Expression of the chicken GATA factor family during early erythroid development and differentiation

Gata2a Mutation Causes Progressive Microphthalmia and Blindness in Nile Tilapia

The normal development of lens fiber cells plays a critical role in lens morphogenesis and maintaining transparency. Factors involved in the development of lens fiber cells are largely unknown in vertebrates. In this study, we reported that GATA2 is essential for lens morphogenesis in Nile tilapia (Oreochromis niloticus). In this study, Gata2a was detected in the primary and secondary lens fiber cells, with the highest expression in primary fiber cells. gata2a homozygous mutants of tilapia were obtained using CRISPR/Cas9. Different from fetal lethality caused by Gata2/gata2a mutation in mice and zebrafish, some gata2a homozygous mutants of tilapia are viable, which provides a good model for studying the role of gata2 in non-hematopoietic organs. Our data showed that gata2a mutation caused extensive degeneration and apoptosis of primary lens fiber cells. The mutants exhibited progressive microphthalmia and blindness in adulthood. Transcriptome analysis of the eyes showed that the expression levels of almost all genes encoding crystallin were significantly down-regulated, while the expression levels of genes involved in visual perception and metal ion binding were significantly up-regulated after gata2a mutation. Altogether, our findings indicate that gata2a is required for the survival of lens fiber cells and provide insights into transcriptional regulation underlying lens morphogenesis in teleost fish.

MicroRNAs as regulators and effectors of hematopoietic transcription factors

Hematopoiesis is a highly-regulated development process orchestrated by lineage-specific transcription factors that direct the generation of all mature blood cells types, including red blood cells, megakaryocytes, granulocytes, monocytes, and lymphocytes. Under homeostatic conditions, the hematopoietic system of the typical adult generates over 10¹¹ blood cells daily throughout life. In addition, hematopoiesis must be responsive to acute challenges due to blood loss or infection. MicroRNAs (miRs) cooperate with transcription factors to regulate all aspects of hematopoiesis, including stem cell maintenance, lineage selection, cell expansion, and terminal differentiation. Distinct miR expression patterns are associated with specific hematopoietic lineages and stages of differentiation and functional analyses have elucidated essential roles for miRs in regulating cell transitions, lineage selection, maturation, and function. MiRs function as downstream effectors of hematopoietic transcription factors and as upstream regulators to control transcription factor levels. Multiple miRs have been shown to play essential roles. Regulatory networks comprised of differentially expressed lineage-specific miRs and hematopoietic transcription factors are involved in controlling the quiescence and self-renewal of hematopoietic stem cells as well as proliferation and differentiation of lineage-specific progenitor cells during erythropoiesis, myelopoiesis, and lymphopoiesis. This review focuses on hematopoietic miRs that function as upstream regulators of central hematopoietic transcription factors required for normal hematopoiesis. This article is categorized under: RNA in Disease and Development > RNA in Development Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.

The multi-faceted role of Gata3 in developmental haematopoiesis

The transcription factor Gata3 is crucial for the development of several tissues and cell lineages both during development as well as postnatally. This importance is apparent from the early embryonic lethality following germline Gata3 deletion, with embryos displaying a number of phenotypes, and from the fact that Gata3 has been implicated in several cancer types. It often acts at the level of stem and progenitor cells in which it controls the expression of key lineage-determining factors as well as cell cycle genes, thus being one of the main drivers of cell fate choice and tissue morphogenesis. Gata3 is involved at various stages of haematopoiesis both in the adult as well as during development. This review summarizes the various contributions of Gata3 to haematopoiesis with a particular focus on the emergence of the first haematopoietic stem cells in the embryo—a process that appears to be influenced by Gata3 at various levels, thus highlighting the complex nature of Gata3 action.

The emerging role of GATA transcription factors in development and disease

The GATA family of transcription factors consists of six proteins (GATA1-6) which are involved in a variety of physiological and pathological processes. GATA1/2/3 are required for differentiation of mesoderm and ectoderm-derived tissues, including the haematopoietic and central nervous system. GATA4/5/6 are implicated in development and differentiation of endoderm- and mesoderm-derived tissues such as induction of differentiation of embryonic stem cells, cardiovascular embryogenesis and guidance of epithelial cell differentiation in the adult.

SON protein regulates GATA-2 through transcriptional control of the microRNA 23a~27a~24-2 cluster

SON is a DNA- and RNA-binding protein localized in nuclear speckles. Although its function in RNA splicing for effective cell cycle progression and genome stability was recently unveiled, other mechanisms of SON functions remain unexplored. Here, we report that SON regulates GATA-2, a key transcription factor involved in hematopoietic stem cell maintenance and differentiation. SON is highly expressed in undifferentiated hematopoietic stem/progenitor cells and leukemic blasts. SON knockdown leads to significant depletion of GATA-2 protein with marginal down-regulation of GATA-2 mRNA. We show that miR-27a is up-regulated upon SON knockdown and targets the 3'-UTR of GATA-2 mRNA in hematopoietic cells. Up-regulation of miR-27a was due to activation of the promoter of the miR-23a∼27a∼24-2 cluster, suggesting that SON suppresses this promoter to lower the microRNAs from this cluster. Our data revealed a previously unidentified role of SON in microRNA production via regulating the transcription process, thereby modulating GATA-2 at the protein level during hematopoietic differentiation.

Cocaine activates Homer1 immediate early gene transcription in the mesocorticolimbic circuit: differential regulation by dopamine and glutamate signaling

Homer proteins are intracellular scaffolding proteins that, among glutamate receptors, selectively bind to group1 metabotropic glutamate receptors and regulate their trafficking and intracellular signaling. Homer proteins have been implicated in synaptic and behavioral plasticity, including drug-seeking behavior after cocaine treatment. Homer1 gene activation leads to transcription of a variant mRNA (Homer1a), which functions as an immediate early gene. Homer1a competes with the constitutive Homer proteins (Homer1b/c/d, Homer2a/b, Homer3) for binding to group1 metabotropic glutamate and IP3 receptors. Binding of Homer1a to these proteins disrupts their association with the intracellular signaling scaffold and modulates receptor function. In this study, using RT-PCR, activation of Homer1a mRNA transcription in response to acute and repeated administration of cocaine was characterized in prefrontal cortex, nucleus accumbens, and ventral tegmental area, three mesocorticolimbic nuclei of the rat brain. Moreover, the dopaminergic and glutamatergic regulation of Homer1 gene activation by cocaine was investigated. Acute cocaine rapidly and transiently activated transcription of Homer1a mRNA in all three nuclei. However, repeated administration of cocaine was not effective in inducing the Homer1a mRNA transcription after various withdrawal times ranging from 2 h to 3 weeks. The acute cocaine-mediated activation of Homer1 gene was regulated by D1 but not D2 dopamine receptors. The blockade of AMPA or NMDA glutamate receptors did not prevent cocaine-mediated activation of Homer1 gene in the three mesocorticolimbic nuclei. These data indicate that acute administration of cocaine transiently activates Homer1 gene producing the immediate early gene Homer1a mRNA in the three mesocorticolimbic nuclei of the rat brain. Activation of Homer1 gene may contribute to the cocaine-mediated synaptic and behavioral plasticity.

Differential requirements for hematopoietic commitment between human and rhesus embryonic stem cells

Progress toward clinical application of ESC-derived hematopoietic cellular transplantation will require rigorous evaluation in a large animal allogeneic model. However, in contrast to human ESCs (hESCs), efforts to induce conclusive hematopoietic differentiation from rhesus macaque ESCs (rESCs) have been unsuccessful. Characterizing these poorly understood functional differences will facilitate progress in this area and likely clarify the critical steps involved in the hematopoietic differentiation of ESCs. To accomplish this goal, we compared the hematopoietic differentiation of hESCs with that of rESCs in both EB culture and stroma coculture. Initially, undifferentiated rESCs and hESCs were adapted to growth on Matrigel without a change in their phenotype or karyotype. Subsequent differentiation of rESCs in OP9 stroma led to the development of CD34(+)CD45(-) cells that gave rise to endothelial cell networks in methylcellulose culture. In the same conditions, hESCs exhibited convincing hematopoietic differentiation. In cytokine-supplemented EB culture, rESCs demonstrated improved hematopoietic differentiation with higher levels of CD34(+) and detectable levels of CD45(+) cells. However, these levels remained dramatically lower than those for hESCs in identical culture conditions. Subsequent plating of cytokine-supplemented rhesus EBs in methylcellulose culture led to the formation of mixed colonies of erythroid, myeloid, and endothelial cells, confirming the existence of bipotential hematoendothelial progenitors in the cytokine-supplemented EB cultures. Evaluation of four different rESC lines confirmed the validity of these disparities. Although rESCs have the potential for hematopoietic differentiation, they exhibit a pause at the hemangioblast stage of hematopoietic development in culture conditions developed for hESCs.

SCL, GATA-2 and Lmo2 expression in neurogenesis

SCL, Lmo2 and GATA factors form common transcription complexes during hematopoietic differentiation. The overlapping expression of SCL with GATA-2 and GATA-3 in the developing brain indicated that these factors might collaborate also in the course of neural tissue differentiation. The expression pattern of Lmo2 in the developing CNS, however, is not well understood. Here, we show that neural cells in the early embryonic chick mid- and hindbrain express SCL and GATA-2, while Lmo2 is expressed only in vascular elements. The lack of Lmo2 transcripts in neural cells demonstrated that SCL and GATA-2 cannot form common complexes with Lmo2 in the developing brain. In the course of neural tissue genesis, GATA-2 mRNA appeared prior to the SCL transcript. While GATA-2 expression decreased with maturation, SCL expression persisted at a high level also in post-neurogenic periods. The temporal pattern of SCL and GATA-2/3 expression was investigated also in vitro, in the course of induced neurogenesis by NE-4C neural stem cells. While GATA-2 expression increased from the very beginning of differentiation, SCL expression appeared only in more differentiated cells expressing proneural genes. GATA-3 expression, on the other hand, was detected only in advanced stages of the neuronal maturation, which were characterised by the activation of the Math2 neuronal gene. Similarly to the hematopoietic differentiation, GATA-2 expression precedes the activation of both SCL and GATA-3, and may play roles in the activation of the SCL gene in neuronal development. In contrast to hematopoietic differentiation, however, our results failed to demonstrate co-assembling of GATA factors or SCL with Lmo2. While overlapping expression of GATA-2/3 and SCL was detected, Lmo2 activation could not be demonstrated in neural cells in the investigated period of neuronal development.

YY1 and GATA-1 interaction modulate the chicken 3'-side alpha-globin enhancer activity

Studying the chicken alpha-globin domain as a model system of gene regulation, we have previously identified contiguous silencer-enhancer elements located on the 3'-side of the domain. To better characterize the enhancer we performed a systematic functional analysis to define its expression influence range and the ubiquitous and stage-specific transcriptional regulators interacting with this control element. In contrast to previous reports, we found that, in addition to a core element that includes three GATA-1 binding sites, the enhancer incorporates a 120 base-pair DNA fragment where EKLF, NF-E2 and a fourth GATA-1 factor could interact. Functional experiments demonstrate that the enhancer activity over the adult alpha(D) promoter is differentially regulated. We found that the transcriptional factor Ying Yang 1 (YY1) binds to the 120 base-pair DNA fragment and its effect over the enhancer activity is GATA-1-dependent. In addition, we characterize a novel physical interaction between GATA-1 and YY1 that influences the enhancer function. Experiments using a histone deacetylation inhibitor indicate that, in pre-erythroblasts, the enhancer down-regulation could be influenced by a closed chromatin conformation. Our observations show that the originally defined enhancer possesses a more complex composition than previously assumed. We propose that its activity is modulated through differential nuclear factor interactions and chromatin modifications at distinct erythroid stages.

Gene expression analysis of Gata3-/- mice by using cDNA microarray technology

Transcription factor Gata3 is implicated in the formation of autosomal dominant hypoparathyroidism, sensorineural deafness, and renal anomaly (HDR) syndrome. We pursued to identify the potential Gata3 target genes by profiling the gene expression pattern in E9.5 Gata3-/- mouse embryos. Altogether four independent microarray hybridizations were carried out on NIA Mouse15K cDNA arrays. We discovered two hundred and sixty one genes that are downregulated in Gata3 mutant embryos at E9.5 (with a minimal 2.0-fold change). The majority of the differentially expressed genes belong to two functional groups--genes involved in transcription regulation and cellular signaling. One of the genes discovered to be downregulated in Gata3 mutant embryos was tumor suppressor gene Disabled 2. The validity of this finding was checked by using the whole mount in situ hybridization technology. This study revealed that the sites, where Dab2 is downregulated in the mutant embryos partly overlap with the Gata3 expression domains, including the mid-embryo region, branchial arches and facio-acoustic (VII-VIII) neural crest complex. This is the first time when tumor supressor gene Dab2 is shown to be implicated in the defective phenotype of Gata3 mutant mice.

A molecular dissection of the interaction between the transcription factor Gata-1 zinc finger and DNA

The production of circulating blood cells from bone marrow stem cells during hematopoiesis is accompanied by overall changes in gene expression which cause production of required functional proteins, such as hemoglobin in erythroid cells, as well as control of cell growth, preventing apoptosis of differentiating cells. Hematopoietic gene regulation is controlled by several specific transcription factors, including the factor Gata-1, which is required for erythrocyte maturation. Based on contacts observed in the NMR structure of the cGata-1 binding domain in complex with DNA, the protein's key DNA interface is interesting in being quite hydrophobic in nature, due to the presence of three leucine side chains protruding toward the DNA. Given the T-rich composition of the GATA DNA binding site, it is possible that thymine's unique 5-methyl group may mediate some of these hydrophobic contacts to increase the stability of binding. The hypothesis that thymine methyl groups are important to the free energy of binding between Gata and DNA is tested by measuring binding of an oligonucleotide substrate in which individual thymine bases are substituted with uracil. To test for any important base-pair specific interactions which may be hydrogen-bonded in character, we have also assayed Gata binding to oligonucleotides with base analogs which cannot make hydrogen bonds. We report that out of the binding site's five thymine methyl groups, only one appeared to make a notable contribution to binding affinity, with removal causing a loss of less than 1kcal/mol of binding free energy. On the other hand, perturbing the potential hydrogen-bonding surface of the DNAs major groove was found to cause a larger decrease in binding affinity than removal of any of the thymine methyl groups, with a loss of 2-3kcal/mol of binding free energy.

Altered interaction of HDAC5 with GATA-1 during MEL cell differentiation

The transcription factor GATA-1 plays a significant role in erythroid differentiation and association with CBP stimulates its activity by acetylation. It is possible that histone deacetylases (HDACs) repress the activity of GATA-1. In the present study, we investigated whether class I and class II HDACs interact with GATA-1 to regulate its function and indeed, GATA-1 is directly associated with HDAC3, HDAC4 and HDAC5. The expression profiling and our previous observation that GATA-2 interacts with members of the HDAC family prompted us to investigate further the biological relevance of the interaction between GATA-1 and HDAC5. Coexpression of HDAC5 suppressed the transcriptional potential of GATA-1. Our results demonstrated that GATA-1 and HDAC5 colocalized to the nucleus of murine erythroleukemia (MEL) cells. Furthermore, a portion of HDAC5 moved to the cytoplasm concomitant with MEL cell erythroid differentiation, which was induced by treatment with N,N'-hexamethylenebisacetamide. These observations support the suggestion that control of the HDAC5 nucleocytoplasmic distribution might be associated with MEL cell differentiation, possibly through regulated GATA-1 transactivation.

From mesoderm to blood islands: patterns of key molecules during yolk sac erythropoiesis

Several identified genes play key roles in the specification of the blood-forming system, from commitment of mesoderm to differentiation of hemopoietic and endothelial cells. We have thoroughly analyzed the expression dynamics of some of these genes during yolk sac erythropoiesis in the chick embryo. The study includes transcription factors which are known to participate in multimeric complexes: GATA-1, -2, SCL/tal-1 and Lmo2 (whose avian orthologue we have cloned), VEGF-R2, a critical regulator of hemopoietic and endothelial commitment, and hemoglobin used as a marker of the last step in erythroid differentiation. Several findings were unexpected. (1) Two distinct patterns were revealed for GATA-2, first: low expression, ubiquitous in all mesodermal cells, as soon as cells ingress through the primitive streak; secondly: high, blood island-specific expression. (2) VEGF-R2 is coexpressed with GATA-2 at the level of the primitive streak. (3) SCL and Lmo2 expression is restricted to presumptive hemangioblasts. (4) The up-regulation of GATA-2 in newly formed blood islands is shortly followed by GATA-1 expression. (5) Lmo2 is up-regulated in blood island angioblasts thus appearing as one of the earliest markers for endothelial cell commitment. VEGF-R2 is down-regulated in hemopoietic cells prior to GATA-2, SCL/tal-1, Lmo2 and GATA-1 in erythroblasts.

The human beta-globin locus control region

The human beta-globin gene locus is the subject of intense study, and over the past two decades a wealth of information has accumulated on how tissue-specific and stage-specific expression of its genes is achieved. The data are extensive and it would be difficult, if not impossible, to formulate a comprehensive model integrating every aspect of what is currently known. In this review, we introduce the fundamental characteristics of globin locus regulation as well as questions on which much of the current research is predicated. We then outline a hypothesis that encompasses more recent results, focusing on the modification of higher-order chromatin structure and recruitment of transcription complexes to the globin locus. The essence of this hypothesis is that the locus control region (LCR) is a genetic entity highly accessible to and capable of recruiting, with great efficiency, chromatin-modifying, coactivator, and transcription complexes. These complexes are used to establish accessible chromatin domains, allowing basal factors to be loaded on to specific globin gene promoters in a developmental stage-specific manner. We conceptually divide this process into four steps: (a) generation of a highly accessible LCR holocomplex; (b) recruitment of transcription and chromatin-modifying complexes to the LCR; (c) establishment of chromatin domains permissive for transcription; (d) transfer of transcription complexes to globin gene promoters.

Hemangioblast commitment in the avian allantois: cellular and molecular aspects

We recently identified the allantois as a site producing hemopoietic and endothelial cells capable of colonizing the bone marrow of an engrafted host. Here, we report a detailed investigation of some early cytological and molecular processes occurring in the allantoic bud, which are probably involved in the production of angioblasts and hemopoietic cells. We show that the allantois undergoes a program characterized by the prominent expression of several "hemangioblastic" genes in the mesoderm accompanied by other gene patterns in the associated endoderm. VEGF-R2, at least from stage HH17 onward, is expressed and is shortly followed by transcription factors GATA-2, SCL/tal-1, and GATA-1. Blood island-like structures differentiate that contain both CD45(+) cells and cells accumulating hemoglobin; these structures look exactly like blood islands in the yolk sac. This hemopoietic process takes place before the establishment of a vascular network connecting the allantois to the embryo. As far as the endoderm is concerned, GATA-3 mRNA is found in the region where allantois will differentiate before the posterior instestinal portal becomes anatomically distinct. Shortly before the bud grows out, GATA-2 was expressed in the endoderm and, at the same time, the hemangioblastic program became initiated in the mesoderm. GATA-3 is detected at least until E8 and GATA-2 until E3 the latest stage examined for this factor. Using in vitro cultures, we show that allantoic buds, dissected out before the establishment of circulation between the bud and the rest of the embryo, produced erythrocytes of the definitive lineage. Moreover, using heterospecific grafts between chick and quail embryos, we demonstrate that the allantoic vascular network develops from intrinsic progenitors. Taken together, these results extend our earlier findings about the commitment of mesoderm to the endothelial and hemopoietic lineages in the allantois. The detection of a prominent GATA-3 expression restricted to the endoderm of the preallantoic region and allantoic bud, followed by that of GATA-2, is an interesting and novel information, in the context of organ formation and endoderm specification in the emergence of hemopoietic cells.

Erythroid carbonic anhydrase and hsp70 expression in chick embryonic development: role of cAMP and hypoxia

In the second half of avian embryonic development cAMP affects major aspects of red blood cell (RBC) function. At day 13/14, progressive developmental hypoxia causes the release of norepinephrine and erythroid beta-adrenergic receptor stimulation initiates the coordinate induction of adaptive key events of erythroid differentiation like carbonic anhydrase (CAII) and 2,3-biphosphoglycerate synthesis. Although cAMP-dependent regulation of CAII protein synthesis has been described in detail, no data exist about the transcriptional regulation in embryonic RBC. Here we report that after day 12 of embryonic development, the caII mRNA is accumulating. Hypoxic incubation at day 10 as well as in vitro incubation of isolated RBC with cAMP-elevating agonists strongly induces erythroid caII expression. The induction of caII occurs fast and does not require new protein synthesis. By screening several late erythroid genes, we could identify hsp70 as another cAMP-induced gene in definitive RBC. Because caII (but not hsp70) is also induced by cAMP in primitive RBC, the signal may regulate key events of late primitive and definitive erythropoiesis.

Contribution of ventral and dorsal mesoderm to primitive and definitive erythropoiesis in the salamander Hynobius retardatus

Previously, we found that the conversion of hemoglobins (Hbs) from the larval to the adult type occurred within a single erythroid cell population in a salamander, Hynobius retardatus ("Hb switching" model), whereas the transition involves replacement of red-blood-cell (RBC) populations ("RBC replacement" model) in many amphibians (M. Yamaguchi, H. Takahashi, and M. Wakahara, 2000, Dev. Gene Evol. 210, 180-189). To further characterize the Hb transition, developmental changes in the erythropoietic sites have been intensively analyzed using larval- and adult-specific globin antibodies and globin and GATA-3 RNA probes. Cells of the ventral blood island (VBI) and the dorsolateral plate (DLP) in embryos differentiate in situ to erythroid cells that contain larval globin mRNA, suggesting that both the VBI and the DLP contribute to "primitive" erythropoiesis. In contrast, the expression pattern of the GATA-3 gene suggests that cells of the DLP may contribute to "definitive" hematopoiesis. In order to determine whether it is possible to define a definitive erythropoiesis in H. retardatus or not, further experiments were done: (1) when metamorphosing larvae were treated with phenylhydrazine to induce anemia and then bled at the postmetamorphic stage after recovery from the anemia, a precocious Hb transition was observed in these animals; (2) an RBC population expressing only adult Hb was confirmed by subtracting the number of RBCs expressing larval Hb from the total number of RBCs during metamorphosis. All these results support the existence of a definitive erythroid cell population that contributes only adult RBCs in this species.

Targeted deletion of the S-phase-specific Myc antagonist Mad3 sensitizes neuronal and lymphoid cells to radiation-induced apoptosis

The Mad family comprises four basic-helix-loop-helix/leucine zipper proteins, Mad1, Mxi1, Mad3, and Mad4, which heterodimerize with Max and function as transcriptional repressors. The balance between Myc-Max and Mad-Max complexes has been postulated to influence cell proliferation and differentiation. The expression patterns of Mad family genes are complex, but in general, the induction of most family members is linked to cell cycle exit and differentiation. The expression pattern of mad3 is unusual in that mad3 mRNA and protein were found to be restricted to proliferating cells prior to differentiation. We show here that during murine development mad3 is specifically expressed in the S phase of the cell cycle in neuronal progenitor cells that are committed to differentiation. To investigate mad3 function, we disrupted the mad3 gene by homologous recombination in mice. No defect in cell cycle exit and differentiation could be detected in mad3 homozygous mutant mice. However, upon gamma irradiation, increased cell death of thymocytes and neural progenitor cells was observed, implicating mad3 in the regulation of the cellular response to DNA damage.

Levels of GATA-1/GATA-2 transcription factors modulate expression of embryonic and fetal hemoglobins

GATA transcription factors bind the consensus sequence WGATAR, present in the flanking regions of most erythroid specific genes. GATA-1 and GATA-2, coexpressed in erythroid cells, are important for expression of erythroid genes. To elucidate the role of specific GATA transcription factors on globin gene expression, we examined the human alpha- and beta-globin gene clusters for all GATA sites. Conserved GATA sites were found in each of the hypersensitive sites in both beta-and alpha clusters and in proximal regulatory regions of the zeta-, epsilon- and gamma-globin but not the alpha, delta or beta-globin genes. We then tested the effect of increasing levels of GATA-1 and GATA-2 on the expression of endogenous globin genes in human erythroid cells. Increasing GATA-1 levels in K562 cells decreased the levels of epsilon-globin mRNA but had no effect on the levels of expression of gamma, zeta or alpha-globin genes. Increasing GATA-2 levels increased epsilon-globin and gamma-globin transcripts. Increasing levels of GATA-1 also caused a decrease in the expression of endogenous GATA-2, while increased levels of GATA-2 had no effect on GATA-1 mRNA. Our results indicate a differential role of GATA-1 and -2 transcription factors on globin transcripts and suggest a correlation between the conservation of GATA sites in the regulatory regions and the ability of endogenous globin genes to respond to GATA transcription factors. They also suggest that quantitative changes in the levels of GATA-1 or GATA-2 can result in alterations of globin target gene expression and may participate in the ontogenic control of the globin genes.

Glutamate regulates kainate-binding protein expression in cultured chick Bergmann glia through an activator protein-1 binding site

The expression of the chick kainate-binding protein, a member of the ionotropic glutamate receptor family, is restricted to the cerebellum, specifically to Bergmann glia. Glutamate induces a membrane to nuclei signaling involved in gene expression regulation. Exposure of cultured chick Bergmann glia cells to glutamate leads to an increase in kainate binding protein and mRNA levels, suggesting a transcriptional level of regulation. The 5' proximal region of the chick kainate binding gene was cloned and transfected 4into Bergmann glia cells. Three main regulatory regions could be defined, a minimal promoter region, a negative regulatory region, and interestingly, a glutamate-responsive element. Deletion of this element abolishes the agonist effect. Moreover, electrophoretic mobility shift assays, cotransfection experiments, and site-directed mutagenesis clearly suggest that the glutamate effect is mediated through an AP-1 site by a Fos/Jun heterodimer. The present results favor the notion of a functional role of kainate-binding protein in glutamatergic cerebellar neurotransmission.

GATA2 is required for the generation of V2 interneurons

During embryogenesis, transcription factor GATA2 is expressed in a variety of distinct cell types, and earlier experiments showed that GATA2 is a vital regulator of both hematopoiesis and urogenital development. Despite the fact that GATA2 is expressed early and abundantly in the nervous system, there has been no demonstration of its direct participation in neurogenesis. We show here that GATA2 is expressed in the ventral spinal cord exclusively in newly generated V2 interneurons, suggesting that GATA2 might be required for the generation of this discrete neuronal population. Proof for this hypothesis was provided by showing that the number of cells expressing V2 neuronal markers was drastically diminished in gata2 null mutant embryos. The tissue-specific enhancer that directs gata2 transcription specifically in V2 neurons was localized to a 190 bp intragenic element lying within gata2 intron 5, and this element is both necessary and sufficient to confer GATA2 spinal cord expression. The identification of a V2-specific enhancer should allow fundamental new insight into the genetic hierarchy of regulatory events that govern neurogenesis in a well-defined cell lineage.

GLAST: gene expression regulation by phorbol esters

The gene expression regulation of the Na+-dependent high affinity glutamate/aspartate transporter GLAST expressed in cultured Bergmann glia cells from chick cerebellum was studied. A 679 bp fragment of the chick GLAST cDNA was cloned and sequenced. Specific PCR primers were used to quantify chick GLAST mRNA levels. Treatment of the cells with the Ca2+/diacylglycerol dependent protein kinase C (PKC) activator, phorbol 12-tetradecanoyl-13-acetate (TPA) produced a decrease in transporter mRNA levels, without an effect in its mRNA half life, suggesting a transcriptional down regulation. Activation of the cAMP pathway results in a transient decrease in GLAST mRNA levels, in contrast with the TPA effect. These findings suggest that GLAST expression is under control of distinct signaling pathways.

Gata3 loss leads to embryonic lethality due to noradrenaline deficiency of the sympathetic nervous system

Mouse embryos deficient in Gata3 die by 11 days post coitum (d.p.c.) from pathology of undetermined origin. We recently showed that Gata3-directed lacZ expression of a 625-kb Gata3 YAC transgene in mice mimics endogenous Gata3 expression, except in thymus and the sympathoadrenal system. As this transgene failed to overcome embryonic lethality (unpublished data and ref. 3) in Gata3-/- mice, we hypothesized that a neuroendocrine deficiency in the sympathetic nervous system (SNS) might cause embryonic lethality in these mutants. We find here that null mutation of Gata3 leads to reduced accumulation of Th (encoding tyrosine hydroxylase, Th) and Dbh (dopamine beta-hydroxylase, Dbh) mRNA, whereas several other SNS genes are unaffected. We show that Th and Dbh deficiencies lead to reduced noradrenaline in the SNS, and that noradrenaline deficiency is a proximal cause of death in mutants by feeding catechol intermediates to pregnant dams, thereby partially averting Gata3 mutation-induced lethality. These older, pharmacologically rescued mutants revealed abnormalities that previously could not be detected in untreated mutants. These late embryonic defects include renal hypoplasia and developmental defects in structures derived from cephalic neural crest cells. Thus we have shown that Gata3 has a role in the differentiation of multiple cell lineages during embryogenesis.

REDK, a novel human regulatory erythroid kinase

We have identified a novel regulatory erythroid kinase (REDK) that is homologous to a family of dual-specificity kinases. The yeast homolog of REDK negatively regulates cell division, suggesting a similar function for REDK, which is primarily localized in the nucleus. REDK is present in hematopoietic tissues, such as bone marrow and fetal liver, but the RNA is expressed at significant levels only in erythroid or erythropoietin (EPO)-responsive cells. Two novel forms of cDNA (long and short) for REDK have been isolated that appear to be alternative splice products and imply the presence of polypeptides with differing amino termini. The ratio of short-to-long forms of REDK increases dramatically in CD34+ cells cultured with EPO, suggesting differing regulation and function for each form. REDK is predominantly found in nuclear, rather than cytoplasmic, protein extracts, and immunoprecipitated REDK is active in phosphorylating histones H2b, H3, myelin basic protein, and other coimmunoprecipitated proteins. Antisense REDK oligonucleotides promote erythroid colony formation by human bone marrow cells, without affecting colony-forming unit (CFU)-GM, CFU-G, or CFU-GEMM numbers. Maximal numbers of CFU-E and burst-forming unit–erythroid were increased, and CFU-E displayed increased sensitivity to suboptimal EPO concentrations. The data indicate that REDK acts as a brake to retard erythropoiesis.

Pulmonary hypoplasia in the myogenin null mouse embryo

Although fetal breathing movements are required for normal lung development, there is uncertainty concerning the specific effect of absent fetal breathing movements on pulmonary cell maturation. We set out to evaluate pulmonary development in a genetically defined mouse model, the myogenin null mouse, in which there is a lack of normal skeletal muscle fibers and thus skeletal muscle movements are absent in utero. Significant decreases were observed in lung:body weight ratio and lung total DNA at embryonic days (E)14, E17, and E20. Reverse transcriptase/polymerase chain reaction, in situ immunofluorescence, and electron microscopy revealed early lung cell differentiation in both null and wild-type lungs as early as E14. However at E14, myogenin null lungs had decreased 5'-bromo-2-deoxyuridine incorporation compared with that of wild-type littermates, whereas at E17 and E20, increased Bax immunolabeling and terminal deoxyribonucleotidyl transferase-mediated dUTP-biotin nick-end labeling staining were detected in the myogenin null mice but not in the wild-type littermates. These observations highlight the importance of skeletal muscle contractile activity in utero for normal lung organogenesis. Null mice lacking the muscle-specific transcription factor myogenin exhibit a secondary effect on lung development such that decreased lung cell proliferation and increased programmed cell death are associated with lung hypoplasia.

Lmo2 and GATA-3 associated expression in intraembryonic hemogenic sites

It is now widely accepted that hemopoietic cells born intraembryonically are the best candidates for the seeding of definitive hemopoietic organs. To further understand the mechanisms involved in the generation of definitive hemopoietic stem cells, we analysed the expression of the hemopoietic-related transcription factors Lmo2 and GATA-3 during the early steps of mouse development (7-12 dpc), with a particular emphasis on intraembryonic hemogenic sites. We show here that both Lmo2 and GATA-3 are present in the intraembryonic regions known to give rise to hemopoietic precursors in vitro and in vivo, suggesting that they act together at key points of hemopoietic development. (1) Lmo2 and GATA-3 are expressed in the caudal mesoderm during the phase of intraembryonic precursors determination. (2) A highly transient concomitant expression is observed in the caudal intraembryonic definitive endoderm, suggesting that these factors are involved in the specification of intraembryonic hemopoietic precursors. (3) Lmo2 and GATA-3 are expressed within the hemopoietic clusters located in the aortic floor during fetal liver colonisation. Furthermore, a strong GATA-3 signal allowed us to uncover previously unreported mesodermal aggregates beneath the aorta. A combined in situ and immunocytological analysis strongly suggests that ventral mesodermal GATA-3 patches are involved in the process of intraembryonic stem cell generation.

The human and mouse GATA-6 genes utilize two promoters and two initiation codons

GATA-6 has been implicated in the regulation of myocardial differentiation during cardiogenesis. To determine how its expression is controlled, we have characterized the human and mouse genes. We have mapped their transcriptional start sites and demonstrate that two alternative promoters and 5' noncoding exons are utilized. Both transcript isoforms are expressed in the same tissue-specific and developmental stage-specific pattern, and their ratio appears similar wherever examined. The more upstream noncoding exon showed a substantial degree of homology between the two mammalian species, suggesting a conserved regulatory function. Moreover, in transfection assays we show that elements within this exon act to promote its transcription. Positive regulatory elements that effect transcription from the more downstream exon were not apparent in this assay, revealing a regulatory distinction between the two promoters. We also demonstrate alternative initiator codon usage in both the human and mouse GATA-6 genes. Both isoforms of the protein are synthesized in vitro regardless of which 5' noncoding exon is present in the RNA, although the larger protein has greater transcriptional activation potential in transfection assays. Thus, GATA-6 function in the cell is controlled by a complex interplay of transcriptional and translational regulation.

Gata2 and Gata3: novel markers for early embryonic polarity and for non-neural ectoderm in the chick embryo

We have investigated in detail the expression patterns of two Gata genes, cGata2 and cGata3, during early chick development. In addition to confirming previously described expression of these two genes in developing brain, kidney and blood islands, this study reveals several important novel expression domains during very early stages of development. cGata2 is expressed in the area opaca in pre-primitive streak stages, forming a gradient along the A-P axis (strongest anteriorly). Both genes are expressed strongly in the entire non-neural ectoderm from stage 4+, and neither is expressed in prospective neural plate at any stage. Unlike other previously described non-neural markers, neither gene is expressed in the dorsal neural tube. We also describe dynamic expression of cGata2 and cGata3 during eye, ear and gut development.

The Mouse GATA-2 Gene is Expressed in the Para-Aortic Splanchnopleura and Aorta-Gonads and Mesonephros Region

We previously reported that the mouse GATA-2 gene is regulated by two alternative promoters (Minegishi et al, J Biol Chem, 273:3625, 1998). Although the more proximal IG (general) promoter is active in almost all GATA-2–expressing cells, the distal IS (specific) promoter activity was selectively detected in hematopoietic tissues but not in other mesodermal tissues. We report here in vivo analysis of the GATA-2 locus and its regulatory characteristics in hematopoietic tissues of transgenic mice. Transgenes containing 6 or 7 kbp of sequence flanking the 5′ end of the IS first exon direct expression of β-galactosidase or green fluorescent protein (GFP) reporter genes specifically to the para-aortic splanchnopleura, aorta-gonads, and mesonephros (AGM) region, and in the neural tissues. In situ hybridization analysis showed that reporter gene expression specifically recapitulates the endogenous expression profile of GATA-2 in these tissues. The flk-1, CD34, c-kit, and CD45 antigens were identified in the GFP-positive cells from the AGM region and fetal liver, indicating that GATA-2 is expressed in immature hematopoietic cells. Deletion of 3.5 kbp from the 5′ end of the 6.0 kbp IS promoter construct, including one of the DNase I hypersensitive sites, completely abolished hematopoietic expression. These experiments describe an early developmental GATA-2 hematopoietic enhancer located between 6.0 and 2.5 kbp 5′ to the IS exon.

Polarised expression pattern of focal contact proteins in highly motile antigen presenting dendritic cells

Dendritic cells are professional antigen presenting cells that capture antigens and migrate to lymphoid tissues to elicit specific T cell responses. Here we used an in vitro differentiation system for generating highly motile dendritic cells from chicken bone marrow progenitors by employing the conditional v-Rel estrogen receptor (ER) fusion protein v-RelER. Molecular mechanisms of dendritic cell motility were investigated. Differentiation of v-relER progenitors into dendritic cells is associated with a reduction in cell-cell and cell-extracellular matrix interactions as cells acquire motility. We demonstrate that v-relER progenitors and dendritic cells express several adhesion receptors and components of adhesion complexes. Differentiation of v-relER cells was accompanied by downregulation of focal adhesion kinase (FAK), a key molecule of adhesion complexes, but ectopic FAK expression did not affect cell adhesion and motility. Interestingly, v-relER dendritic cells exhibit a polarised expression pattern of actin and vimentin, with actin being highly concentrated at the leading edge of the cells where lamellipodia are formed. FAK, paxillin and tyrosine phosphorylated proteins are found at both poles of the cell and colocalise with actin at the leading edge, while surface beta1 integrin is confined to the uropod at the rear. CD34(+)stem cell-derived human dendritic cells also exhibited an elongated bipolar morphology, mode of migration and a polarised pattern of actin-vimentin expression similar to v-relER dendritic cells.

Developmental competence of the gut endoderm: genetic potentiation by GATA and HNF3/fork head proteins

A long-standing problem in developmental biology has been to understand how the embryonic germ layers gain the competence to differentiate into distinct cell types. Genetic studies have shown that members of the GATA and HNF3/fork head transcription factor families are essential for the formation and differentiation of gut endoderm tissues in worms, flies, and mammals. Recent in vivo footprinting studies have shown that GATA and HNF3 binding sites in chromatin are occupied on a silent gene in endoderm that has the potential to be activated solely in that germ layer. These and other data indicate that these evolutionarily conserved factors help impart the competence of a gene to be activated in development, a phenomenon called genetic potentiation. The mechanistic implications of genetic potentiation and its general significance are discussed.

Increased expression of the RIalpha subunit of the cAMP-dependent protein kinase A is associated with advanced stage ovarian cancer

The primary element in the cAMP signal transduction pathway is the cAMP-dependent protein kinase (PKA). Expression of the RIalpha subunit of type I PKA is elevated in a variety of human tumours and cancer cell lines. The purpose of this study was to assess the prognostic importance of RIalpha expression in patients with ovarian cancer. We have evaluated the expression of RIalpha in a panel of human ovarian tumours (n = 40) and five human ovarian cancer cell lines using quantitative reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. The human ovarian cell lines OAW42 and OTN14 express high endogenous levels of RIalpha mRNA and protein (at significantly higher mRNA levels than high tissue expressors, P < 0.05). The ovarian cell line A2780 expresses low endogenous levels of RIalpha mRNA and protein (also at higher mRNA levels than low tissue expressors, P < 0.05). Quantitative RT-PCR revealed no significant difference in RIalpha mRNA expression between different ovarian histological subtypes in this study. No associations were found between RIalpha mRNA expression and differentiation state. RIalpha mRNA expression was significantly associated with tumour stage (P = 0.0036), and this remained significant in univariate analysis (P = 0.0002). A trend emerged between RIalpha mRNA expression levels and overall survival in univariate analysis (P = 0.051), however, by multivariate analysis, stage remained the major determinant of overall survival (P = 0.0001). This study indicates that in ovarian epithelial tumours high RIalpha mRNA expression is associated with advanced stage disease. RIalpha expression may be of predictive value in ovarian cancer and may be associated with dysfunctional signalling pathways in this cancer type.

Neuroadaptations in ionotropic and metabotropic glutamate receptor mRNA produced by cocaine treatment

The expression of glutamate receptor/subunit mRNAs was examined 3 weeks after discontinuing 1 week of daily injections of saline or cocaine. The level of mRNA for GluR1-4, NMDAR1, and mGluR5 receptors was measured with in situ hybridization and RT-PCR. In nucleus accumbens, acute cocaine treatment significantly reduced the mRNA level for GluR3, GluR4, and NMDAR1 subunits, whereas repeated cocaine reduced the level for GluR3 mRNA. Acute cocaine treatment also reduced the NMDAR1 mRNA level in dorsolateral striatum and ventral tegmental area. In prefrontal cortex, repeated cocaine treatment significantly increased the level of GluR2 mRNA. The GluR2 mRNA level was not changed by acute or repeated cocaine in any other brain regions examined. Repeated cocaine treatment also significantly increased mGluR5 mRNA levels in nucleus accumbens shell and dorsolateral striatum. Functional properties of the ionotropic glutamate receptors are determined by subunit composition. In addition, metabotropic glutamate receptors can modulate synaptic transmission and the response to stimulation of ionotropic receptors. Thus, the observed changes in levels of AMPA and NMDA receptor subunits and the mGluR5 metabotropic receptor may alter excitatory neurotransmission in the mesocorticolimbic dopamine system, which could play a significant role in the enduring biochemical and behavioral effects of cocaine.

Partial rescue of GATA-3 by yeast artificial chromosome transgenes

GATA-3 is essential for murine embryonic development, but elucidating the genetic controls over the complex temporal and tissue-specific transcriptional regulatory pattern of this transcription factor gene has been problematic. Here we report the isolation and characterization of two yeast artificial chromosomes (YACs) bearing the murine GATA-3 gene. Ordered deletions of both YACs show that they define a 1-megabase pair contig spanning the GATA-3 locus. We found that a 120-kb YAC transgene, including 35 kb of 5' as well as 60 kb of 3' flanking sequence, confers normal GATA-3 expression at sites not revealed previously through analysis of plasmid transgenic lines. However, even this 120-kb YAC does not contain sufficient information to recapitulate the complete GATA-3 expression program during embryogenesis. While not complete in its regulatory capacity, the YAC transgene is nonetheless able to complement several homozygous GATA-3 mutant phenotypes and thereby prolong embryonic life.

GATA transcription factors as potentiators of gut endoderm differentiation

Gene inactivation studies have shown that members of the GATA family of transcription factors are critical for endoderm differentiation in mice, flies and worms, yet how these proteins function in such a conserved developmental context has not been understood. We use in vivo footprinting of mouse embryonic endoderm cells to show that a DNA-binding site for GATA factors is occupied on a liver-specific, transcriptional enhancer of the serum albumin gene. GATA site occupancy occurs in gut endoderm cells at their pluripotent stage: the cells have the potential to initiate tissue development but they have not yet been committed to express albumin or other tissue-specific genes. The GATA-4 isoform accounts for about half of the nuclear GATA-factor-binding activity in the endoderm. GATA site occupancy persists during hepatic development and is necessary for the activity of albumin gene enhancer. Thus, GATA factors in the endoderm are among the first to bind essential regulatory sites in chromatin. Binding occurs prior to activation of gene expression, changes in cell morphology or functional commitment that would indicate differentiation. We suggest that GATA factors at target sites in chromatin may generally help potentiate gene expression and tissue specification in metazoan endoderm development.

Alternate promoters and developmental modulation of expression of the chicken GATA-2 gene in hematopoietic progenitor cells

We have isolated and characterized the chicken GATA-2 (cGATA-2) gene. We show that, as in the case of some other members of the GATA gene family, the gene is expressed from alternative first exons. One of the resulting mRNAs represents only a minor form of the GATA-2 mRNA in the cells and tissues we analyzed; the other is ubiquitously expressed. We have defined the minimal promoter that controls expression of this most abundant mRNA and that is necessary for full activity in hematopoietic progenitor cells. The activity of this promoter in transient assays is consistent with developmental differences of expression levels in these cells. We identify within the promoter a previously unrecognized extended CCAAT motif essential for its activity. The organization of the cGATA-2 gene, with alternative first exons and a CCAAT box in the proximal promoter, is similar to that recently described for mouse GATA-2, and the proximal promoter also resembles the only promoter so far described in Xenopus. Nonetheless, the roles of the promoters in development and tissue-specific expression are quite different in these organisms, most strikingly in the mouse, which assigns developmental roles to its proximal and distal promoters that are quite different from those in the chicken. We suggest that although the overall organization may remain the same, the role assigned to each promoter varies among organisms. We identify distant upstream regulatory elements in the cGATA-2 gene that modulate expression from the proximal promoter and that may be responsible for this variation.

Role of GATA-1 in Proliferation and Differentiation of Definitive Erythroid and Megakaryocytic Cells In Vivo

To elucidate the contributions of GATA-1 to definitive hematopoiesis in vivo, we have examined adult mice that were rendered genetically defective in GATA-1 synthesis (Takahashi et al, J Biol Chem272:12611, 1997). Because the GATA-1 gene is located on the X chromosome, which is randomly inactivated in every cell, heterozygous females can bear either an active wild-type or mutant (referred to asGATA-1.05) GATA-1 allele, consequently leading to variable anemic severity. These heterozygous mutant mice usually developed normally, but they began to die after 5 months. These affected animals displayed marked splenomegaly, anemia, and thrombocytopenia. Proerythroblasts and megakaryocytes massively accumulated in the spleens of the heterozygotes, and we showed that the neomycin resistance gene (which is the positive selection marker in ES cells) was expressed profusely in the abnormally abundant cells generated in the GATA-1.05 mutant females. We also observed hematopoiesis outside of the bone marrow in the affected mutant mice. These data suggest that a small number of GATA-1.05 mutant hematopoietic progenitor cells begin to proliferate vigorously during early adulthood, but because the cells are unable to terminally differentiate, this leads to progenitor proliferation in the spleen and consequently death. Thus, GATA-1 plays important in vivo roles for directing definitive hematopoietic progenitors to differentiate along both the erythroid and megakaryocytic pathways. The GATA-1 heterozygous mutant mouse shows a phenotype that is analogous to human myelodysplastic syndrome and thus may serve as a useful model for this disorder.

Role of GATA-1 in Proliferation and Differentiation of Definitive Erythroid and Megakaryocytic Cells In Vivo

To elucidate the contributions of GATA-1 to definitive hematopoiesis in vivo, we have examined adult mice that were rendered genetically defective in GATA-1 synthesis (Takahashi et al, J Biol Chem272:12611, 1997). Because the GATA-1 gene is located on the X chromosome, which is randomly inactivated in every cell, heterozygous females can bear either an active wild-type or mutant (referred to asGATA-1.05) GATA-1 allele, consequently leading to variable anemic severity. These heterozygous mutant mice usually developed normally, but they began to die after 5 months. These affected animals displayed marked splenomegaly, anemia, and thrombocytopenia. Proerythroblasts and megakaryocytes massively accumulated in the spleens of the heterozygotes, and we showed that the neomycin resistance gene (which is the positive selection marker in ES cells) was expressed profusely in the abnormally abundant cells generated in the GATA-1.05 mutant females. We also observed hematopoiesis outside of the bone marrow in the affected mutant mice. These data suggest that a small number of GATA-1.05 mutant hematopoietic progenitor cells begin to proliferate vigorously during early adulthood, but because the cells are unable to terminally differentiate, this leads to progenitor proliferation in the spleen and consequently death. Thus, GATA-1 plays important in vivo roles for directing definitive hematopoietic progenitors to differentiate along both the erythroid and megakaryocytic pathways. The GATA-1 heterozygous mutant mouse shows a phenotype that is analogous to human myelodysplastic syndrome and thus may serve as a useful model for this disorder.

Multiple factors interacting at the GATA sites of the gonadotropin-releasing hormone neuron-specific enhancer regulate gene expression

Neuron-specific expression of the GnRH gene is dependent on an upstream multicomponent enhancer. This enhancer is functional in a small population of GnRH-producing hypothalamic neurons which, through the secretion of GnRH, mediates central nervous system control of reproductive function. GnRH enhancer function requires activation by the GATA family of transcription factors that act through tandem consensus GATA-binding motifs, GATA-A and GATA-B. Here we show that two newly identified DNA-binding factors, termed GBF-A1/A2 and GBF-B1, bind the GnRH enhancer at sites overlapping the GATA factor-binding motifs. In vitro bindings of GATA, GBF-A1/A2, and GBF-B1 to the GnRH enhancer sequences are independent. Specific mutation of either the consensus GATA motif or the GBF-B1 site of GATA-B does not alter binding of the overlapping factor in vitro. Utilizing a GnRH-expressing neuronal cell line as a model system, we show by transient transfection that GBF-B1 is necessary for enhancer activity and independently activates the GnRH promoter. Transactivation of the GnRH enhancer in GT1 cells and in NIH 3T3 cells by GATA-4 is modulated by GBF-B1 binding, suggesting GBF-B1 interferes with GATA factor binding through a steric mechanism.

Fibronectin binding promotes a PKC-dependent modulation of NF-kappa B in human T cells

NF-kappa B was identified as one of the transcription factors leading to antigen-independent stimulation through activation of integrin receptors. This effect was dependent upon stimulation of alpha 4 beta 1 and alpha 5 beta 1 integrins, the major fibronectin-binding integrins of Jurkat T cells, since either RGD or CS-1 peptides at 10(-4) M could prevent NF-kappa B activation. At variance with fibroblasts and smooth muscle cells, in which only p50 and p65 components of the NF-kappa B complex are induced, adhesion of T cells to fibronectin resulted in a strong upregulation of p50 and c-Rel and in a partial increase in p65 activity. The upregulation of NF-kappa B activity was abrogated by calphostin C, an inhibitor of protein kinase C. Cell adhesion determined a strong reduction in the cytoplasmic levels of the NF-kappa B inhibitor I kappa B alpha, reduction that was prevented after treatment with calphostin C, suggesting that PKC-dependent I kappa B alpha phosphorylation might be involved in the upregulation of NF-kappa B.

Blood-borne seeding by hematopoietic and endothelial precursors from the allantois

Until now the allantois has not been considered as a hematopoietic organ. Here we report experimental evidence demonstrating the in situ emergence of both hematopoietic and endothelial precursors in the avian allantoic bud. When the prevascularized allantoic bud from a quail embryo was grafted in the coelom of a chicken host, hematopoietic and endothelial cells later were found in the bone marrow of the host. Because the graft was located at a distance from the limb bud, these cells could reach the bone marrow only by the circulatory pathway. This blood-borne seeding may be accomplished by distinct hematopoietic and endothelial precursors, or by hemangioblasts, the postulated common precursors of these two lineages; we consider the latter interpretation more likely. We also show by reverse transcription-PCR that the allantois region expresses very early the GATA genes involved in hematopoiesis and some beta-globin chain genes.

Differential roles of GATA-1 and GATA-2 in growth and differentiation of mast cells

BACKGROUND

While mast cells have been previously shown to express both GATA-1 and GATA-2 mRNAs, individual functions for these related factors during their course of differentiation within the mast cell lineage have not yet been defined. To address this question, the expression of GATA-1 and GATA-2 mRNAs and proteins were examined in three mouse mast cell progenitor lines as well as in mast cells isolated from both wild-type and GATA-1-deficient mice.

RESULTS

Both mast cell progenitor lines, as well as primary mouse bone marrow-derived mast cells (BMMCs) and peritoneal mast cells (PMCs) were examined by RNA blotting and immunological analyses. GATA-2 protein was abundantly expressed in all three mast cell lines and in BMMCs, but only weakly in some of PMCs. In contrast, GATA-1 protein was expressed in PMCs and BMMCs after culture in the presence of IL3 and SCF. We also found the presence of Alcian blue staining-positive but berberine staining-negative mast cells in the skin of mice heterozygous to GATA-1 knock-down allele.

CONCLUSION

These results suggest that the expression of GATA factor-dependent genes is regulated by GATA-2 during mast cell development and that GATA-1 is required for the specification of differentiated mast cell phenotypes.

Paraffin-embedded tissue as a source of RNA for gene expression analysis in oral malignancy

OBJECTIVE

To assess the feasibility of using archival oral mucosal tissue to examine gene expression at the ribonucleic acid (RNA) level.

MATERIALS AND METHODS

We describe the isolation of RNA from 8 microns sections of formalin-fixed paraffin-embedded oral mucosal tissue. RNA was reverse transcribed and three candidate genes amplified by polymerase chain reaction (PCR). The ribosomal protein S14 gene is a housekeeping gene which has been used as an internal standard in several quantitative PCR protocols. The thymidine kinase (TK) gene is expressed at low levels in most tissues and, with a well-documented genomic organisation, is a useful tool for discrimination between genomic DNA and cDNA. The RI alpha gene is reported to be overexpressed in many cancer cell lines, in malignant tissue and in vitro transformed cells.

RESULTS

The S14 gene, the TK gene and the RI alpha gene of the cAMP-dependent protein kinase (PKA) were amplified successfully from formalin-fixed paraffin-embedded tissue sections. The TK primer pair is a useful additional tool in the unambiguous identification of RNA-derived species.

CONCLUSION

RNA suitable for reverse transcribed (RT)-PCR was extracted from archival oral mucosal tissue. This should permit rapid sequence analysis of transcribed tumor suppressor genes and oncogenes in this material. Furthermore, the RT-PCR approach described may allow quantification of gene expression in oral mucosal archival material processed in a standard fashion.

Structure and erythroid cell-restricted expression of a chicken cDNA encoding a novel zinc finger protein of the Cys + His class

We report the cloning, sequence analysis and expression pattern of chGfi, a zinc finger protein (Zfp)-encoding cDNA that was isolated from a cDNA library constructed with RNA from avian erythroblastosis virus (AEV)-transformed primary chicken erythroblasts. The 1387-bp-long chGfi cDNA encodes a full-length 337-amino-acid (aa) protein that contains six zinc fingers (Zf) of the 2Cys + 2His class at its C-terminus. Immunoblotting experiments with extracts from bone marrow cells detected a 38-kDa protein that corresponds to the M(r) of 38,690 calculated for the protein deduced from chGfi. The chGfi protein is most homologous to the rat Gfi-1 showing a sequence similarity of 92% over the Zf region and only two exchanges within the N-terminal 19 aa that constitute the Gfi-1 repressor domain. Expression of chGfi is only detected in transformed primary erythroblasts, in erythroid cells of the primitive and definitive lineage and in bone marrow cells. chGfi activity does not vary significantly during differentiation of transformed primary erythroblasts of the definitive lineage. No chGfi expression is detected in cells of the myeloid and lymphoid lineages or in a total of nine different organs of adult origin. Our results indicate that chGfi expression is restricted to erythroid cells of the primitive and definitive lineage.

Temporal and spatial control of murine GATA-3 transcription by promoter-proximal regulatory elements

GATA-3 is expressed in a temporally dynamic manner and fulfills vital functions during vertebrate fetal development. Homozygous mGATA-3 mutant embryos die at midgestation, thus complicating the analysis of its contribution to the development of specific cell fates in the many tissues where it is expressed during embryogenesis. We show here that the elements controlling GATA-3 regulation can be precisely refined, using transgenic mice, to discrete cis-acting domains: within 6 kb surrounding the transcriptional initiation site, separate sequences were found to control the expression of mGATA-3 in early muscle masses, in a subset of PNS neurons, in the genital tubercle, and in the branchial arches. The branchial arch regulatory element is particularly robust and was refined to a discrete enhancer sequence lying between nt -2832 and -2462 from the transcription initiation site. The enhancer contains potential binding sites for many well-characterized transcription factors, suggesting that mGATA-3 transcriptional activity may be regulated by these proteins (or related family members) in the mesenchyme of the arches that contribute to formation of the jaw. These studies show that discrete regulatory elements required for the elaboration of complex developmental programs can be individually localized, suggesting that the developmentally transient expression of individual transcription factors collaboratively contributes to the temporal and spatial pattern of cellular differentiation leading to the formation of adult anatomy.

Initiation of Murine Embryonic Erythropoiesis: A Spatial Analysis

Hematopoiesis in the mouse conceptus begins in the visceral yolk (VYS), with primitive erythroblasts first evident in blood islands at the headfold stage (E8.0). VYS erythropoiesis is decreased or abrogated by targeted disruption of the hematopoietic transcription factors tal-1, rbtn2, GATA-1, and GATA-2. To better understand the potential roles of these genes, and to trace the initial temporal and spatial development of mammalian embryonic hematopoiesis, we examined their expression patterns, and that of βH1-globin, in normal mouse conceptuses by means of in situ hybridization. Attention was focused on the 36-hour period from mid-primitive streak to early somite stages (E7.25 to E8.5), when the conceptus undergoes rapid morphologic changes with formation of the yolk sac and blood islands. Each of these genes was expressed in extraembryonic mesoderm, from which blood islands are derived. This VYS expression occurred in a defined temporal sequence: tal-1 and rbtn2 transcripts were detected earlier than the others, followed by GATA-2 and GATA-1, and then by βH1-globin. Transcripts for all of these genes were present in VYS mesoderm cell masses at the neural plate stage (E7.5), indicating commitment of these cells to the erythroid lineage before the appearance of morphologically recognizable erythroblasts. By early somite stages (E8.5), GATA-2 mRNA expression is downregulated in VYS blood islands as terminal primitive erythroid differentiation proceeds. We conclude that primitive mammalian erythropoiesis arises during gastrulation through the ordered temporal expression of tal-1, rbtn2, GATA2, and GATA-1 in a subset of extraembryonic mesoderm cells. During the stages analyzed, tal-1 and rbtn2 expression was also present in posterior embryonic mesoderm, while GATA-1 and GATA-2 expression was evident in extraembryonic tissues of ectodermal origin.