Pregnancy-specific 1-glycoprotein Research Articles

Early Expression of Pregnancy-Specific Glycoprotein 22 (PSG22) by Trophoblast Cells Modulates Angiogenesis in Mice1

Mouse and human pregnancy-specific glycoproteins (PSG) are known to exert immunomodulatory functions during pregnancy by inducing maternal leukocytes to secrete anti-inflammatory cytokines that promote a tolerogenic decidual microenvironment. Many such anti-inflammatory mediators also function as proangiogenic factors, which, along with the reported association of murine PSG with the uterine vasculature, suggest that PSG may contribute to the vascular adaptations necessary for successful implantation and placental development. We observed that PSG22 is strongly expressed around the embryonic crypt on Gestation Day 5.5, indicating that trophoblast giant cells are the main source of PSG22 during the early stages of pregnancy. PSG22 treatment up-regulated the secretion of transforming growth factor beta 1 and vascular endothelial growth factor A (VEGFA) in murine macrophages, uterine dendritic cells, and natural killer cells. A possible role of PSGs in uteroplacental angiogenesis is further supported by the finding that incubation of endothelial cells with PSG22 resulted in the formation of tubes in the presence and absence of VEGFA. We determined that PSG22, like human PSG1 and murine PSG17 and PSG23, binds to the heparan sulfate chains in syndecans. Therefore, our findings indicate that despite the independent evolution and expansion of human and rodent PSG, members in both families have conserved functions that include their ability to induce anti-inflammatory cytokines and proangiogenic factors as well as to induce the formation of capillary structures by endothelial cells. In summary, our results indicate that PSG22, the most abundant PSG expressed during mouse early pregnancy, is likely a major contributor to the establishment of a successful pregnancy.

Pregnancy‐specific glycoprotein 1a activates dendritic cells to provide signals for Th17‐, Th2‐, and Treg‐cell polarization

Because of their plasticity and central role in orchestrating immunity and tolerance, DCs can respond to pregnancy-specific signals, thus promoting the appropriate immune response in order to support pregnancy. Here, we show that pregnancy-specific glycoprotein (PSG1a), the major variant of PSG released into the circulation during pregnancy, targets DCs to differentiate into a subset with a unique phenotype and function. This semi-mature phenotype is able to secrete IL-6 and TGF-β. PSG1a also affected the maturation of DCs, preventing the up-regulation of some costimulatory molecules, and inducing the secretion of TGF-β or IL-10 and the expression of programmed death ligand 1 (PD-L1) in response to TLR-9 or CD40 ligation. In addition, PSG1a-treated DCs promoted the enrichment of Th2-type cytokines, IL-17-producing cells, and Treg cells from CD4(+) T cells from DO11.10 Tg mice. Moreover, in vivo expression of PSG1a promoted the expansion of Ag-specific CD4(+) CD25(+) Foxp3(+) Treg cells and IL-17-, IL-4-, IL-5-, and IL-10-secreting cells able to protect against Listeria monocytogenes infection. Taken together, our data indicate that DCs can be targeted by PSG1a to generate the signals necessary to mount an appropriate, well-balanced, and effective immune response able to protect against invading pathogens while at the same time being compatible with a successful pregnancy.

Evolution of pregnancy-specific glycoproteins in mammals

Evolution of pregnancy-specific glycoproteins in mammals

Mutation and functional analysis of pregnancy-specific glycoprotein 1 (PSG1)

Mutation and functional analysis of pregnancy-specific glycoprotein 1 (PSG1)

A novel full-length isoform of murine pregnancy-specific glycoprotein 16 (psg16) is expressed in the brain but does not mediate murine coronavirus (MHV) entry

The mouse pregnancy-specific glycoprotein 16 (PSG16) has been reported to be an alternative receptor for mouse hepatitis virus (MHV), some strains of which cause encephalitis in mice lacking the canonical receptor CEACAM1a. The known isoforms of PSG16 are N-terminally truncated relative to other PSG family proteins and are expressed in neurons as well as in the placenta. We have cloned a novel full-length isoform of psg16 that is also expressed in the brain, placenta, and retina but, like the truncated form, lacks MHV receptor activity when expressed on 293T cells, suggesting that PSG16 does not mediate CEACAM1a-independent spread of MHV.

Mouse pregnancy-specific glycoproteins: tissue-specific expression and evidence of association with maternal vasculature

Mouse pregnancy-specific glycoproteins: tissue-specific expression and evidence of association with maternal vasculature

Krüppel-Like Factor 6 Expression Changes during Trophoblast Syncytialization and Transactivates ßhCG and PSG Placental Genes

BackgroundKrüppel-like factor-6 (KLF6) is a widely expressed member of the Sp1/KLF family of transcriptional regulators involved in differentiation, cell cycle control and proliferation in several cell systems. Even though the highest expression level of KLF6 has been detected in human and mice placenta, its function in trophoblast physiology is still unknown.Methodology/Principal FindingsHerein, we explored KLF6 expression and sub-cellular distribution in human trophoblast cells differentiating into the syncytial pathway, and its role in the regulation of genes associated with placental development and pregnancy maintenance. Confocal immunofluorescence microscopy demonstrated that KLF6 is expressed throughout human cytotrophoblast differentiation showing no evident modifications in its nuclear and cytoplasmic localization pattern. KLF6 transcript and protein peaked early during the syncytialization process as determined by qRT-PCR and western blot assays. Overexpression of KLF6 in trophoblast-derived JEG-3 cells showed a preferential nuclear signal correlating with enhanced expression of human β-chorionic gonadotropin (βhCG) and pregnancy-specific glycoprotein (PSG) genes. Moreover, KLF6 transactivated βhCG5, PSG5 and PSG3 gene promoters. Deletion of KLF6 Zn-finger DNA binding domain or mutation of the consensus KLF6 binding site abolished transactivation of the PSG5 promoter.Conclusions/SignificanceResults are consistent with KLF6 playing a role as transcriptional regulator of relevant genes for placental differentiation and physiology such as βhCG and PSG, in agreement with an early and transient increase of KLF6 expression during trophoblast syncytialization.

Characterization of receptors for murine pregnancy specific glycoproteins 17 and 23

In primates and rodents, trophoblast cells synthesize and secrete into the maternal circulation a family of proteins known as pregnancy specific glycoproteins (PSG). The current study was undertaken to characterize the receptor for two members of the murine PSG family, PSG17 and PSG23. Binding of recombinant PSG17 and PSG23 to CHO-K1 and L929 cells and their derived mutants was performed to determine whether these proteins bound to cell surface proteoglycans. We also examined binding of these proteins to cells transfected with syndecans and glypican-1 by flow cytometry. The interaction with glycosaminoglycans was confirmed in solid phase assays. Our results show that PSG17 binds to CD9 and to cell surface proteoglycans while PSG23 binds only to the latter. We found that the amino acids involved in CD9 binding reside in the region of highest divergence between the N1-domains of murine PSGs. For both proteins, the N-terminal domain (designated as N1) is sufficient for binding to cells and the ability to bind cell surface proteoglycans is affected by the cell line employed to generate the recombinant proteins. We conclude that while substantially different at the amino acid level, some murine PSGs share with human PSG1 the ability to bind to cell surface proteoglycans and that at least one PSG binds to more than one type of molecule on the cell surface.

Pregnancy-specific Glycoprotein 1 Induces Endothelial Tubulogenesis through Interaction with Cell Surface Proteoglycans

Pregnancy-specific β1 glycoproteins (PSGs) are the most abundant fetal proteins in the maternal bloodstream in late pregnancy. They are secreted by the syncytiotrophoblast and are detected around day 14 postfertilization. There are 11 human PSG genes, which encode a family of proteins exhibiting significant conservation at the amino acid level. We and others have proposed that PSGs have an immune modulatory function. In addition, we recently postulated that they are proangiogenic due to their ability to induce the secretion of VEGF-A and the formation of tubes by endothelial cells. The cellular receptor(s) for human PSGs remain unknown. Therefore, we conducted these studies to identify the receptor for PSG1, the highest expressed member of the family. We show that removal of cell surface glycosaminoglycans (GAGs) by enzymatic or chemical treatment of cells or competition with heparin completely inhibited binding of PSG1. In addition, PSG1 did not bind to cells lacking heparan or chondroitin sulfate on their surface, and binding was restored upon transfection with all four syndecans and glypican-1. Importantly, the presence of GAGs on the surface of endothelial cells was required for the ability of PSG1 to induce tube formation. This finding indicates that the PSG1-GAG interaction mediates at least some of the PSG1 proposed functions.

Problems and Perspectives in Diagnosis and Prevention of Ovarian Tumor Diseases

A set of embryonic proteins - potential markers for ovarian tumors is presented. More than ten new embryonic proteins have been tested, but no one strictly specific protein marker for diagnosis of ovarian tumors has been revealed. SOVA-1 is the most perspective marker for today. The special attention is given to peculiarities of evolution and mechanisms of early distribution of the tumor process. The role of pregnancy and “pregnancy specific glycoprotein”- PSG as a way of the ovary tumor disease prevention is discussed. An attempt to realize sources and logic of the disease is undertaken in the present work.

Receptor characterization of human pregnancy specific glycoprotein 1

Receptor characterization of human pregnancy specific glycoprotein 1

Involvement of Transcription Factor NR2F2 in Human Trophoblast Differentiation

BackgroundDuring the in vitro differentiation of human villous cytotrophoblast (CTB) cells to a syncytiotrophoblast (STB) phenotype, mRNA levels for the nuclear hormone receptor NR2F2 (ARP-1, COUP-TFII) increase rapidly, reaching a peak at day 1 of differentiation that is 8.8-fold greater than that in undifferentiated CTB cells. To examine whether NR2F2 is involved in the regulation of villous CTB cell differentiation, studies were performed to determine whether NR2F2 regulates the expression of TFAP2A (AP-2α), a transcription factor that is critical for the terminal differentiation of these cells to a STB phenotype.Methodology/Primary FindingsOverexpression of NR2F2 in primary cultures of human CTB cells and JEG-3 human choriocarcinoma cells induced dose-dependent increases in TFAP2A promoter activity. Conversely, siRNA mediated silencing of the NR2F2 gene in villous CTB undergoing spontaneous differentiation blocked the induction of the mRNAs for TFAP2A and several STB cell specific marker genes, including human placental lactogen (hPL), pregnancy specific glycoprotein 1 (PSG1) and corticotropin releasing hormone (CRH) by 51–59%. The induction of TFAP2A promoter activity by NR2F2 was potentiated by the nuclear hormone receptors retinoic acid receptor alpha (RARA) and retinoid X receptor alpha (RXRA).Conclusions/SignificanceTaken together, these results strongly suggest that NR2F2 is involved in villous CTB cell differentiation and that NR2F2 acts, at least in part, by directly activating TFAP2A gene expression and by potentiating the transactivation of TFAP2A by RARA and RXRA.

Coevolution of activating and inhibitory receptors within mammalian carcinoembryonic antigen families

BackgroundMost rapidly evolving gene families are involved in immune responses and reproduction, two biological functions which have been assigned to the carcinoembryonic antigen (CEA) gene family. To gain insights into evolutionary forces shaping the CEA gene family we have analysed this gene family in 27 mammalian species including monotreme and marsupial lineages.ResultsPhylogenetic analysis provided convincing evidence that the primordial CEA gene family in mammals consisted of five genes, including the immune inhibitory receptor-encoding CEACAM1 (CEA-related cell adhesion molecule) ancestor. Our analysis of the substitution rates within the nucleotide sequence which codes for the ligand binding domain of CEACAM1 indicates that the selection for diversification is, perhaps, a consequence of the exploitation of CEACAM1 by a variety of viral and bacterial pathogens as their cellular receptor. Depending on the extent of the amplification of an ancestral CEACAM1, the number of CEACAM1-related genes varies considerably between mammalian species from less than five in lagomorphs to more than 100 in bats. In most analysed species, ITAM (immunoreceptor tyrosine-based activation motifs) or ITAM-like motif-containing proteins exist which contain Ig-V-like, ligand binding domains closely related to that of CEACAM1. Human CEACAM3 is one such protein which can function as a CEACAM1 decoy receptor in granulocytes by mediating the uptake and destruction of specific bacterial pathogens via its ITAM-like motif. The close relationship between CEACAM1 and its ITAM-encoding relatives appears to be maintained by gene conversion and reciprocal recombination. Surprisingly, secreted CEACAMs resembling immunomodulatory CEACAM1-related trophoblast-specific pregnancy-specific glycoproteins (PSGs) found in humans and rodents evolved only in a limited set of mammals. The appearance of PSG-like genes correlates with invasive trophoblast growth in these species.ConclusionsThese phylogenetic studies provide evidence that pathogen/host coevolution and a possible participation in fetal-maternal conflict processes led to a highly species-specific diversity of mammalian CEA gene families.

Expression and Transcriptional Regulation of Individual Pregnancy-specific Glycoprotein Genes in Differentiating Trophoblast Cells

Human pregnancy-specific glycoproteins (PSGs), encoded by eleven highly conserved genes, are the major placental polypeptides. Low PSG levels in maternal circulation have been associated with complicated pregnancies. However, expression of each PSG gene and their regulation during cytotrophoblast cell differentiation remain poorly explored. Herein, we analyze the expression of five PSG genes and demonstrate that they are almost undetectable in undifferentiated trophoblast, but are all transcribed in differentiated cells. Among them, PSG1, PSG3 and PSG5 genes achieve high mRNA levels while PSG7 and PSG9 are poorly expressed. In addition, total PSG proteins and transcripts markedly increase during trophoblast differentiation, preceding morphological syncytialization and βhCG expression. The 5′ regulatory region contributes to the transcriptional control of PSG gene induction in trophoblast cells undergoing differentiation. This responsive region in PSG3 maps within a 130 bp promoter sequence, which overlaps the transcription start site and requires a functional Retinoic Acid Responsive Element (RARE) and a GA-binding protein (GABP) consensus site for basal and differentiation-dependent promoter activity, respectively. Present findings provide novel data for understanding the control of PSG gene expression and demonstrate that their proteins and transcripts represent early markers of trophoblast differentiation.

Radical gain and loss of CEACAM/PSG family genes in vertebrates

In placental mammals, a family of recently evolved tumor suppressor genes, carcinoembryonic antigen cell adhesion molecules (CEACAMs), and related pregnancy‐specific glycoproteins (PSGs) are critical to the regulation of tumorigenesis, fetal‐maternal interaction, and pathogen transmission. Despite having important roles in many basic physiological processes, these genes were believed to be "eutherian‐specific"; how they evolved remains a mystery. Based on syntenic mapping analyses, we reveal that, surprisingly, a large number of diverging CEACAM orthologs is present from teleosts to marsupial mammals. In addition, based on the deduced ancestral genotypes, we infer that the CEACAM gene family evolved from a couple of ancestral genes in the common ancestor of teleosts and tetrapods. Taken together, contrary to the conventional view that CEACAMs are placental mammal‐specific, our study reveals that CEACAM family genes represent an independent branch of the immunoglobulin superfamily that evolved early in vertebrates. Furthermore, while the observed accelerated gene gain of CEACAMs in therian mammals could be partly attributed to the presence of repetitive sequences and a lower genetic constraint associated with cell surface receptors, we propose an alternative evolution model to account for the radical changes in the CEACAM gene inventory.The abstract was partly supported by the Taiwan National Health Research Institute grant HMRPG380011 and the NIDDK grant DK70652.

Coordinate expression of the human pregnancy-specific glycoprotein gene family during induced and replicative senescence

Pregnancy-specific glycoproteins (PSGs) comprise a family of highly similar polypeptides encoded by 11 transcriptionally active genes that compactly cluster on band 19q13.2. All members of the PSG family were found to be markedly up-regulated by addition of 5-bromodeoxyuridine in HeLa cells. Similarly, all of the members were markedly up-regulated during replicative senescence in normal human fibroblasts. Promoter analysis of the PSG1, 4, and 11 genes in HeLa cells did not reveal a cis-regulatory element responsive to 5-bromodeoxyuridine in their 5'-flanking sequences. These results suggest that the PSG genes are regulated at a level of higher order chromatin structure besides by a signal of pregnancy.

Murine Pregnancy-Specific Glycoprotein 23 Induces the Proangiogenic Factors Transforming-Growth Factor Beta 1 and Vascular Endothelial Growth Factor A in Cell Types Involved in Vascular Remodeling in Pregnancy1

Haemochorial placentation is a unique physiological process in which the fetal trophoblast cells remodel the maternal decidual spiral arteries to establish the fetoplacental blood supply. Pregnancy-specific glycoproteins (PSGs) are members of the carcinoembryonic antigen family. PSGs are produced by the placenta of rodents and primates and are secreted into the bloodstream. PSG23 is one of 17 members of the murine PSG family (designated PSG16 to PSG32). Previous studies determined that PSGs have immunoregulatory functions due to their ability to modulate macrophage cytokine secretion. Here we show that recombinant PSG23 induces transforming growth factor (TGF) beta1, TGFB1, and vascular endothelial growth factor A (VEGFA) in primary murine macrophages and the macrophage cell line RAW 264.7 cells. In addition, we identified new cell types that responded to PSG23 treatment. Dendritic cells, endothelial cells, and trophoblasts, which are involved in maternal vasculature remodeling during pregnancy, secreted TGFB1 and VEGFA in response to PSG23. PSG23 showed cross-reactivity with human cells, including human monocytes and the trophoblast cell line, HTR-8/SVneo cells. We analyzed the binding of PSG23 to the tetraspanin CD9, the receptor for PSG17, and found that CD9 is not essential for PSG23 binding and activity in macrophages. Overall these studies show that PSGs can modulate the secretion of important proangiogenic factors, TGFB1 and VEGFA, by different cell types involved in the development of the placenta.

Radical Divergence of CEACAM Family Genes in Mammals.

In mammals, a plethora of recently evolved CEACAM family proteins have been found to play tumor suppressor functions or serve as tumor markers in various tumors. The CEACAM gene family, comprising the CEA cell adhesion molecules (CEACAM) and the pregnancy-specific glycoproteins (PSG), is situated at the crossroads of a network of signaling pathways that are important for a variety of cellular activities. CEACAM proteins have been associated with maternal-fetal interaction, insulin signaling turnover, differentiation of mammary gland, angiogenesis, viral and bacterial pathogen transmission, as well as the modulation of innate and adaptive immune responses. On the other hand, PSGs were characterized as major proteins from human syncytiotrophoblasts starting as early as the time of implantation, and shown to be necessary for normal pregnancy. Despite their important functions, how CEACAM family genes and their associated functions evolved remains unclear. Thus far, CEACAMs were described only in placental mammals, and were considered to be placental mammal-specific. Based on the understanding that tumor suppressor genes likely have an ancient origin, we explored the evolutionary path of CEACAM family genes based on syntenic mapping of the CEACAM locus in vertebrate genomes. Here, we show that orthologous CEACAMs are present in both monotreme and marsupial mammals. Whereas the genome of opossum (Monodelphis domestica) encodes two clusters of diverging CEACAM orthologs and paralogs, the platypus (Ornithorhynchus anatinus) likely encodes only three CEACAM homologs. In addition, phylogenetic studies suggested that the diverging human CEACAM family genes likely evolved from three or four CEACAM ancestors in the common ancestor of monotremes, marsupials and placentals. In contrast, the human PSG subfamily genes likely represent primate-specific CEACAM gene duplicates. Hence, our study demonstrated that CEACAM family genes evolved early in mammals and a Darwinian selection of CEACAM-mediated intercellular communications in vertebrates.

Placenta-Derived, Cellular Messenger RNA Expression in the Maternal Blood of Preeclamptic Women

To perform gene expression profiling and real-time quantitative reverse-transcription polymerase chain reaction (PCR) analysis to identify biomarkers of preeclampsia in cellular messenger RNA (mRNA) from maternal blood. We performed a microarray analysis with five maternal blood samples from women with preeclampsia and five matched control subjects. Up-regulated gene expression was further analyzed through reverse-transcription PCR analysis with 28 consecutive blood samples from women affected with preeclampsia and 29 controls. Both pregnancy-specific beta1 glycoprotein and trophoblast glycoprotein were selected based on microarray analysis. Reverse-transcription PCR analysis detected significantly increased mRNA concentrations among women in the preeclampsia group. When stratified according to mild or severe preeclampsia, 19.2-fold and 41.8-fold increases in pregnancy-specific beta1 glycoprotein and 8.3-fold and 10.6-fold increases in trophoblast glycoprotein were observed, respectively. Among women with hemolysis, elevated liver enzymes, and low platelet count syndrome, 51.6-fold and 13.1-fold increases in pregnancy-specific beta1 glycoprotein and trophoblast glycoprotein were observed, respectively. In the preeclampsia group, pregnancy-specific beta1 glycoprotein correlated with severity of proteinuria (P<.001) and systolic blood pressure (P=.01). The mRNA expression of pregnancy-specific beta1 glycoprotein and trophoblast glycoprotein is up-regulated in cells circulating within blood from women with preeclampsia, and pregnancy-specific beta1 glycoprotein expression is positively correlated with the clinical severity of preeclampsia. II.

RXRα Regulates the Pregnancy-Specific Glycoprotein 5 Gene Transcription Through a Functional Retinoic Acid Responsive Element

Human pregnancy-specific glycoproteins (PSG) are major placental polypeptides encoded by eleven highly conserved genes expressed by the syncytiotrophoblast. The minimal promoter region of all PSG genes contains a putative Retinoic Acid Responsive Element (RARE) though the ability of retinoids to regulate PSG gene expression has not been established. Retinoid signaling pathway plays a key role for overall placenta biology and is essential for trophoblast differentiation. In this work, we investigated the participation of the RARE motif in the regulation of PSG5 gene transcription by retinoic acid and its receptors. The minimal promoter region of PSG5 gene was activated by RXRα but not by RARα, in a ligand-dependent manner. The RARE sequence of PSG5 gene promoter was recognized by endogenous RXRα present in placental nuclear extracts as well as by RXRα either over expressed in cultured non-placental cells or in vitro translated. Mutations at specific nucleotides within the RARE motif abrogated both RXRα DNA binding and transcriptional activation of PSG5 promoter mediated by RXRα. Moreover, endogenous PSG expression was significantly induced in trophoblast-derived Jeg-3 cells upon 9-cis retinoic acid treatment. Interestingly, the induction level was higher following methotrexate-induced differentiation of Jeg-3 cells to syncytiotrophoblast-like structures. Altogether, these data provide the first evidences demonstrating that transcriptional activity of PSG5 gene is responsive to an external signal involving the retinoids-RXRα axis through a conserved RARE motif shared by all PSG gene family members.