Human Chorionic Cells Research Articles

Glycodelin-A modulates syncytialization of human BeWo choriocarcinoma cell line

Cytotrophoblasts are the key trophoblast cells which differentiate into different trophoblast lineages. In this report, glycodelin-A action on fusion of a cytotrophoblast-like cell line (BeWo) was investigated. It significantly reduced the spontaneous fusion of BeWo cells. The treatment enhanced the invasion and extracellular-signal regulated kinases activation of BeWo cells. The mRNA expression of syncytialization markers, human chorionic gonadotrophin and glial cells missing homolog 1 were suppressed upon glycodelin-A treatment. The data suggest a possible function of glycodelin-A in mediating cytotrophoblast differentiation.

Isolation and Characterization of Mesenchymal Stem Cells from Amniotic Fluid and Chorionic Villi

Isolation and Characterization of Mesenchymal Stem Cells from Amniotic Fluid and Chorionic Villi

A Role for Nuclear Factor Interleukin-3 (NFIL3), a Critical Transcriptional Repressor, in Down-Regulation of Periovulatory Gene Expression.

The LH surge triggers dramatic transcriptional changes in genes associated with ovulation and luteinization. The present study investigated the spatiotemporal expression of nuclear factor IL-3 (NFIL3), a transcriptional regulator of the basic leucine zipper transcription factor superfamily, and its potential role in the ovary during the periovulatory period. Immature female rats were injected with pregnant mare's serum gonadotropin, treated with human chorionic gonadotropin (hCG), and ovaries or granulosa cells were collected at various times after hCG. Nfil3 mRNA was highly induced both in intact ovaries and granulosa cells after hCG treatment. In situ hybridization demonstrated that Nfil3 mRNA was highly induced in theca-interstitial cells at 4–8 h after hCG, localized to granulosa cells at 12 h, and decreased at 24 h. Overexpression of NFIL3 in granulosa cells inhibited the induction of prostaglandin-endoperoxide synthase 2 (Ptgs2), progesterone receptor (Pgr), epiregulin (Ereg), and amphiregulin (Areg) and down-regulated levels of prostaglandin E2. The inhibitory effect on Ptgs2 induction was reversed by NFIL3 small interfering RNA treatment. In theca-interstitial cells the expression of hydroxyprostaglandin dehydrogenase 15-(nicotinamide adenine dinucleotide) (Hpgd) was also inhibited by NFIL3 overexpression. Data from luciferase assays demonstrated that NFIL3 overexpression decreased the induction of the Ptgs2 and Areg promoter activity. EMSA and chromatin immunoprecipitation analyses indicated that NFIL3 binds to the promoter region containing the DNA-binding sites of cAMP response element binding protein and CCAAT enhancer binding protein-β. In summary, hCG induction of NFIL3 expression may modulate the process of ovulation and theca-interstitial and granulosa cell differentiation by regulating expression of PTGS2, PGR, AREG, EREG, and HPGD, potentially through interactions with cAMP response element binding protein and CCAAT enhancer binding protein-β on their target gene promoters.

Tumor Necrosis Factor Stimulates Matrix Metalloproteinase 9 Secretion from Cultured Human Chorionic Trophoblast Cells Through TNF Receptor 1 Signaling to IKBKB-NFKB and MAPK1/3 Pathway1

The identification of proinflammatory signal transduction pathways may suggest new therapeutic targets. In this study, we examine which signaling pathways are involved in tumor necrosis factor (TNF)-induced matrix metalloproteinase 9 (MMP9) secretion in human chorionic trophoblast (CT) cells. Purified CT cells were cultured in the presence of antibodies or chemical inhibitors that specifically block/inhibit distinct TNF receptors and kinase pathways. TNF-induced proMMP9 production, as measured by zymography, was significantly blocked/inhibited by TNF receptor 1 (TNFRSF1A) antibody, NFKB activation inhibitor (NFKBAI), and MAPK1/3 (ERK) inhibitor (U0126) (P < 0.01), but not by TNF receptor 2 (TNFRSF1B) antibody, MAPK14 (p38 MAPK) inhibitor (SB203580), and MAPK8/9/10 (JNK) inhibitor (SP600125). By Western blot analysis, we found that TNF rapidly and significantly increased phosphorylation of IKBKB, MAPK1/3, and MAPK8/9/10 and that the phosphorylation of these kinases by TNF was reduced significantly by TNFRSF1A neutralizing antibody, but not by TNFRSF1B neutralizing antibody. Moreover, we found that TNF increased TNF receptor-associated factor (TRAF) 1 and decreased TRAF2 protein expression through TNFRSF1A, but not TNFRSF1B. The CT cells that had increased TRAF1 and decreased TRAF2 after an initial TNF treatment demonstrated a dramatic deficiency in phosphorylation of the above protein kinases following a secondary TNF treatment. Localization of RELA subunit by immunocytochemistry was shifted to the nuclei after TNF treatment compared to cytosol in untreated controls. We also found cross-talk between the phosphoinositide 3-kinase pathway and ERK pathway. In summary, we have demonstrated that TNF stimulates proMMP9 production in CT cells through TNFRSF1A-TRAFs-IKBKB-NFKB and ERK signaling pathways, but not through TNFRSF1B and JNK/p38-AP-1 pathways.

Immunohistochemical Labeling of the Inhibin/Activin βC Subunit in Normal Human Placental Tissue and Chorionic Carcinoma Cell Lines

Inhibins and activins are important regulators of the female reproductive system. A novel inhibin subunit, named betaC, has been identified and demonstrated to be expressed in several human tissues. We demonstrate here that inhibin betaC is expressed in human placenta. Expression of the inhibin betaC subunit was demonstrated at the protein level by means of immunohistochemical evaluation and at the transcriptional level by an inhibin betaC-specific RT-PCR analysis. Expression of inhibin betaC was detected in the human chorionic carcinoma cell lines JEG and BeWo. Although the precise role of this novel inhibin subunit in human placenta development and homeostasis is unclear, analogies with other inhibin subunits and the strong expression of betaC in normal human trophoblast cells and chorionic carcinoma cells suggest that betaC may be involved in autocrine/paracrine signaling pathways, angiogenesis, decidualization, and tissue remodeling under normal and malignant conditions. Additionally, JEG and BeWo express betaC and, therefore, can be used as a cell culture model for further functional analysis of this subunit in the human placenta.

Human Placenta Is a Potent Hematopoietic Niche Containing Hematopoietic Stem and Progenitor Cells throughout Development

Hematopoietic stem cells (HSCs) are responsible for the life-long production of the blood system and are pivotal cells in hematologic transplantation therapies. During mouse and human development, the first HSCs are produced in the aorta-gonad-mesonephros region. Subsequent to this emergence, HSCs are found in other anatomical sites of the mouse conceptus. While the mouse placenta contains abundant HSCs at midgestation, little is known concerning whether HSCs or hematopoietic progenitors are present and supported in the human placenta during development. In this study we show, over a range of developmental times including term, that the human placenta contains hematopoietic progenitors and HSCs. Moreover, stromal cell lines generated from human placenta at several developmental time points are pericyte-like cells and support human hematopoiesis. Immunostaining of placenta sections during development localizes hematopoietic cells in close contact with pericytes/perivascular cells. Thus, the human placenta is a potent hematopoietic niche throughout development.

Interphase FISH Demonstrates that Human Adipose Stromal Cells Maintain a High Level of Genomic Stability in Long-Term Culture

Human adipose stromal cells (ASCs) reside within the stromal-vascular fraction (SVF) in fat tissue, can be readily isolated, and include stem-like cells that may be useful for therapy. An important consideration for clinical application and functional studies of stem/progenitor cells is their capacity to maintain chromosome stability in culture. In this study, cultured ASC populations and ASC clones were evaluated at intervals for maintenance of chromosome stability. Uncultured SVF (uSVF) cells were included for comparison. G-banded chromosome analysis demonstrated that ASCs are diploid and have a normal karyotype. However since only approximately 20 cells are examined, low levels of chromosome instability would not be detected. To increase detection sensitivity, fluorescence in situ hybridization was employed, to permit chromosome enumeration in larger numbers of interphase cells. Seven cultured ASC populations, two ASC clones and four uSVF samples were examined. Chromosome X and 17 probes identified diploid, tetraploid, and aneuploid interphase cells. Both cultured ASC populations [up to approximately 35 Population Doublings (PDs)] and uSVF cells exhibited a similar level of diploidy (97.8% n = 6,355 and 98.83% n = 1,197, respectively) and numerical abnormalities, suggesting that cultured ASCs are genomically stable and supporting their suitability for transplantation applications. In comparison, cultured primary human chorionic villus cells exhibited marked genomic instability resulting in an 11.6% tetraploidy rate after 8-10 PD. Thus effects of culture on genomic stability may be cell type dependent and should be tested by appropriately scaled interphase fluorescence in situ hybridization analysis in any ex vivo expanded cell population destined for transplantation.

The metastasis-associated genes MTA1 and MTA3 are abundantly expressed in human placenta and chorionic carcinoma cells

Normal placenta development relies on the ability of trophoblast cells to invade into the uterus and to build up an extensively vascularized feto-maternal tissue, necessary for the nutrition of the embryo. The ability of cell migration, invasion, and the ability to induce neovascularization are likewise hallmarks of cancer cells. The metastasis-associated genes MTA1 and MTA3 are known to be involved in cancer cell migration by regulation of cell adhesion proteins and to induce the expression of neoangiogenic cytokines, as recently shown by us for ovarian cancer cells. Therefore, we analyzed the expression of MTA1 and MTA3 in normal human placenta tissues and the chorionic cancer cell lines BeWo, JEG, and JAR. Immunohistochemical analysis revealed a rather strong expression of MTA1 and MTA3 in the nuclei of human trophoblast cells. A high expression level of MTA1 and MTA3 was further observed in the nuclei of human chorionic carcinoma cells, as shown by immunofluorescence analysis, and confirmed by Western blot and RT-PCR analysis. We conclude that the high expression level of MTA proteins in human chorionic cells might facilitate trophoblast cell migration and neoangiogenesis, and might further predispose human chorionic cancer cells with properties that are characteristic for this highly aggressive and metastatic carcinoma type.

Lactate Dehydrogenase Leakage as a Marker for Apoptotic Cell Degradation Induced by Influenza Virus Infection in Human Fetal Membrane Cells

Objective: In order to elucidate the implication of apoptosis in lactate dehydrogenase (LDH) leakage from influenza virus-infected cells, the effects of a general caspase inhibitor, N-t-Boc-Asp(OMe)-fluoromethylketone (Boc-D-fmk), on LDH leakage, apoptosis induction and virus proliferation were examined. Methods: Cultured human fetal membrane chorion and amnion cells were incubated with or without Boc-D-fmk after influenza virus infection. LDH leakage was estimated by measuring LDH activities in the culture supernatants and cell lysates. The extent of apoptosis was determined by caspase-3 protein cleavage and DNA fragmentation. Virus proliferation was determined by a plaque-forming assay. Results: While virus proliferation was observed in both chorion and amnion cells, the virus infection resulted in LDH leakage, caspase-3 protein cleavage, and oligonucleosomal DNA fragmentation, all of which were observed only in the chorion cells and inhibited by the presence of Boc-D-fmk except for the virus proliferation. Conclusion: LDH level in amniotic fluid is known to be one of markers for predicting fetal membrane damage. Therefore, this study provides a possible diagnostic application of LDH level to predict the extent of tissue damage of fetal membranes via apoptosis induced by influenza virus infection.

Enhancement of Cortisol-Induced 11β-Hydroxysteroid dehydrogenase Type 1 Expression by Interleukin 1β in Cultured Human Chorionic Trophoblast Cells

Chorion is the most abundant site of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) expression within intrauterine tissues. It is important to study the regulation of 11beta-HSD1 expression in the chorion in terms of local cortisol production during pregnancy. Using real-time PCR and enzyme activity assay, we found that cortisol (1 mum) and IL-1beta (10 ng/ml) for 24 h significantly increased 11beta-HSD1 mRNA expression and reductase activity in cultured human chorionic trophoblasts. A further significant increase of 11beta-HSD1 mRNA expression and reductase activity was observed with cotreatment of cortisol and IL-1beta. To explore the mechanism of induction, 11beta-HSD1 promoter was cloned into pGL3 plasmid expressing a luciferase reporter gene. By transfecting the constructed vector into WISH cells, an amnion-derived cell line, we found that cortisol (1 microM) or IL-1beta (10 ng/ml) significantly increased reporter gene expression. Likewise, an additional increase in reporter gene expression was observed with cotreatment of cortisol and IL-beta. To explore the physiological significance of 11beta-HSD1 induction in the chorion, we studied the effect of cortisol on cytosolic phospholipase A(2) and cyclooxygenase 2 expression. We found that treatment of chorionic trophoblast cells with cortisol (1 microM) induced both cytosolic phospholipase A(2) and cyclooxygenase 2 mRNA expression. We conclude that cortisol up-regulates 11beta-HSD1 expression through induction of promoter activity, and the effect was enhanced by IL-1beta, suggesting that more biologically active glucocorticoids could be generated in the fetal membranes in the presence of infection, which may consequently feed forward in up-regulation of prostaglandin synthesis.

Secretion of Bioactive Interleukin-6 and Tumor Necrosis Factor-α Proteins from Primary Cultured Human Fetal Membrane Chorion Cells Infected with Influenza Virus

Influenza virus infection during pregnancy is implicated in one of the causes of premature delivery, abortion and stillbirth. Pro-inflammatory cytokines, such as interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha produced by fetal membranes, are postulated to facilitate premature delivery. We investigated the secretion of IL-6 and TNF-alpha from primary cultured human fetal membrane chorion and amnion cells infected with influenza virus at protein and bioactivity levels in order to understand the pathology of premature delivery during influenza virus infection. Concentrations of IL-6 and TNF-alpha proteins were significantly increased in culture supernatants of chorion cells by influenza virus infection. Culture supernatants of the virus-infected chorion cells stimulated the proliferation of IL-6-sensitive 7-TD-1 cells and induced the cytolysis of TNF-alpha-sensitive L929 cells, both activities of which were inhibited by the addition of respective antibody, whereas no such phenomena were observed in amnion cells. The results demonstrated that only chorion cells secreted significant amounts of bioactive IL-6 and TNF-alpha proteins responding to influenza virus infection. The present study suggests a possibility that the secretion of bioactive IL-6 and TNF-alpha proteins from fetal membrane chorion cells is implicated in the pathogenesis of premature delivery during influenza virus infection.

Engraftment Potential of Human Amnion and Chorion Cells Derived from Term Placenta

Fetal membranes are tissues of particular interest for several reasons, including their role in preventing rejection of the fetus and their early embryologic origin. which may entail progenitor potential. The immunologic reactivity and the transplantation potential of amnion and chorion cells, however, remain to be elucidated. Amnion and chorion cells were isolated from human term placenta and characterized by immunohistochemistry, flow cytometric analysis, and expression profile of relevant genes. The immunomodulatory characteristics of these cells were studied in allogeneic and xenogeneic mixed lymphocyte reactions and their engraftment potential analyzed by transplantation into neonatal swine and rats. Posttransplant chimerism was determined by polymerase chain reaction analysis with probes specific for human DNA. Phenotypic and gene expression studies indicated mesenchymal stem cell-like profiles in both amnion and chorion cells that were positive for neuronal, pulmonary, adhesion, and migration markers. In addition, cells isolated both from amnion and chorion did not induce allogeneic nor xenogeneic lymphocyte proliferation responses and were able to actively suppress lymphocyte responsiveness. Transplantation in neonatal swine and rats resulted in human microchimerism in various organs and tissues. Human amnion and chorion cells from term placenta can successfully engraft neonatal swine and rats. These results may be explained by the peculiar immunologic characteristics and mesenchymal stem cell-like phenotype of these cells. These findings suggest that amnion and chorion cells may represent an advantageous source of progenitor cells with potential applications in a variety of cell therapy and transplantation procedures.

Trypanosoma cruzi: productive infection is not allowed by chorionic villous explant from normal human placenta in vitro

We hypothesize that a sustained infection of Trypanosoma cruzi into placental tissue might be diminished. Human placental chorionic villi and VERO cells as controls were co-cultured with T. cruzi. Parasites occupied 0.0137% at 3 h, 0.0224% (24 h), and 0.0572% (72 h) of the total chorionic villi area analyzed and some few placental samples were negative to parasite DNA, whereas 52% of VERO cells were infected at 3 h and parasites occupied 0.57%, at 24 h the parasite area was of 2.78% and at 72 h was of 3.32%. There were no live parasites in placenta— T. cruzi culture media at 72 h of co-culture. There were significantly increased dead parasites when T. cruzi was treated with unheated culture media coming from placental explants and fewer dead parasites when pre-heated culture media were employed. Conclusion Low productive infection by T. cruzi into placental tissue associated with no viable parasites in the culture media partially due to placental thermo labile substances.

Candidate cis-elements for human renin gene expression in the promoter region.

The regulation of renin gene expression, the rate-limiting enzyme of the system, is thought to be fundamental to the total system. Previously, we mapped six putative cis-elements in the promoter region of the human renin gene with nuclear proteins from human chorionic cells and human renal cortex by DNase I protection assay (footprint A-F). Each footprint contains Ets motif like site (A), HOXñPBX recognition sequence (B), unknown sequence as DNA binding consensus (C), CRE (D), COUP-TFII (ARP-1) motif like site (E), and AGE3 like site (F). Footprint D has been characterized by means of functional studies as the genuine human renin gene CRE interacting with CREB in cooperation with the site of footprint B. To obtain further clues to the specific expression in the promoter region, these putative cis-elements were conducted to a consensus-specific binding assay to compare renin-producing and non-renin-producing cells by EMSA and electromobility super-shift assay. Different sequence-specific DNA/protein binding was obtained among the different cell lines with footprint B site, with COUP-TFII (ARP-1) motif like site and possibly with footprint F site. The results implicate these putative cis-elements and each corresponding trans-factor in the specific expression of the human renin gene in the promoter region. Further functional characterization of these elements would provide important data for a better understanding of human renin gene expression.

Mechanism of cortisol/progesterone antagonism in the regulation of 15-hydroxyprostaglandin dehydrogenase activity and messenger ribonucleic acid levels in human chorion and placental trophoblast cells at term.

Prostaglandin dehydrogenase (PGDH) metabolizes prostaglandins (PGs) to render them inactive. We reported previously that cortisol (F) decreases and progesterone (P(4)) maintains PGDH activity/expression in human chorion and placenta. Furthermore, we have shown that F and P(4) compete for regulation of PGDH. We hypothesized that P(4) maintains PGDH activity through interaction with the glucocorticoid receptor (GR) and that elevations in F compete with P(4) at the GR, resulting in a decrease in PGDH at term. By immunohistochemistry and Western blotting analysis, we localized immunoreactive GR and progesterone receptor (PR) to chorion and placental trophoblast cells. We treated chorion and placental trophoblast cells in culture with F, dexamethasone (DEX), beta-methasone, P(4), trilostane (a 3 beta-hydroxysteroid dehydrogenase inhibitor), medroxyprogesterone acetate (MPA), and/or 21-hydroxy-6,19-oxidopregn-4-ene-3,20-dione (21OH-6OP; a GR antagonist). By RIA and Northern blotting analysis, all glucocorticoids (GCs) decreased PGDH activity/expression. Coincubation with 21OH-6OP reversed GC inhibition of PGDH; MPA, but not P(4), treatment stimulated PGDH activity. Trilostane inhibited PGDH activity, and coincubation with P(4) or MPA reversed trilostane inhibition of PGDH. Treatment with trilostane, P(4), 21OH-6OP, or MPA plus 21OH-6OP reversed P(4) and MPA up-regulation of PGDH activity. Our findings suggest that F inhibition and P(4) stimulation of PGDH may be mediated by PR, but also via the GR, in chorion and placenta.

Regulation of 15-hydroxy prostaglandin dehydrogenase by corticotrophin-releasing hormone through a calcium-dependent pathway in human chorion trophoblast cells.

Prostaglandins (PGs) play a crucial role in mediating parturition events, and their synthesis and metabolism are regulated by PG H synthase and 15-hydroxy-PG dehydrogenase (PGDH), respectively. Within the chorion tissue, it is the actions of PGDH that predominate. Throughout gestation, the fetal membranes secrete increasing amounts of CRH. We hypothesized that CRH, produced locally in the chorion, could act to modulate PGDH activity throughout gestation. To investigate this, we obtained Percoll-purified human chorion and placental trophoblast cells from uncomplicated term pregnancies and cultured them for 72 h. Activity of PGDH was assessed by incubation (4 h) with PGF(2alpha) (282 nM) and measurement of conversion to 13,14-dihydro-15-keto PG F(2alpha). Dose-response curves were constructed for the chorion cell cultures with CRH or 8-bromo-cAMP. To investigate the role of CRH and calcium, cells were treated with either astressin, a CRH antibody, BAPTA, or EGTA. CRH (0-1 micro M) had no effect on PGDH activity; however, cells treated with astressin (10 micro M), with or without exogenous CRH (1 micro M), and cells treated with a CRH antibody showed a significant decrease in PGDH activity. 8-Bromo-cAMP (0-1 mM) had no effect on 13,14-dihydro-15-keto PG F(2alpha) output in chorion trophoblast cells but significantly decreased output from placental trophoblast cells. Cells treated with either BAPTA-AM or EGTA had significantly reduced PGDH activity; and, at intermediate concentrations of chelator, exogenous CRH restored PGDH activity. We suggest that, in chorion trophoblast cells, endogenously produced CRH exerts a tonic stimulatory effect on PGDH activity and may help maintain a metabolic barrier, preventing the transfer of bioactive PGs from the chorioamnion to the myometrium.

Cortisol/Progesterone Antagonism in Regulation of 15-Hydroxysteroid Dehydrogenase Activity and mRNA Levels in Human Chorion and Placental Trophoblast Cells at Term

Cortisol/Progesterone Antagonism in Regulation of 15-Hydroxysteroid Dehydrogenase Activity and mRNA Levels in Human Chorion and Placental Trophoblast Cells at Term

Cortisol/progesterone antagonism in regulation of 15-hydroxysteroid dehydrogenase activity and mRNA levels in human chorion and placental trophoblast cells at term.

PGs mediate parturition events. 15-Hydroxyprostaglandin dehydrogenase (PGDH) catalyzes the first step in the metabolism of PGs to render them inactive. We have reported previously that cortisol (F) decreases PGDH activity and progesterone (P(4)) maintains PGDH in human chorion and placenta at term. To study the interaction of P(4) and F on the regulation of PGDH, we treated chorion and placental trophoblast cells in culture with combinations of F, dexamethasone, P(4), trilostane, and medroxyprogesterone acetate (MPA). Following a 24-h steroid treatment period and 4-h PGF(2alpha) challenge, culture media and cells were collected for measurement of PGF(2alpha) levels and PGDH mRNA by RIA and Northern blotting analysis. F and dexamethasone decreased PGDH activity and mRNA levels. Exogenous P(4) did not significantly alter PGDH activity or mRNA levels; however, MPA significantly stimulated PGDH activity. Trilostane decreased P(4) production by more than 90% and also decreased PGDH activity and expression. Coincubation with P(4) or MPA reversed trilostane inhibition of PGDH, consistent with a stimulatory role for endogenous P(4) on PGDH. MPA significantly reversed F inhibition of PGDH activity and mRNA levels. In the presence of trilostane, P(4) at equimolar concentration to F reversed F inhibition of PGDH mRNA levels. These findings suggest that F may be acting as an endogenous inhibitor of P(4) action in the regulation of PGDH at term.

New elements in human renin promoter involved in cell-specific expression.

1. The renin-angiotensin system plays a major role in blood pressure regulation and electrolyte homeostasis through the action of angiotensin (Ang) II. The first and rate-limiting step in the production of AngII is the conversion of angiotensinogen into AngI, which is catalysed by the aspartyl protease renin (EC 3.4.23.15). Circulating active renin is mainly synthesized, processed and secreted by the juxtaglomerular cells within the kidney. 2. To determine the renin 5'-flanking sequences involved in cell and tissue specificity, ex vivo and in vivo studies were performed. Several constructs of various lengths of renin promoter linked to the luciferase gene were first tested ex vivo by transfection in primary cultures of human chorionic cells. The constructs giving a high and specific expression in renin-producing cells were then tested in vivo in a transgenic mice model. 3. The reporter gene chosen to generate transgenic mice was LacZ and the screening was performed in embryos at the embryonic day (E) 15 stage, at which mouse renin is expressed in the developing vessels of the kidney. 4. Only constructs containing more than 5.7 kb of the human renin promoter lead to specific expression of beta-galactosidase in the kidney. 5. Our results demonstrate that the human renin distal promoter region allows a more restricted expression of LacZ in the renin-expressing cells in transgenic mice.

Dissection of silencer elements in first intron controlling the human renin gene.

A silencer within the renin first intron (intron A) was identified using Calu-6 cells, a pulmonary carcinoma cell line which produced renin. In the present study, a dissection of the first intron was performed to determine precisely the cis-regulatory elements involved in the silencer transcriptional effects. Intron A was completely sequenced to characterize potential binding sites for known transcription factors. Partial portions of intron A were subcloned upstream the 892 bp of the renin promoter and transfected in different models of renin-producing cells: primary culture of human chorionic cells, human Calu-6 cells and mouse As4.1 cells. There is significant DNA homology (67%) between the 3' and 5' ends of the human and rat renin first intron. Several transcription factor binding sites identified in human first intron, but not in rat intron, do not contribute to the reported silencer activity. Transfections of renin/ luciferase constructs containing partial portions of first intron inserted upstream of the 892 bp in both renin-producing cells do not allow the precise characterization of cis-elements involved in the silencer effect. The silencer located renin intron A is cell specific. The integrity of the human first intron seems necessary for its repressor activity on renin proximal promoter in renin-producing cells.