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Divergent regulation of vascular endothelial growth factor and of erythropoietin gene expression in vivo.

There is accumulating evidence from in vitro experiments that the gene expression of the vascular endothelial growth factor (VEGF) is, like that of the erythropoietin (EPO) gene, regulated by the oxygen tension and by divalent cations such as cobalt. Since the information about the regulation of VEGF gene expression in vivo is rather scarce, this study aimed to examine the influence of hypoxia and of cobalt on VEGF gene expression in different rat organs and to compare it with that on EPO gene expression. To this end male Sprague-Dawley rats were exposed to carbon monoxide (0.1% CO), hypoxia (8% O2 ) or to cobalt chloride (12 and 60 mg/kg s.c.) for 6 h. mRNA levels for VEGF- 188, -164, and -120 amino acid isoforms in lungs, hearts, kidneys and livers were semiquantitated by RNase protection. For these organs we found a rank order of VEGF mRNA abundance of lung >> heart > kidney = liver. EPO mRNA levels were semiquantitated in kidneys and livers. Hypoxia, CO and cobalt increased EPO mRNA levels 60-fold, 140-fold and 5-fold, respectively, in the kidneys, and 11-fold, 11-fold and 3-fold, respectively, in the livers. None of these manoeuvres caused significant changes of VEGF mRNA in lung, heart or kidneys. Only in the livers did hypoxia lead to a significant (50%) increase of VEGF mRNA. These findings suggest that, in contrast to the in vitro situation, the expression of the VEGF gene in normal rat tissues is rather insensitive to hypoxia. In consequence, the in vivo regulation of the VEGF and the EPO genes appear to differ substantially, suggesting that the regulation of the VEGF and EPO genes may not follow the same essential mechanisms in vivo.

Animals↗

cea5, a structurally divergent member of the murine carcinoembryonic antigen gene family, is exclusively expressed during early placental development in trophoblast giant cells.

The carcinoembryonic antigen (CEA) gene family encodes a large family of glycoproteins. Some are probably involved in the homeostasis/development of epithelial cells and granulocyte activation, while others e.g. the pregnancy-specific glycoproteins, are expressed in the placenta and are essential for a positive outcome of pregnancy. In this paper, we have characterized cea5, a member of the murine CEA gene family. RNase protection and in situ hybridization analyses revealed that Cea5 mRNA is exclusively synthesized in primary and secondary trophoblast giant cells of the placenta only during early stages of development. Full-length Cea5 cDNA was obtained by a reverse transcription-polymerase chain reaction using day 10.5 post-coitum placental RNA. The 1.6-kilobase pair (kb) Cea5 mRNA encodes a secreted glycoprotein with a predicted size of 30 kDa. It is composed of a leader peptide (L), one immunoglobulin (Ig) variable or N, and one Ig constant-like or A domain. This domain organization is unique within the human and murine CEA families. Two overlapping cosmid clones covering 54 kb of the cea5 gene locus were mapped. cea5 consists of three exons (L, N, A/3'-untranslated region exon) located within a 4-kb region. rnCGM2, the rat cea5 counterpart, exhibits the same restricted expression pattern. This together with their exceptional conservation within the rat and murine CEA families and their absence from the human CEA family suggests that cea5 and rnCGM2 are of functional importance for rodent placental development.

Amino Acid Sequence↗

Tissue-specific expression of beta-galactoside alpha-2,6-sialyltransferase. Transcript heterogeneity predicts a divergent polypeptide.

The beta-galactoside alpha-2,6-sialyltransferase represents a member of a family of sialyltransferases which catalyze the terminal addition of sialic acid to maturing carbohydrate chains. We surveyed rat tissues using cDNA probes complementary to coding and noncoding domains of the rat liver alpha-2,6-sialyltransferase. In addition to the expected differences in the level of sialyltransferase mRNA among the tissues, there were dramatic qualitative differences as well. Hepatic sialyltransferase probes hybridize to mRNAs of varying size on Northern blots. A tissue-dependent pattern of expression of these transcripts is documented. Evidence is presented that the multiple transcripts are generated from a common gene sequence. At least one instance of alternate splicing in the generation of the kidney sialyltransferase transcripts is predicted by S1 nuclease analysis. We report the isolation of a rat kidney cDNA clone, RKA, that substantiates this tissue-specific alternate splicing event. The RKA insert, although less than full-length, apparently encodes a polypeptide divergent from the reported hepatic alpha-2,6-sialyltransferase (1). RNA blot analysis indicates that the RKA-type transcripts represent a significant proportion of sialyltransferase RNA in rat kidney. Another class of kidney cDNA clones, RKE, is colinear with the hepatic sialyltransferase sequence. RNA blots probed for the divergent and common regions suggest that complex processing pathways are operative in the tissue-specific expression of sialyltransferase mRNA.

Amino Acid Sequence↗

Expression patterns of a twist-related gene in embryos of the spider Achaearanea tepidariorum reveal divergent aspects of mesoderm development in the fly and spider.

We cloned an Achaearanea tepidariorum (Chelicerata, Arachnida) gene related to Drosophila twist (twi), which encodes a basic helix-loop-helix transcription factor required to specify mesoderm fate in the Drosophila embryo. The cloned spider gene was designated At.twist (At.twi). We examined its expression by whole-mount in situ hybridization. At.twi transcripts were first detected in cells located at the polar and equatorial areas of the spherical embryo when the cumulus reached the equator. As the extra-embryonic area expanded, more cells expressed At.twi transcripts. The At.twi-expressing cells became distributed nearly uniformly in the embryonic area. At these stages, some At.twi-expressing cells were found in the surface epithelial cell layer, but other At.twi-expressing cells were at slightly deeper positions from the surface. When the embryo was transformed into a germ band, all At.twi-expressing cells were situated just beneath the surface ectoderm, where they became metamerically arranged. Although little expression was observed in the caudal lobe of the elongating germ band, new stripes of At.twi expression appeared beneath the ectoderm in accordance with the posterior growth. These observations suggested that the cells expressing At.twi were most likely mesoderm. We propose that At.twi can be used as a molecular marker for analyzing mesoderm development in the spider embryo. Moreover, comparison of the expression patterns of twi and At.twi revealed divergent aspects of mesoderm development in the fly and spider. In addition, we cloned an Achaearanea gene related to snail, which is another mesoderm-determining gene in Drosophila, and showed that its expression was restricted to the ectoderm with no indication for a role in mesoderm development.

Amino Acid Sequence↗

Compensatory responses of protein import and transcription factor expression in mitochondrial DNA defects.

Defects in mitochondrial DNA (mtDNA) evoke distinctive responses in the nuclear genome, leading to altered mitochondrial biogenesis. We used C(2)C(12) cells depleted of mtDNA (rho(-) cells) and fibroblasts from a mitochondrial encephalopathy, lactic acidosis, and strokelike episodes (MELAS) patient to examine adaptations of the protein import machinery and transcription factors involved in mitochondrial biogenesis. In rho(-) cells, Tom20 and Tim23 protein levels were reduced by 25% and 59%, whereas mtHSP70 was induced by twofold relative to control cells. These changes were accompanied by a 21% increase in enhanced yellow fluorescent protein (EYFP) import into mitochondria in rho(-) cells (P < 0.05). In contrast, in MELAS cells mtHSP70 was elevated by 70%, whereas Tom20 and Tom34 protein levels were increased by 45% and 112% relative to control values. EYFP import was not altered in MELAS cells. In rho(-) cells, protein levels of the transcription factors nuclear respiratory factor-1 (NRF-1) and transcription factor A (Tfam) declined by 33% and 54%, whereas no change was observed for the coactivator peroxisome proliferator receptor-gamma coactivator-1alpha (PGC-1alpha). In contrast, Tfam was increased by 40% in MELAS cells. Rho(-) cells displayed reduced oxygen consumption (Vo(2)) and ATP levels, along with a twofold increase in lactate levels (P < 0.05). In electrically stimulated C(2)C(12) cells, 109%, 78%, 60%, and 67% increases were observed in mtDNA, Vo(2), cytochrome-c oxidase (COX) activity, and Tom34 levels, respectively (P < 0.05). Our findings suggest that compensatory adaptations occurred to maintain normal rates of protein import in response to mtDNA defects and support a role for contractile activity in reducing pathophysiology associated with mtDNA depletion. Because the expression of nuclear-encoded transcription factors and protein import machinery components was dependent on the type of mtDNA defect, these findings suggest involvement of distinct signaling cascades, each dependent on the type of mitochondrial defect, resulting in divergent changes in nuclear gene expression patterns.

Animals↗

Divergent effects of oncostatin M on astroglioma cells: influence on cell proliferation, invasion, and expression of matrix metalloproteinases.

Oncostatin M (OSM), a cytokine of the interleukin-6 (IL-6) family, can either promote or inhibit cell growth in various normal and tumor cells. We addressed the effects of exogenous OSM on the proliferation and invasion of human astroglioma cells. In addition, we investigated one of the possible mechanisms involved: modulation of matrix metalloproteinase (MMP) expression and enzymatic activity. We found that OSM inhibited the proliferation of two human astroglioma cell lines (CH235-MG and U87-MG), and that this effect was not due to apoptosis. The inhibitory effect of OSM on proliferation was mediated through the gp130/OSMRbeta receptor complex. To extend these findings, we analyzed the effects of OSM on primary tumor cells from glioblastoma patients. OSM suppressed the proliferation of primary glioblastoma cells, but not that of normal astrocytes. Interestingly, OSM did not suppress astroglioma cell invasion. This may be due to the differential regulation of MMPs by OSM. We found that OSM inhibited the constitutive expression of MMP-2, while MMP-9 expression was enhanced in astroglioma cell lines. We conclude that OSM inhibits proliferation of human astroglioma cells and primary glioblastoma cells via the gp130/OSMRbeta receptor complex. However, OSM does not affect the invasive capacity of the astroglioma cells, which may be due to the divergent effects of OSM on MMP-2 and MMP-9 expression. Collectively, these findings suggest a complex role for OSM in astroglioma biology.

Annexin A5↗

Regulation of L-arginine transport and metabolism in vascular smooth muscle cells.

L-Arginine is a semi-essential amino acid that is metabolized to important regulatory molecules. L-Arginine is transported into vascular smooth muscle cells (SMC) by the cationic amino acid transporter (CAT) family of proteins where it is metabolized to nitric oxide (NO), polyamines, or L-proline. Inflammatory mediators, growth factors, and hemodynamic forces stimulate the transport of L-arginine in vascular SMC by inducing CAT gene expression. However, they exert highly specific and divergent regulatory effects on L-arginine metabolism. Inflammatory cytokines induce the expression of inducible NO synthase (iNOS) and direct the metabolism of L-arginine to the antiproliferative gas, NO. In contrast, growth factors stimulate the expression of arginase I and ornithine decarboxylase (ODC) and channel the metabolism of L-arginine to growth stimulatory polyamines. Alternatively, cyclic mechanical strain blocks both iNOS and ODC activity and stimulates arginase I gene expression, directing the metabolism of L-arginine to the formation of L-proline and collagen. Thus, specific biochemical and biophysical stimuli that are found in the circulation regulate the transport and metabolism of L-arginine in vascular SMC. The ability of these physiologically relevant stimuli to upregulate L-arginine transport and generate specific L-arginine metabolites modulates SMC function and may influence the development of vascular disease.

Animals↗

Bladder cancer outcome and subtype classification by gene expression.

Models of bladder tumor progression have suggested that genetic alterations may determine both phenotype and clinical course. We have applied expression microarray analysis to a divergent set of bladder tumors to further elucidate the course of disease progression and to classify tumors into more homogeneous and clinically relevant subgroups. cDNA microarrays containing 10,368 human gene elements were used to characterize the global gene expression patterns in 80 bladder tumors, 9 bladder cancer cell lines, and 3 normal bladder samples. Robust statistical approaches accounting for the multiple testing problem were used to identify differentially expressed genes. Unsupervised hierarchical clustering successfully separated the samples into two subgroups containing superficial (pT(a) and pT(1)) versus muscle-invasive (pT(2)-pT(4)) tumors. Supervised classification had a 90.5% success rate separating superficial from muscle-invasive tumors based on a limited subset of genes. Tumors could also be classified into transitional versus squamous subtypes (89% success rate) and good versus bad prognosis (78% success rate). The performance of our stage classifiers was confirmed in silico using data from an independent tumor set. Validation of differential expression was done using immunohistochemistry on tissue microarrays for cathepsin E, cyclin A2, and parathyroid hormone-related protein. Genes driving the separation between tumor subsets may prove to be important biomarkers for bladder cancer development and progression and eventually candidates for therapeutic targeting.

Aged↗

Relationship between Wnt-1 and En-2 expression domains during early development of normal and ectopic met-mesencephalon.

Grafting a met-mesencephalic portion of neural tube from a 9.5-day mouse embryo into the prosencephalon of a 2-day chick embryo results in the induction of chick En-2 (ChickEn) expression in cells in contact with the graft (Martinez et al., 1991). In this paper we investigate the possibility of Wnt-1 being one of the factors involved in En-2 induction. Since Wnt-1 and En-2 expression patterns have been described as diverging during development of the met-mesencephalic region, we first compared Wnt-1 and En-2 expression in this domain by in situ hybridization in mouse embryos after embryonic day 8.5. A ring of Wnt-1-expressing cells is detected encircling the neural tube in the met-mesencephalic region at least until day 12.5. This ring consistently overlapped with the En-2 expression domain, and corresponds to the position of this latter gene's maximal expression. We subsequently studied ChickEn ectopic induction in chick embryos grafted with various portions of met-mesencephalon. When the graft originated from the level of the Wnt-1-positive ring, ChickEn induction was observed in 71% of embryos, and in these cases correlated with Wnt-1 expression in the grafted tissue. In contrast, this percentage dropped significantly when the graft was taken from more rostral or caudal parts of the mesencephalic vesicle. Taken together, these results are compatible with a prolonged role of Wnt-1 in the specification and/or development of the met-mesencephalic region, and show that Wnt-1 could be directly or indirectly involved in the regulation of En-2 expression around the Wnt-1-positive ring during this time. We also provide data on the position of the Wnt-1-positive ring relative to anatomical boundaries in the neural tube, which suggest a more general role for the Wnt-1 protein as a positional signal involved in organizing the met-mesencephalic domain.

Animals↗

Brachyury (T) expression in embryos of a larvacean urochordate, Oikopleura dioica, and the ancestral role of T.

The Brachyury, or T, gene is required for notochord development in animals occupying all three chordate subphyla and probably also had this role in the last common ancestor of the chordate lineages. In two chordate subphyla (vertebrates and cephalochordates), T is also expressed during gastrulation in involuting endodermal and mesodermal cells, and in vertebrates at least, this expression domain is required for proper development. In the basally diverging chordate subphylum Urochordata, animals in the class Ascidiacea do not employ T during gastrulation in endodermal or nonaxial mesodermal cells, and it has been suggested that nonnotochordal roles for T were acquired in the cephalochordate-vertebrate lineage after it split with Urochordata. To test this hypothesis, we cloned T from Oikopleura dioica, a member of the urochordate class Appendicularia (or Larvacea), which diverged basally in the subphylum. Investigation of the expression pattern in developing Oikopleura embryos showed early expression in presumptive notochord precursor cells, in the notochord, and in parts of the developing gut and cells of the endodermal strand. We conclude that the ancestral role of T likely included expression in the developing gut and became necessary in chordates for construction of the notochord.

Amino Acid Sequence↗

Overlapping and distinct roles of the duplicated yeast transcription factors Ace2p and Swi5p.

The yeast transcription factors Ace2p and Swi5p regulate the expression of several target genes involved in mating type switching, exit from mitosis and cell wall function. We describe the analysis of 12 novel targets, some regulated by Ace2p or Swi5p alone and some by both. We show that Ace2p is the major regulator of four genes (CTS1, YHR143W, SCW11 and YER124C). Expression of all four is inhibited by Swi5p. Like Cts1p and Scw11p, the two new Ace2p targets are associated with cell wall metabolism. Yhr143p is localized to the cell wall, and deletion affects cell separation and enhances pseudohyphal growth. Deleting YER124C also affects cell separation and sensitivity to drugs targeted against the cell wall. Expression of PIR1, YPL158C and YNL046W is dependent on Swi5p alone. In contrast, expression of YBR158W, YNL078W and YOR264W is minimized when both ace2 and swi5 are disrupted. We propose that, although Ace2p and Swi5p co-operate to induce the expression of a subset of genes, some functional divergence has occurred. This results in a delay in the expression of those genes predominantly regulated by Ace2p, compared with those predominantly regulated by Swi5p.

Cell Cycle Proteins↗

IL-4 differentially regulates eotaxin and MCP-4 in lung epithelium and circulating mononuclear cells.

To investigate the mechanisms of eosinophil recruitment in allergic airway inflammation, we examined the effects of interleukin (IL)-4, a Th2-type cytokine, on eotaxin and monocyte chemoattractant protein-4 (MCP-4) expression in human peripheral blood mononuclear cells (PBMCs; n = 10), in human lower airway mononuclear cells (n = 5), in the human lung epithelial cell lines A549 and BEAS-2B, and in human cultured airway epithelial cells. IL-4 inhibited eotaxin and MCP-4 mRNA expression induced by IL-1 beta and tumor necrosis factor-alpha in PBMCs but did not significantly inhibit expression in epithelial cells. Eotaxin and MCP-4 mRNA expression was not significantly induced by proinflammatory cytokines in lower airway mononuclear cells. IL-1 beta-induced eotaxin and MCP-4 protein production was also inhibited by IL-4 in PBMCs, whereas IL-4 enhanced eotaxin protein production in A549 cells. In contrast, dexamethasone inhibited eotaxin and MCP-4 expression in both PBMCs and epithelial cells. The divergent effects of IL-4 on eotaxin and MCP-4 expression between PBMCs and epithelial cells may create chemokine concentration gradients between the subepithelial layer and the capillary spaces that may promote the recruitment of eosinophils to the airway in Th2-type responses.

Blotting, Northern↗

Transcriptional control of the citrate-inducible citMCDEFGRP operon, encoding genes involved in citrate fermentation in Leuconostoc paramesenteroides.

In this study we describe the expression pattern of the Leuconostoc paramesenteroides citMCDEFGRP operon in response to the addition of citrate to the growth medium. An 8.8-kb polycistronic transcript, which includes the citMCDEFGRP genes, was identified; its synthesis was dramatically induced upon addition of citrate to the growth medium. We also found that expression of the cit operon is subjected to posttranscriptional regulation, since processing sites included in four complex secondary structures (I, II, III, and IV) were identified by Northern blot analysis and mapped by primer extension. Upstream of the citMCDEFGRP operon a divergent open reading frame, whose expression was also increased by citrate, was identified by DNA sequencing and designated citI. The start and end sites of transcription of the cit operon and citI gene were mapped. The start sites are separated by a stretch of 188 bp with a very high A+T content of 77% and are preceded by transcriptional promoters. The end sites of the transcripts are located next to the 3' end of two secondary structures characteristic of rho-independent transcriptional terminators. The effect of the citI gene on expression of the cit operon was studied in Escherichia coli. The presence of the citI gene in cis and in trans resulted in increased activity of the cit promoter. These data provide the first evidence that citrate fermentation in Leuconostoc is regulated at the transcriptional level by a transcriptional activator rather than by a repressor.

Bacterial Proteins↗

Structure, spatial, and temporal expression of two sea urchin metallothionein genes, SpMTB1 and SpMTA.

The metallothionein-B genes of the sea urchin Strongylocentrotus purpuratus encode a metallothionein (MT) isoform distinguishable from the MTA isoform. The MTB subfamily consists of at least two genes, MTB1 and MTB2, and possibly two to three others. The unique MTB1 and MTA genes have a high degree of identity but diverge in structural detail and expression. Transcripts of the MTA, MTB1, troponin C Spec 1, and CyIIIa actin genes begin simultaneously to accumulate at an early blastula stage. MTB1 mRNA becomes localized in the embryonic gut and oral ectoderm, whereas MTA, Spec 1, and CyIIIa actin mRNAs are spatially restricted to the aboral ectoderm. Several DNA elements are localized at the same positions in the MTB1 and MTA genes: these include respective CATA and TATA boxes, two metal response elements, and three distinct upstream DNA elements that are also present, and in the same order, in the Spec 1 gene promoter. A heptameric sequence, element A, is present at two sites each in the Spec 1 and CyIIIa actin genes, five sites in MTA, but only one site in MTB1. Most strikingly, the first intron of MTA contains elements not found in the MTB1 introns, including a consensus metal response element, an element A, and the P3A site demonstrated in the CyIIIa actin gene to be linked to the regulation of spatial expression.

Amino Acid Sequence↗

DO beta: a new beta chain gene in HLA-D with a distinct regulation of expression.

The HLA-D region of the human major histocompatibility complex encodes the genes for the alpha and beta chains of the DP, DQ and DR class II antigens. A cDNA clone encoding a new class II beta chain (designated DO) was isolated from a library constructed from mRNA of a mutant B-cell line having a single HLA haplotype. Complete cDNA clones encoding the four isotypic beta chains of the DR1, DQw1, DPw2 and putative DO antigens were sequenced. The DO beta gene was mapped in the D region by hybridization with DNA of HLA-deletion mutants. DO beta mRNA expression is low in B-cell lines but remains in mutant lines which have lost expression of other class II genes. Unlike other class II genes DO beta is not induced by gamma-interferon in fibroblast lines. The DO beta gene is distinct from the DP beta, DQ beta and DR beta genes in its pattern of nucleotide divergence. The independent evolution and expression of DO beta suggest that it may be part of a functionally distinct class II molecule.

Amino Acid Sequence↗

Similar and divergent patterns in the regulation of matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of MMP-1 gene expression in benign and malignant human thyroid cells.

An imbalance between the activity of matrix metalloproteinases (MMPs) (proteolytic enzymes that degrade protein components of the extracellular matrix) and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), may be one of the mechanisms responsible for tumor cell invasion. We have investigated the regulation of MMP-1 and TIMP-1 gene expression in benign and malignant (follicular, anaplastic, and papillary) human thyroid cells. As expected of cells with invasive potential, detectable MMP-1 messenger RNA (mRNA) levels were observed in malignant cells under basal conditions, in contrast to undetectable levels in benign cells. Exposure of these cells, for 1 h, to the active phorbol ester, phorbol 12-myristate 13-acetate (TPA, 100 nmol/L), acting via protein kinase C (PKC), elicited an increase in MMP-1 mRNA, with a peak stimulation after a 3- to 4-h culture period. Epidermal growth factor (EGF, 25 ng/mL), however, acting via protein tyrosine kinase (PTK), stimulated such gene expression in malignant cells but failed to do so in benign cells. TIMP-1 mRNA was not significantly altered by the TPA-PKC, EGF-PTK, or TSH-protein kinase A (PKA) pathways in malignant cells. In benign cells, however, TPA induced a small, though significant, increase in TIMP-1. The MMP-1 stimulation by EGF and lack of TPA-induced rise in TIMP-1 in malignant cells, in sharp contrast to the effects obtained in benign thyrocytes, seems to indicate that the MMP: TIMP balance favors a more extensive extracellular matrix protein breakdown by malignant thyrocytes, as expected of cells exhibiting invasive capacity. TSH (10-500 microU/mL) failed to significantly influence basal MMP-1 or TIMP-1 mRNA levels, but it caused a dose-dependent inhibition in TPA- and EGF-induced MMP-1 mRNA in malignant cells, and TPA-stimulated MMP-1 and TIMP-1 in benign cells. The repressive action of TSH on MMP-1 mRNA was mimicked by forskolin and 8-bromo-cAMP and was abrogated by the PKA inhibitor, H-89, suggesting that the TSH inhibitory action is PKA-mediated. In conclusion, the present study provides novel data on MMP-1 and TIMP-1 gene expression and their modulation by the major signal transduction pathways operating in human thyroid cells. Similar and divergent patterns have emerged in the regulation of such gene expression in benign and malignant human thyrocytes, in many instances in accord with the concept of MMP playing the role of stimulating, and TIMP inhibiting, cell invasion. Although MMP-1 may be just one of the many factors responsible for tumor cell invasion, the present findings demonstrating the possibility, at least in vitro, of repressing MMP gene expression may have important clinical ramifications.

8-Bromo Cyclic Adenosine Monophosphate↗