR and abundant GATA-4 expression in both metastasizing and non-metastasizing human adrenocortical tumors, but not in normal adrenals, implicating the putative relevance of LHR and GATA-4 for adrenocortical pathophysiology. However, the physio- and pathophysiological significance of LHR and GATA-4 in the mechanism of adrenocortical tumorigenesis remains unclear. The paucity of suitable models for adrenal tumorigenesis makes the establishment of proper animal models highly important. LHR expression in the murine adrenal gland is an exception and not found in wild-type (WT) animal. We have previously shown that ectopic LHR expression in the murine adrenal gland can be induced by chronically elevated LH levels. We have generated a gonadotropin-responsive adrenal tumor model in gonadectomized transgenic (TG) mice expressing the inhibin alpha promoter/Simian Virus 40 T antigen transgene (inhalpha/Tag). Given the induction of expression and regulation of GATA-4 and GATA-6 zinc finger transcription factors in the gonads by gonadotropins, this review will explore their relationship to LHR expression and their role in adrenocortical tumorigenesis. A functional link between LHR and GATA-4 actions in the adrenal pathophysiology is proposed.

Disabled-2 is an epithelial surface positioning gene

The formation of the primitive endoderm layer on the surface of the inner cell mass is one of the earliest epithelial morphogenesis in mammalian embryos. In mouse embryos deficient of Disabled-2 (Dab2), the primitive endoderm cells lose the ability to position on the surface, resulting in defective morphogenesis. Embryonic stem cells lacking Dab2 are also unable to position on the surface of cell aggregates and fail to form a primitive endoderm outer layer in the embryoid bodies. The cellular function of Dab2, a cargo-selective adaptor, in mediating endocytic trafficking of clathrin-coated vesicles is well established. We show here that Dab2 mediates directional trafficking and polarized distribution of cell surface proteins such as megalin and E-cadherin and propose that loss of polarity is the underlying mechanism for the loss of epithelial cell surface positioning in Dab2-deficient embryos and embryoid bodies. Thus, the findings indicate that Dab2 is a surface positioning gene and suggest a novel mechanism of epithelial cell surface targeting.

Gene expression pattern and progression of embryogenesis in the immediate post-implantation period of mouse development

During development of the mouse conceptus from implantation to the early gastrula stage, a multitude of genes encoding structural proteins, transcription factors and components of signalling pathways are expressed in the extraembryonic and embryonic tissues derived from the trophectoderm and the inner cell mass. Some genes are expressed widely in the extraembryonic ectoderm, the visceral endoderm or the epiblast, while others display more restricted expression domains in these tissues or are expressed upon the specification of the germ layers at gastrulation. Overall, the developmental changes in gene expression mirror key events of embryogenesis, and reveal the regionalization of signalling activity and the emergence of tissue patterning.

Impaired mesenchymal cell function in Gata4 mutant mice leads to diaphragmatic hernias and primary lung defects

Congenital diaphragmatic hernia (CDH) is an often fatal birth defect that is commonly associated with pulmonary hypoplasia and cardiac malformations. Some investigators hypothesize that this constellation of defects results from genetic or environmental triggers that disrupt mesenchymal cell function in not only the primordial diaphragm but also the thoracic organs. The alternative hypothesis is that the displacement of the abdominal viscera in the chest secondarily perturbs the development of the heart and lungs. Recently, loss-of-function mutations in the gene encoding FOG-2, a transcriptional co-regulator, have been linked to CDH and pulmonary hypoplasia in humans and mice. Here we show that mutagenesis of the gene for GATA-4, a transcription factor known to functionally interact with FOG-2, predisposes inbred mice to a similar set of birth defects. Analysis of wild-type mouse embryos demonstrated co-expression of Gata4 and Fog2 in mesenchymal cells of the developing diaphragm, lungs, and heart. A significant fraction of C57Bl/6 mice heterozygous for a Gata4 deletion mutation died within 1 day of birth. Developmental defects in the heterozygotes included midline diaphragmatic hernias, dilated distal airways, and cardiac malformations. Heterozygotes had any combination of these defects or none. In chimeric mice, Gata4(-/-) cells retained the capacity to contribute to cells in the diaphragmatic central tendon and lung mesenchyme, indicating that GATA-4 is not required for differentiation of these lineages. We conclude that GATA-4, like its co-regulator FOG-2, is required for proper mesenchymal cell function in the developing diaphragm, lungs, and heart.

Multipotent flk-1+ cardiovascular progenitor cells give rise to the cardiomyocyte, endothelial, and vascular smooth muscle lineages

Cell-tracing studies in the mouse indicate that the cardiac lineage arises from a population that expresses the vascular endothelial growth factor receptor 2 (VEGFR2, Flk-1), suggesting that it may develop from a progenitor with vascular potential. Using the embryonic stem (ES) cell differentiation model, we have identified a cardiovascular progenitor based on the temporal expression of the primitive streak (PS) marker brachyury and Flk-1. Comparable progenitors could also be isolated from head-fold stage embryos. When cultured with cytokines known to function during cardiogenesis, individual cardiovascular progenitors generated colonies that displayed cardiomyocyte, endothelial, and vascular smooth muscle (VSM) potential. Isolation and characterization of this previously unidentified population suggests that the mammalian cardiovascular system develops from multipotential progenitors.

Single-cell-derived mesenchymal stem cells overexpressing Csx/Nkx2.5 and GATA4 undergo the stochastic cardiomyogenic fate and behave like transient amplifying cells

Bone marrow-derived stromal cells can give rise to cardiomyocytes as well as adipocytes, osteocytes, and chondrocytes in vitro. The existence of mesenchymal stem cells has been proposed, but it remains unclear if a single-cell-derived stem cell stochastically commits toward a cardiac lineage. By single-cell marking, we performed a follow-up study of individual cells during the differentiation of 9-15c mesenchymal stromal cells derived from bone marrow cells. Three types of cells, i.e., cardiac myoblasts, cardiac progenitors and multipotent stem cells were differentiated from a single cell, implying that cardiomyocytes are generated stochastically from a single-cell-derived stem cell. We also demonstrated that overexpression of Csx/Nkx2.5 and GATA4, precardiac mesodermal transcription factors, enhanced cardiomyogenic differentiation of 9-15c cells, and the frequency of cardiomyogenic differentiation was increased by co-culturing with fetal cardiomyocytes. Single-cell-derived mesenchymal stem cells overexpressing Csx/Nkx2.5 and GATA4 behaved like cardiac transient amplifying cells, and still retained their plasticity in vivo.

The proximal Gata4 promoter directs reporter gene expression to sertoli cells during mouse gonadal development

The GATA4 transcription factor is an important developmental determinant for many organs, such as the heart, gut, and testis. Despite this pivotal role, our understanding of the transcriptional mechanisms that control the proper spatiotemporal expression of the GATA4 gene remains limited. We have generated transgenic mice expressing a green fluorescent protein (GFP) marker under the control of rat Gata4 5' flanking sequences. Several GATA4-expressing organs displayed GFP fluorescence, including the heart, intestine, and pancreas. In the gonads, while GATA4 is expressed in pregranulosa, granulosa, and theca ovarian cells, and Sertoli, Leydig, and peritubular testicular cells, the first 5 kb of Gata4 regulatory sequences immediately upstream of exon 1 were sufficient to direct GFP reporter expression only in testis and, specifically, in Sertoli cells. Onset of GFP expression occurred after Sertoli cell commitment and was maintained in these cells throughout development to adulthood. In vitro studies revealed that the first 118 bp of the Gata4 promoter is sufficient for full basal activity in several GATA4-expressing cell lines. Promoter mutagenesis and DNA-binding experiments identified two GC-box motifs and, particularly, one E-box element within this -118-bp region that are crucial for its activity. Further analysis revealed that members of the USF family of transcription factors, especially USF2, bind to and activate the Gata4 promoter via this critical E-box motif.

Role of metal-responsive transcription factor-1 (MTF-1) in EGF-dependent DNA synthesis in primary hepatocytes

Metal-responsive transcription factor-1 (MTF-1), which is involved in sensing heavy metal load, induces the transcription of several protective genes. The mouse Mtf-1 gene is essential, and Mtf-1(-/-) embryos die from liver degeneration. We showed that DNA synthesis induced in hepatocytes by epidermal growth factor (EGF) was delayed by inhibition of MTF-1. To inhibit MTF-1 activity, MTFDeltaC, a C-terminal deletion mutant of MTF-1, was expressed by infection with the virus Ad5MTFDeltaC. Lactate dehydrogenase (LDH) release and/or caspase-3/7 activation was not observed under our experimental conditions. The inhibitory effect of MTFDeltaC on EGF-dependent DNA synthesis in hepatocytes was not eliminated by zinc addition. EGF-dependent extracellular signal-related kinase (ERK) phosphorylation, an essential reaction for EGF-dependent DNA synthesis, was decreased in MTF-1-inhibited hepatocytes. Moreover, decrease of ERK phosphorylation was observed by using siRNA in MTF-1-downregulated hepatocytes. These results indicate that MTF-1 is particularly important for proper hepatocyte proliferation. This is the first report to suggest the function of MTF-1 in the ERK pathway.

Apical membrane and junctional complex formation during simple epithelial cell differentiation of F9 cells

Epithelium formation is a common event in animal morphogenesis. It has been reported that F9 cells differentiate into visceral endoderm-like epithelial cells when cell aggregates are cultured in the presence of retinoic acid. The present investigation set out to determine whether this in vitro model could be used under monolayer culture conditions, which is suitable for a detailed analysis of epithelial differentiation. We performed comparative gene expression analyses of F9 cells grown under aggregate and monolayer culture conditions prior to and following treatment with retinoic acid. Under these conditions, induction in the expression of differentiation marker genes was confirmed, even in monolayer cultures. Junctional complex and apical membrane formation, both of which are characteristic of epithelial cells, were also observed under monolayer culture conditions. Because of the merit of monolayer culture condition, we found that apical membrane and junctional complex formation are strictly regulated during epithelial differentiation. It was also revealed that F9 cells differentiated into epithelial cells predominantly on the fourth and fifth day following retinoic acid induction. These results showed that a monolayer culture of F9 cells represents a viable in vitro model that can be employed to elucidate mechanisms pertaining to epithelium formation.

Analysis of nuclear reprogramming in cloned miniature pig embryos by expression of Oct-4 and Oct-4 related genes

Xenotransplantation is a rapidly expanding field of research and cloned miniature pigs have been considered as a model animal for it. However, the efficiency of somatic cell nuclear transfer (SCNT) is extremely low, with most clones resulting in early lethality and several kinds of aberrant development. A possible explanation for the developmental failure of SCNT embryos is insufficient reprogramming of the somatic cell nucleus by the oocyte. In order to test this, we analyzed the reprogramming capacity of differentiated fibroblast cell nuclei and embryonic germ cell nuclei with Oct-4 and Oct-4 related genes (Ndp5211, Dppa2, Dppa3, and Dppa5), which are important for embryonic development, Hand1 and GATA-4, which are important for placental development, as molecular markers using RT-PCR. The Oct-4 expression level was significantly lower (P<0.05) in cloned hatched blastocysts derived from fibroblasts and many of fibroblast-derived clones failed to reactivate at least one of the tested genes, while most of the germ cell clones and control embryos correctly expressed these genes. In conclusion, our results suggest that the reprogramming of fibroblast-derived cloned embryos is highly aberrant and this improper reprogramming could be one reason of the early lethality and post-implantation anomalies of somatic cell-derived clones.

Quantitative Oct4 Overproduction in Mouse Embryonic Stem Cells Results in Prolonged Mesoderm Commitment During Hematopoietic Differentiation In Vitro

The Oct4 transcription factor is essential for the self-renewal and pluripotency of embryonic stem cells (ESCs). Oct4 level also controls the fate of ESCs. We analyzed the effects of Oct4 overproduction on the hematopoietic differentiation of ESCs. Oct4 was introduced into ESCs via a bicistronic retroviral vector, and cells were selected on the basis of Oct4 production, with Oct4(+) and Oct4(2+) displaying twofold and three- to fourfold overproduction, respectively. Oct4 overproduction inhibited hematopoietic differentiation in a dose-dependent manner, after the induction of such differentiation by the formation of day 6 embryoid bodies (EB6). This effect resulted from defective EB6 formation rather than from defective hematopoietic differentiation. In contrast, when hematopoiesis was induced by the formation of blast colonies, the effects of Oct4 depended on the level of overproduction: twofold overproduction increased hematopoietic differentiation, whereas higher levels of overproduction markedly inhibited hematopoietic development. This increase or maintenance of Oct4 levels appears to alter the kinetics and pattern of mesoderm commitment, thereby modifying hemangioblast generation. These results demonstrate that Oct4 acts as a master regulator of ESC differentiation.

Gata6 is an important regulator of mouse pancreas development

Gata4, Gata5, and Gata6 represent a subfamily of zinc-finger transcriptional regulators that are important in the development and differentiation of numerous tissues, including many endodermally-derived organs. We demonstrate that Gata4 and Gata6 have overlapping expression patterns in the early pancreatic epithelium. Later, Gata4 becomes restricted to exocrine tissue and Gata6 becomes restricted to a subset of endocrine cells. In addition, we show Gata6, but not Gata4, physically interacts with Nkx2.2, an essential islet transcription factor. To begin determining the roles that Gata4 and Gata6 play during pancreatic development, we expressed Gata4-Engrailed and Gata6-Engrailed dominant repressor fusion proteins in the pancreatic epithelium and in the islet. At e17.5, transgenic Gata6-Engrailed embryos exhibit two distinct phenotypes: a complete absence of pancreas or a reduction in pancreatic tissue. In the embryos that do form pancreas, there is a significant reduction of all pancreatic cell types, with the few differentiated endocrine cells clustered within, or in close proximity to, enlarged ductal structures. Conversely, the majority of transgenic Gata4-Engrailed embryos do not have a pancreatic phenotype. This study suggests that Gata6 is an important regulator of pancreas specification.

Expression of endoderm stem cell markers: evidence for the presence of adult stem cells in human thyroid glands

OBJECTIVE

Adult stem cells have been detected in several human tissues. The object of this study was to investigate whether they also occur in the human thyroid gland.

DESIGN

The expression of the stem cell marker Oct- 4 and the early endodermal markers GATA-4 and HNF4alpha was analyzed in histologic slides and cultured cells derived from goiters, in the FRTL5 cell line, and the HTh74, HTC, C643, and XTC133 thyroid carcinoma cell lines.

MAIN OUTCOME

Stem cell markers were detectable in all primary cultures whereas in the differentiated FRTL5 cell line no expression was observed. Expression of stem cell marker mRNA was not affected by thyrotropin (TSH) stimulation and did not decrease when cells underwent several passages. Immunostaining of cultured cells and of histologic slides of goitrous tissues showed only single cells that were immunoreactive for Oct-4, GATA-4, and HNF4a. Expression of Oct-4 but not of endodermal marker GATA-4 was also detectable in some thyroid carcinoma cell lines. Fluorescence-activated cell sorter (FACS) analysis demonstrated cell populations that were positive for either Oct-4, GATA-4, or HNF4alpha but negative for thyroglobulin. When these putative, FACS-sorted stem cell populations were further analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR), expression of all stem cell markers and of Pax8 but not of thyroglobulin mRNA was detectable.

CONCLUSIONS

These data provide evidence for the presence of adult stem and precursor cells of endodermal origin in the human thyroid gland.

Changes in S1P1 and S1P2 expression during embryonal development and primitive endoderm differentiation of F9 cells

Sphingosine 1-phosphate (S1P) is a ligand for S1P family receptors (S1P(1)-S1P(5)). Of these receptors, S1P(1), S1P(2), and S1P(3) are ubiquitously expressed in adult mice, while S1P(4) and S1P(5) are tissue specific. However, little is known of their expression during embryonal development. We performed Northern blot analyses in mouse embryonal tissue and found that such expression is developmentally regulated. We also examined the expression of these receptors during primitive endoderm (PrE) differentiation of mouse F9 embryonal carcinoma (EC) cells, a well-known in vitro endoderm differentiation system. S1P(2) mRNA was abundantly expressed in F9 EC cells, but little S1P(1) and no S1P(3), S1P(4), or S1P(5) mRNA was detectable. However, S1P(1) mRNA expression was induced during EC-to-PrE differentiation. Studies using small interference RNA of S1P(1) indicated that increased S1P(1) expression is required for PrE differentiation. Thus, S1P(1) may play an important function in PrE differentiation that is not substituted for by S1P(2).

The GATA factor AreA regulates localization and in vivo binding site occupancy of the nitrate activator NirA

The GATA factor AreA is a wide-domain regulator in Aspergillus nidulans with transcriptional activation and chromatin remodelling functions. AreA interacts with the nitrate-specific Zn(2)-C(6) cluster protein NirA and both proteins cooperate to synergistically activate nitrate-responsive genes. We have previously established that NirA in vivo DNA binding site occupancy is AreA dependent and in this report we provide a mechanistic explanation for our previous findings. We now show that AreA regulates NirA at two levels: (i) through the regulation of nitrate transporters, AreA affects indirectly the subcellular distribution of NirA which rapidly accumulates in the nucleus following induction; (ii) AreA directly stimulates NirA in vivo target DNA occupancy and does not act indirectly by chromatin remodelling. Simultaneous overexpression of NirA and the nitrate transporter CrnA bypasses the AreA requirement for NirA binding, permits utilization of nitrate and nitrite as sole N-sources in an areA null strain and leads to an AreA-independent nucleosome loss of positioning.

Mechanisms of self-renewal in human embryonic stem cells

Embryonic stem cells (ESCs) are the pluripotent cell population derived from the inner cell mass of pre-implantation embryos and are characterised by prolonged self-renewal and the potential to differentiate into cells representing all three germ layers both in vitro and in vivo. Preservation of the undifferentiated status of the ESC population requires the maintenance of self-renewal whilst inhibiting differentiation and regulating senescence and apoptosis. In this review, we discuss the intrinsic and extrinsic factors associated with self-renewal process, together with possible signalling pathway interactions and mechanisms of regulation.

Wnt2 is a direct downstream target of GATA6 during early cardiogenesis

The GATA4, 5 and 6 subfamily of transcription factors are potent transactivators of transcription expressed within the precardiac mesoderm. However, little is known of the immediate downstream targets of GATA-factor regulation during the earliest stages of cardiogenesis. Using the P19-CL6 embryonal carcinoma (EC) cell line as an in vitro model of cardiogenesis, we show that GATA6 is the most abundantly expressed of the GATA factors in presumptive cardiac cells. Consequently, we performed a microarray screen comparing mRNA from control EC cells, early in the cardiac differentiation pathway, with those in which GATA6 had been overexpressed. These studies identified 103 genes whose expression changed significantly and this was verified in a representative array of these genes by real-time RT-PCR. We show that early cardiac expression of one of these genes, Wnt2, mirrors that of GATA6 in vitro and in vivo. In addition, its upregulation by GATA6 in differentiating EC cells is mediated by the direct binding of GATA-factor(s) to the cognate Wnt2 promoter, suggesting Wnt2 is an immediate downstream target of GATA-factor regulation during early cardiogenesis.

The TGFβ activated kinase TAK1 regulates vascular development in vivo

TGFβ activated kinase 1 (TAK1) is a MAPKKK that in cell culture systems has been shown to act downstream of a variety of signaling molecules,including TGFβ. Its role during vertebrate development, however, has not been examined by true loss-of-function studies. In this report, we describe the phenotype of mouse embryos in which the Tak1 gene has been inactivated by a genetrap insertion. Tak1 mutant embryos exhibit defects in the developing vasculature of the embryo proper and yolk sac. These defects include dilation and misbranching of vessels, as well as an absence of vascular smooth muscle. The phenotype of Tak1 mutant embryos is strikingly similar to that exhibited by loss-of-function mutations in the TGFβ type I receptor Alk1 and the type III receptor endoglin,suggesting that TAK1 may be a major effector of TGFβ signals during vascular development. Consistent with this view, we find that in zebrafish,morpholinos to TAK1 and ALK1 synergize to enhance the Alk1 vascular phenotype. Moreover, we show that overexpression of TAK1 is able to rescue the vascular defect produced by morpholino knockdown of ALK1. Taken together,these results suggest that TAK1 is probably an important downstream component of the TGFβ signal transduction pathway that regulates vertebrate vascular development. In addition, as heterozygosity for mutations in endoglin and ALK1 lead to the human syndromes known as hereditary hemorrhagic telangiectasia 1 and 2, respectively, our results raise the possibility that mutations in human TAK1 might contribute to this disease.

Congenital heart diseases in small animals: part I. Genetic pathways and potential candidate genes

Proper cardiac morphogenesis requires a series of specific cell and tissue interactions driven by several cardiac transcription factors and downstream cardiac genes. To date, a number of genetic aetiologies responsible for human congenital heart defects (CHDs) have been identified, although none has been found for CHDs in small animals. Most gene mutations responsible for human CHDs exist in genetic pathways associated with cardiomorphogenesis. Insights into cardiomorphogenesis from human and mouse genetic studies will help us to identify potential genetic aetiologies in CHDs in small animals. Therefore, in this first part of a two-part review, the major genetic pathways for cardiomorphogenesis and important candidate genes for CHDs, based on mouse knock-out and human genetic studies are discussed.

Histone acetyltransferase activity of p300 is required for the promotion of left ventricular remodeling after myocardial infarction in adult mice in vivo

BACKGROUND

Left ventricular (LV) remodeling after myocardial infarction is associated with hypertrophy of surviving myocytes and represents a major process that leads to heart failure. One of the intrinsic histone acetyltransferases, p300, serves as a coactivator of hypertrophy-responsive transcriptional factors such as a cardiac zinc finger protein GATA-4 and is involved in its hypertrophic stimulus-induced acetylation and DNA binding. However, the role of p300-histone acetyltransferase activity in LV remodeling after myocardial infarction in vivo is unknown.

METHODS AND RESULTS

To solve this problem, we have generated transgenic mice overexpressing intact p300 or mutant p300 in the heart. As the result of its 2-amino acid substitution in the p300-histone acetyltransferase domain, this mutant lost its histone acetyltransferase activity and was unable to activate GATA-4-dependent transcription. The two kinds of transgenic mice and the wild-type mice were subjected to myocardial infarction or sham operation at the age of 12 weeks. Intact p300 transgenic mice showed significantly more progressive LV dilation and diminished systolic function after myocardial infarction than wild-type mice, whereas mutant p300 transgenic mice did not show this.

CONCLUSIONS

These findings demonstrate that cardiac overexpression of p300 promotes LV remodeling after myocardial infarction in adult mice in vivo and that histone acetyltransferase activity of p300 is required for these processes.

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

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.

Characterization and in vitro differentiation potential of a new human embryonic stem cell line, ReliCell®hES1

Human embryonic stem cells (hESCs) are an exceptionally useful tool for studies of human development and represent a potential source for transplantation therapies. At present, only a limited number of hESCs lines representing a very small sample of genetic diversity of the human populations are available. Here, we report the derivation and characterization of a new hESC line, ReliCellhES1. These cells, established from the inner cell mass (ICM) on mouse embryonic feeder (MEF) layer, satisfy the criteria that characterize pluripotent hESCs: The cell line expresses high levels of cell surface markers (such as SSEA-3, SSAEA-4, TRA-1-60 and TRA-1-81), transcription factor Oct-4, alkaline phosphatase (AP) and telomerase. The cell line retains normal karyotype in long-term culture and has a distinct identity as revealed by DNA fingerprinting by short tandem repeat (STR) analysis. Further, upon examination of the in vitro differentiation potential, ReliCellhES1 was found to be capable of giving rise to dopaminergic neurons, cardiomyocytes, pancreatic islets, and hepatocyte-like cells belonging to ectoderm, mesoderm, and endoderm lineages, respectively. To our knowledge, this is the first report of a well-characterized hES cell line from the Indian subcontinent.

Cardiovascular genomics: a current overview of in vivo and in vitro studies

The cardiovascular system is the first system that is developed in the embryo. The cardiovascular development is a complex process involving the coordination, differentiation, and interaction of distinct cell lineages to form the heart and the diverse array of arteries, veins, and capillaries required to supply oxygen and nutrients to all tissues. Embryonic stem cells have been proposed as an interesting model system to investigate molecular and cellular mechanisms involved in mammalian development. The present review is focused on extrinsic soluble factors, intrinsic transcription factors, receptors, signal transduction pathways, and genes regulating the development of cardiovascular system in vivo and in vitro. Special emphasis has been given to cardiovascular genomics including gene expression studies on the cardiovascular system under developmental and pathophysiological conditions.

GATA-4 Gene Organization and Analysis of Its Promoter

The mouse GATA-4 gene is separated by six introns, and this gene organization is conserved in rodents and man. The transcriptional start site of the GATA-4 gene is essentially the same in rat heart, stomach and testis, and in cultured cells expressing GATA-4 such as TM3, TM4, I-10 and P19.CL6 cells. The 5'-upstream of the GATA-4 gene is also conserved in rodents and man. We examined its promoter activity by means of luciferase reporter gene assay using testis-derived TM3 and TM4 cells. The GC-boxes and E-box located in the several tens of base pairs upstream of the transcriptional start sites of the GATA-4 gene were found to be critical for its promoter activity in these cells, consistent with the mode of transcription characteristics of the TATA-less promoter. P19.CL6 cells differentiate into beating cardiomyocytes upon induction by DMSO, accompanied by stimulation of the transcription of heart-specific genes including GATA-4. Interestingly, they exhibit increased luciferase reporter gene activity upon induction by DMSO. Both proximal tandem GC-boxes and the E-box are also contributed to the reporter gene activity in P19.CL6 cells.

Cardiac repair by embryonic stem-derived cells

Cell transplantation approaches offer the potential to promote regenerative growth of diseased hearts. It is well established that donor cardiomyocytes stably engraft into recipient hearts when injected directly into the myocardial wall. Moreover, the transplanted donor cardiomyocytes participate in a functional syncytium with the host myocardium. Thus, transplantation of donor cardiomyocytes resulted in at least partial restoration of lost muscle mass. It is also well established that embryonic stem (ES) cells differentiate into cells of ecto-, endo-, and mesodermal lineages when cultured under appropriate conditions in vitro. Robust cardiomyogenic differentiation was frequently observed in spontaneously differentiating ES cultures. Cellular, molecular and physiologic analyses indicated that ES-derived cells were bona fide cardiomyocytes, with in vitro characteristics typical for cells obtained from early stages of cardiac development. Thus, ES-derived cardiomyocytes constitute a viable source of donor cells for cell transplantation therapies.

GATA Transcription Factors and Hematological Diseases

The development of mature blood cells from hematopoietic stem cells is regulated by transcription factors that control and coordinate the expression of lineage-specific genes. The GATA family consists of six transcription factors that function in hematopoietic and endodermal development. Among them, GATA-1 is expressed in erythroid, megakaryocytic, eosinophil and mast cell lineages, and GATA-2 is expressed in stem and progenitor cells, at more immature stage compared with GATA-1. Based on the characteristic phenotypes of GATA-1 and GATA-2 mutant mice, it has been suggested that mutations of these GATA genes in humans may result in the onset of certain clinical diseases. To date, mutations of GATA-1 gene have been found in inherited anemia and thrombocytopenia, and Down syndrome-related acute leukemia, which exhibits megakaryocytic phenotypes and frequently occurs in patients with Down syndrome. In contrast, no mutation of GATA-2 gene has been identified in hematological diseases; however, we found the expression level of GATA-2 is significantly decreased in CD34 positive cells in patients with aplastic anemia. Since GATA-2 functions in the proliferation of hematopoietic stem cells, the reduction of GATA-2 expression in CD34 positive cells may result in the decreased number of hematopoietic stem cells, which is the characteristic feature of aplastic anemia. Based on these lines of evidence, some types of hematological diseases may be defined as transcription factor diseases.

GATA factors as key regulatory molecules in the development of Drosophila endoderm

Essential roles for GATA factors in the development of endoderm have been reported in various animals. A Drosophila GATA factor gene, serpent (srp, dGATAb, ABF), is expressed in the prospective endoderm, and loss of srp activity causes transformation of the prospective endoderm into ectodermal foregut and hindgut, indicating that srp acts as a selector gene to specify the developmental fate of the endoderm. While srp is expressed in the endoderm only during early stages, it activates a subsequent GATA factor gene, dGATAe, and the latter continues to be expressed specifically in the endoderm throughout life. dGATAe activates various functional genes in the differentiated endodermal midgut. An analogous mode of regulation has been reported in Caenorhabditis elegans, in which a pair of GATA genes, end-1/3, specifies endodermal fate, and a downstream pair of GATA genes, elt-2/7, activates genes in the differentiated endoderm. Functional homology of GATA genes in nature is apparently extendable to vertebrates, because endodermal GATA genes of C. elegans and Drosophila induce endoderm development in Xenopus ectoderm. These findings strongly imply evolutionary conservation of the roles of GATA factors in the endoderm across the protostomes and the deuterostomes.

Developmental control via GATA factor interplay at chromatin domains

Despite the extraordinary task of packaging mammalian DNA within the constraints of a cell nucleus, individual genes assemble into cell type-specific chromatin structures with high fidelity. This chromatin architecture is a crucial determinant of gene expression signatures that distinguish specific cell types. Whereas extensive progress has been made on defining biochemical and molecular mechanisms of chromatin modification and remodeling, many questions remain unanswered about how cell type-specific chromatin domains assemble and are regulated. This mini-review will discuss emerging studies on how interplay among members of the GATA family of transcription factors establishes and regulates chromatin domains. Dissecting mechanisms underlying the function of hematopoietic GATA factors has revealed fundamental insights into the control of blood cell development from hematopoietic stem cells and the etiology of pathological states in which hematopoiesis is perturbed.

GATA factors lie upstream of Nkx 2.5 in the transcriptional regulatory cascade that effects cardiogenesis

Members of the GATA-4, -5, and -6 subfamily of transcription factors are co-expressed with the homeoprotein Nkx 2.5 in the precardiac mesoderm during the earliest stages of its specification and are known to be important determinants of cardiac gene expression. Ample evidence suggests that GATA factors and Nkx 2.5 cross-regulate each other's expression; however, the temporal order of the expression of these transcription factors in vivo remains unresolved, and thus precise definition of the role of the products of the genes they transcribe in early development has been difficult to assess. We employed P19 CL6 mouse embryonic carcinoma cells as a model to investigate this problem, because these cells, like embryonic stem cells, can be induced to differentiate along multiple lineages. Here we demonstrate that when P19 CL6 cells are induced to differentiate to a cardiogenic lineage, the expression of GATA-4 and GATA-6 is up-regulated prior to the transcriptional activation of Nkx 2.5. Moreover, over-expression of GATA-4 or -6 at the time of Nkx 2.5 induction results in a significant up-regulation of endogenous Nkx 2.5 transcription. Finally, it is known that a Nkx-dependent enhancer is necessary for GATA-6 expression within cardiomyocytes of the developing mouse embryo. We demonstrate that within undifferentiated P19 CL6 cells, GATA-6 expression is subject to active repression by a novel upstream element that possesses binding sites for factors involved in transcriptional repression that are conserved between mammalian species.

Genetic players in esophageal atresia and tracheoesophageal fistula

Esophageal atresia is a common and serious developmental anomaly, of which the causes remain largely unknown. Studies in vertebrate models indicate the importance of the sonic hedgehog pathway in esophageal atresia, but its relevance to the human condition remains to be defined. Now, three genes have been identified that cause syndromic forms of esophageal atresia when mutated. NMYC and SOX2 are transcription factors, whereas CHD7 is encoded by a chromodomain helicase DNA-binding gene, important for chromatin structure and gene expression. These new genes broaden our view of human foregut development.

Crucial transcription factors in endoderm and embryonic gut development are expressed in gut-like structures from mouse ES cells

Mouse embryonic stem (ES) cells are pluripotent and retain the potential to form an organ similar to the gut showing spontaneous contractions in vitro. The morphological features of these structures and their formation, as assessed using the hanging drop method to produce embryoid bodies (EBs), seem to be similar to those in vivo. To determine whether the same molecular mechanisms are involved in the formation process, the expression pattern of transcription factors regulating endoderm and gut development in the mouse embryo was examined by in situ hybridization and compared with in vivo expression. Expression of gene products was also examined by immunohistochemistry, and expression colocalization was analyzed with double staining. The results showed that all factors examined, that is, Sox17, Id2, HNF3beta/Foxa2, and GATA4, were expressed in both EBs and gut-like structures. Moreover, their expression patterns were similar to those in the mouse embryo. EBs after the hanging drop period and before outgrowth already expressed all factors that were colocalized with each other in EB epithelial structures. These findings suggest that the origin of the gut-like structure is determined during the hanging drop period and that the gut-like structure is formed as the epithelial structure in EBs during the hanging drop period. They also indicate that the in vitro system using mouse ES cells mimics in vivo development and should prove useful in the study of molecular mechanisms for endoderm and gut development.

Perception of differentiation cues by GATA factors in primitive endoderm lineage determination of mouse embryonic stem cells

The formation of the primitive endoderm covering the inner cell mass of early mouse embryos can be simulated in vitro by the differentiation of mouse embryonic stem (ES) cells in culture following either aggregation of suspended cells or stimulation of cell monolayers with retinoic acid. The developmentally regulated transcription factors GATA-4 and GATA-6 have determining role in mouse extraembryonic endoderm development. We analyzed the in vitro differentiation of mouse embryonic stem cells deficient of GATA factors and conclude that GATA-4 is required for ES cells to perceive a cell positioning (cell aggregation) signal and GATA-6 is required to sense morphogenic (retinoic acid) signal. The collaboration between GATA-6 and GATA-4, or GATA-6 and GATA-5 which can substitute for GATA-4, is involved in the perception of differentiation cues by embryonic stem cells in their determination of endoderm lineage. This study indicates that the lineage differentiation of ES cells can be manipulated by the expression of GATA factors.

GATA factors and transcriptional regulation of cardiac natriuretic peptide genes

The A- and B-natriuretic peptides (ANP and BNP) are the heart major secretory products. ANF and BNP expression is a marker of cardiomyocyte differentiation, and is regulated spatially, developmentally and hormonally. Analysis of the ANP and BNP promoters has contributed in a major way to our present understanding of the key regulators of cardiac development. It has also started to unravel the complex combinatorial interactions required for proper regulation of the cardiac genetic program. The GATA family of transcription factors initially identified as essential regulators of the two natriuretic peptide genes appears to be at the heart of the molecular circuits governing cardiac growth and differentiation. In particular, GATA-4 has emerged as the nuclear effector of several signaling pathways which modulate its function through post-translational modifications and protein-protein interactions. This review will cover our current knowledge of cardiac transcription and the role of GATA factors in embryonic and postnatal heart development.