Involvement of transcription factor NR2F2 in human trophoblast differentiation

An atlas of small non-coding RNAs in human preimplantation development

Understanding the molecular circuitries that govern early embryogenesis is important, yet our knowledge of these in human preimplantation development remains limited. Small non-coding RNAs (sncRNAs) can regulate gene expression and thus impact blastocyst formation, however, the expression of specific biotypes and their dynamics during preimplantation development remains unknown. Here we identify the abundance of and kinetics of piRNA, rRNA, snoRNA, tRNA, and miRNA from embryonic day (E)3-7 and isolate specific miRNAs and snoRNAs of particular importance in blastocyst formation and pluripotency. These sncRNAs correspond to specific genomic hotspots: an enrichment of the chromosome 19 miRNA cluster (C19MC) in the trophectoderm (TE), and the chromosome 14 miRNA cluster (C14MC) and MEG8-related snoRNAs in the inner cell mass (ICM), which may serve as 'master regulators' of potency and lineage. Additionally, we observe a developmental transition with 21 isomiRs and in tRNA fragment (tRF) codon usage and identify two novel miRNAs. Our analysis provides a comprehensive measure of sncRNA biotypes and their corresponding dynamics throughout human preimplantation development, providing an extensive resource. Better understanding the sncRNA regulatory programmes in human embryogenesis will inform strategies to improve embryo development and outcomes of assisted reproductive technologies. We anticipate broad usage of our data as a resource for studies aimed at understanding embryogenesis, optimising stem cell-based models, assisted reproductive technology, and stem cell biology.

Cell-free DNA methylome analysis for early preeclampsia prediction

Preeclampsia (PE) is a leading cause for peripartal morbidity, especially if developing early in gestation. To enable prophylaxis in the prevention of PE, pregnancies at risk of PE must be identified early-in the first trimester. To identify at-risk pregnancies we profiled methylomes of plasma-derived, cell-free DNA from 498 pregnant women, of whom about one-third developed early-onset PE. We detected DNA methylation differences between control and PE pregnancies that enabled risk stratification at PE diagnosis but also presymptomatically, at around 12 weeks of gestation (range 9-14 weeks). The first-trimester risk prediction model was validated in an external cohort collected from two centers (area under the curve (AUC) = 0.75) and integrated with routinely available maternal risk factors (AUC = 0.85). The combined risk score correctly predicted 72% of patients with early-onset PE at 80% specificity. These preliminary results suggest that cell-free DNA methylation profiling is a promising tool for presymptomatic PE risk assessment, and has the potential to improve treatment and follow-up in the obstetric clinic.

Single-nuclei RNA sequencing (snRNA-seq) uncovers trophoblast cell types and lineages in the mature bovine placenta

Ruminants have a semi-invasive placenta, which possess highly vascularized placentomes formed by maternal endometrial caruncles and fetal placental cotyledons and required for fetal development to term. The synepitheliochorial placenta of cattle contains at least two trophoblast cell populations, including uninucleate (UNC) and binucleate (BNC) cells that are most abundant in the cotyledonary chorion of the placentomes. The interplacentomal placenta is more epitheliochorial in nature with the chorion developing specialized areolae over the openings of uterine glands. Of note, the cell types in the placenta and cellular and molecular mechanisms governing trophoblast differentiation and function are little understood in ruminants. To fill this knowledge gap, the cotyledonary and intercotyledonary areas of the mature day 195 bovine placenta were analyzed by single nuclei analysis. Single-nuclei RNA-seq analysis found substantial differences in cell type composition and transcriptional profiles between the two distinct regions of the placenta. Based on clustering and cell marker gene expression, five different trophoblast cell types were identified in the chorion, including proliferating and differentiating UNC and two different types of BNC in the cotyledon. Cell trajectory analyses provided a framework for understanding the differentiation of trophoblast UNC into BNC. The upstream transcription factor binding analysis of differentially expressed genes identified a candidate set of regulator factors and genes regulating trophoblast differentiation. This foundational information is useful to discover essential biological pathways underpinning the development and function of the bovine placenta.

Oxytocin modulates steroidogenesis-associated genes and estradiol levels in the placenta

Oxytocin (OXT) plays a significant role during pregnancy, especially toward the end of pregnancy. Some studies have reported that OXT is involved in the stimulation of steroidogenesis in several organs. However, the effects of OXT on placental steroidogenesis have not yet been established. In this study, we investigated the regulation of steroid hormones and steroidogenic enzymes by OXT-associated signaling in vitro and in vivo. OXT increased the gene expression of steroidogenic enzymes, which convert pregnenolone to progesterone and dehydroepiandrosterone (DHEA) in vitro. In OXT-administered pregnant rats, pregnenolone and DHEA levels were significantly enhanced in the plasma and the expression of the enzymes synthesizing DHEA, testosterone, and estradiol (E2) was increased in placental tissues. Furthermore, OXT was found to affect placental cell differentiation, which is closely related to steroid hormone synthesis. After treatment of the pregnant rats with atosiban, an antagonist of the OXT receptor, the concentration of E2 in the plasma and the expression of E2-synthesizing enzyme were reduced. This regulation may be due to OXT-mediated differentiation, because OXT increases the expression of corticotropin-releasing hormone, which is a biomarker of placental cell differentiation. Our findings suggest that OXT contributes to maintaining pregnancy by regulating the differentiation of placental cells and steroidogenesis during pregnancy.

Identifying novel regulators of placental development using time-series transcriptome data

The placenta serves as a connection between the mother and the fetus during pregnancy, providing the fetus with oxygen, nutrients, and growth hormones. However, the regulatory mechanisms and dynamic gene interaction networks underlying early placental development are understudied. Here, we generated RNA-sequencing data from mouse fetal placenta at embryonic days 7.5, 8.5, and 9.5 to identify genes with timepoint-specific expression, then inferred gene interaction networks to analyze highly connected network modules. We determined that timepoint-specific gene network modules were associated with distinct developmental processes, and with similar expression profiles to specific human placental cell populations. From each module, we identified hub genes and their direct neighboring genes, which were predicted to govern placental functions. We confirmed that four novel candidate regulators identified through our analyses regulate cell migration in the HTR-8/SVneo cell line. Overall, we predicted several novel regulators of placental development expressed in specific placental cell types using network analysis of bulk RNA-sequencing data. Our findings and analysis approaches will be valuable for future studies investigating the transcriptional landscape of early development.

How trophoblasts fuse: an in-depth look into placental syncytiotrophoblast formation

In humans, cell fusion is restricted to only a few cell types under normal conditions. In the placenta, cell fusion is a critical process for generating syncytiotrophoblast: the giant multinucleated trophoblast lineage containing billions of nuclei within an interconnected cytoplasm that forms the primary interface separating maternal blood from fetal tissue. The unique morphology of syncytiotrophoblast ensures that nutrients and gases can be efficiently transferred between maternal and fetal tissue while simultaneously restricting entry of potentially damaging substances and maternal immune cells through intercellular junctions. To maintain integrity of the syncytiotrophoblast layer, underlying cytotrophoblast progenitor cells terminate their capability for self-renewal, upregulate expression of genes needed for differentiation, and then fuse into the overlying syncytium. These processes are disrupted in a variety of obstetric complications, underscoring the importance of proper syncytiotrophoblast formation for pregnancy health. Herein, an overview of key mechanisms underlying human trophoblast fusion and syncytiotrophoblast development is discussed.

Downregulation of CDC42 inhibits the proliferation and stemness of human trophoblast stem cell via EZRIN/YAP inactivation

Placental dysplasia increases the risk of recurrent spontaneous abortion (RSA). However, the underlying mechanism regulating placental development remains unclear. In this study, we showed that the expression of CDC42 was decreased in the villous tissue of RSA samples compared to healthy controls. Further examination demonstrated that CDC42 deficiency led to the differentiation of human trophoblast stem cells (hTSCs) and inhibited their proliferation. Genetic manipulation of YAP and EZRIN in hTSCs revealed that CDC42 regulates the stemness and proliferation of hTSCs; this is dependent on EZRIN, which translocates YAP into the nucleus. Moreover, the expression pattern of EZRIN, YAP, and Ki67 was also abnormal in the villous tissue of RSA samples, consistent with in vitro experiments. In summary, these findings suggest that the CDC42/EZRIN/YAP pathway plays an important role in placental development.

Transcription factor networks in trophoblast development

The placenta sustains embryonic development and is critical for a successful pregnancy outcome. It provides the site of exchange between the mother and the embryo, has immunological functions and is a vital endocrine organ. To perform these diverse roles, the placenta comprises highly specialized trophoblast cell types, including syncytiotrophoblast and extravillous trophoblast. The coordinated actions of transcription factors (TFs) regulate their emergence during development, subsequent specialization, and identity. These TFs integrate diverse signaling cues, form TF networks, associate with chromatin remodeling and modifying factors, and collectively determine the cell type-specific characteristics. Here, we summarize the general properties of TFs, provide an overview of TFs involved in the development and function of the human trophoblast, and address similarities and differences to their murine orthologs. In addition, we discuss how the recent establishment of human in vitro models combined with -omics approaches propel our knowledge and transform the human trophoblast field.

Decidual NR2F2-Expressing CD4+ T Cells Promote TH2 Transcriptional Program During Early Pregnancy

A unique immunotolerant microenvironment with Th2 bias in the decidua provides an essential security for successful pregnancy. The disorganized maternal-fetal immune tolerance contributes to more than 50% of unexplained recurrent spontaneous abortion (RSA). How the Th2 bias is developed at the maternal-fetal interface remains undefined. NR2F2, a member of steroid/thyroid nuclear receptor superfamily, is endowed with diverse importance in cell-fate specification, organogenesis, angiogenesis, and metabolism. Here, we showed that NR2F2 was absolutely highly expressed in decidual CD4⁺T(dCD4⁺T) cells, but not in peripheral circulating CD4⁺T cells during early pregnancy. Decidual NR2F2-expressing CD4⁺T cells dominantly produced Th2 cytokines. In unexplained RSA patients, NR2F2 expression in dCD4⁺T cells was significantly decreased, accompanied with disordered phenotype of dCD4⁺T cells. Furthermore, overexpression of NR2F2 promoted the Th2 differentiation of naive CD4⁺T cells. Immunoprecipitation experiment confirmed the binding relationship between GATA-3 and NR2F2, which implied GATA-3 may be an important interactive element involved in the immunoregulatory process of NR2F2. This study is the first to reveal a previously unappreciated role for NR2F2-mediated dCD4⁺T cells in maternal-fetal immune tolerance and maintenance of normal pregnancy, in the hope of providing a potential biomarker for prediction and prevention of clinical unexplained RSA.

Severe acute respiratory syndrome coronavirus 2 may exploit human transcription factors involved in retinoic acid and interferon-mediated response: a hypothesis supported by an in silico analysis

The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing coronavirus disease 2019 (COVID-19), resulting in acute respiratory disease, is a worldwide emergency. Because recently it has been found that SARS-CoV is dependent on host transcription factors (TF) to express the viral genes, efforts are required to understand the molecular interplay between virus and host response. By bioinformatic analysis, we investigated human TF that can bind the SARS-CoV-2 sequence and can be involved in viral transcription. In particular, we analysed the key role of TF involved in interferon (IFN) response. We found that several TF could be induced by the IFN antiviral response, specifically some induced by IFN-stimulated gene factor 3 (ISGF3) and by unphosphorylated ISGF3, which were found to promote the transcription of several viral open reading frame. Moreover, we found 22 TF binding sites present only in the sequence of virus infecting humans but not bat coronavirus RaTG13. The 22 TF are involved in IFN, retinoic acid signalling and regulation of transcription by RNA polymerase II, thus facilitating its own replication cycle. This mechanism, by competition, may steal the human TF involved in these processes, explaining SARS-CoV-2's disruption of IFN-I signalling in host cells and the mechanism of the SARS retinoic acid depletion syndrome leading to the cytokine storm. We identified three TF binding sites present exclusively in the Brazilian SARS-CoV-2 P.1 variant that may explain the higher severity of the respiratory syndrome. These data shed light on SARS-CoV-2 dependence from the host transcription machinery associated with IFN response and strengthen our knowledge of the virus's transcription and replicative activity, thus paving the way for new targets for drug design and therapeutic approaches.

Placenta-Specific Genes, Their Regulation During Villous Trophoblast Differentiation and Dysregulation in Preterm Preeclampsia

The human placenta maintains pregnancy and supports the developing fetus by providing nutrition, gas-waste exchange, hormonal regulation, and an immunological barrier from the maternal immune system. The villous syncytiotrophoblast carries most of these functions and provides the interface between the maternal and fetal circulatory systems. The syncytiotrophoblast is generated by the biochemical and morphological differentiation of underlying cytotrophoblast progenitor cells. The dysfunction of the villous trophoblast development is implicated in placenta-mediated pregnancy complications. Herein, we describe gene modules and clusters involved in the dynamic differentiation of villous cytotrophoblasts into the syncytiotrophoblast. During this process, the immune defense functions are first established, followed by structural and metabolic changes, and then by peptide hormone synthesis. We describe key transcription regulatory molecules that regulate gene modules involved in placental functions. Based on transcriptomic evidence, we infer how villous trophoblast differentiation and functions are dysregulated in preterm preeclampsia, a life-threatening placenta-mediated obstetrical syndrome for the mother and fetus. In the conclusion, we uncover the blueprint for villous trophoblast development and its impairment in preterm preeclampsia, which may aid in the future development of non-invasive biomarkers for placental functions and early identification of women at risk for preterm preeclampsia as well as other placenta-mediated pregnancy complications.

Single-cell RNA sequencing reveals regulatory mechanism for trophoblast cell-fate divergence in human peri-implantation conceptuses

Multipotent trophoblasts undergo dynamic morphological movement and cellular differentiation after conceptus implantation to generate placenta. However, the mechanism controlling trophoblast development and differentiation during peri-implantation development in human remains elusive. In this study, we modeled human conceptus peri-implantation development from blastocyst to early postimplantation stages by using an in vitro coculture system and profiled the transcriptome of 476 individual trophoblast cells from these conceptuses. We revealed the genetic networks regulating peri-implantation trophoblast development. While determining when trophoblast differentiation happens, our bioinformatic analysis identified T-box transcription factor 3 (TBX3) as a key regulator for the differentiation of cytotrophoblast (CT) into syncytiotrophoblast (ST). The function of TBX3 in trophoblast differentiation is then validated by a loss-of-function experiment. In conclusion, our results provided a valuable resource to study the regulation of trophoblasts development and differentiation during human peri-implantation development.

Genome and epigenome analysis of monozygotic twins discordant for congenital heart disease

BACKGROUND

Congenital heart disease (CHD) is the leading non-infectious cause of death in infants. Monozygotic (MZ) twins share nearly all of their genetic variants before and after birth. Nevertheless, MZ twins are sometimes discordant for common complex diseases. The goal of this study is to identify genomic and epigenomic differences between a pair of twins discordant for a form of congenital heart disease, double outlet right ventricle (DORV).

RESULTS

A monoamniotic monozygotic (MZ) twin pair discordant for DORV were subjected to genome-wide sequencing and methylation analysis. We identified few genomic differences but 1566 differentially methylated regions (DMRs) between the MZ twins. Twenty percent (312/1566) of the DMRs are located within 2 kb upstream of transcription start sites (TSS), containing 121 binding sites of transcription factors. Particularly, ZIC3 and NR2F2 are found to have hypermethylated promoters in both the diseased twin and additional patients suffering from DORV.

CONCLUSIONS

The results showed a high correlation between hypermethylated promoters at ZIC3 and NR2F2 and down-regulated gene expression levels of these two genes in patients with DORV compared to normal controls, providing new insight into the potential mechanism of this rare form of CHD.

Alterted SLIT2/ROBO1 signalling is linked to impaired placentation of missed and threatened miscarriage in early pregnancy

AIMS

Two-thirds of early pregnancy failures present with reduced trophoblast invasion, and SLIT2/ROBO1 signalling is considered to play an important role in trophoblast function during pregnancy. We investigated SLIT2/ROBO1 signalling associated with missed and threatened miscarriage during early gestation.

METHODS AND RESULTS

Human placenta samples were collected from women with missed miscarriage (n = 25), threatened miscarriage (n = 22) and termination of pregnancy controls (n = 32). Corresponding decreases in beta human chorionic gonadotrophin (β-hCG) levels and shallow trophoblast invasion were observed in patients with missed and threatened miscarriage, immunohistological staining revealed abnormal Slit2 and Robo1, as well as E-cadherin and activating protein-2 alpha (AP-2α) expression in villi and extravillous trophoblasts, and the expression of these proteins were confirmed in villi and decidua of miscarriage material by Western blotting. Using HTR8/SVneo cells, blocking SLIT2/ROBO1 signalling promoted cell migration, proliferation and suppressed differentiation. Moreover, blocking SLIT2/ROBO1 signalling in HTR8/SVneo cells altered trophoblast differentiation-related and angiogenesis-related gene mRNA expression, which also occurred in the tissues of missed and threatened miscarriage.

CONCLUSIONS

SLIT2/ROBO1 signalling may regulate trophoblast differentiation and invasion causing restricting β-hCG production, shallow trophoblast invasion and inhibiting placental angiogenesis in missed and threatened miscarriage during the first trimester.

CRHR1 promoter hypomethylation: An epigenetic readout of panic disorder?

The corticotropin releasing hormone receptor 1 (CRHR1) is crucially involved in the hypothalamic-pituitary-adrenal axis and thus a major regulator of the stress response. CRHR1 gene variation is associated with several mental disorders including anxiety disorders. Studies in rodents have demonstrated epigenetic regulation of CRHR1 gene expression to moderate response to stressful environment. In the present study, we investigated CRHR1 promoter methylation for the first time regarding its role in panic disorder applying a case-control approach (N=131 patients, N=131 controls). In an independent sample of healthy volunteers (N=255), CRHR1 methylation was additionally analyzed for association with the Beck Anxiety Inventory (BAI) score as a dimensional panic-related intermediate phenotype. The functional relevance of altered CRHR1 promoter methylation was investigated by means of luciferase-based reporter gene assays. In panic disorder patients, a significantly decreased CRHR1 methylation was discerned (p<0.001). Accordingly, healthy controls with high BAI scores showed significantly decreased CRHR1 methylation. Functional analyses revealed an increased gene expression in presence of unmethylated as compared to methylated pCpGl_CRHR1 reporter gene vectors. The present study identified a potential role of CRHR1 hypomethylation - conferring increased CRHR1 expression - in panic disorder and a related dimensional intermediate phenotype. This up-regulation of CRHR1 gene expression driven by de-methylation might constitute a link between the stress response and panic disorder risk.

Convergent evolution of pregnancy-specific glycoproteins in human and horse

Pregnancy-specific glycoproteins (PSGs) are members of the carcinoembryonic antigen cell adhesion molecule (CEACAM) family that are secreted by trophoblast cells. PSGs may modulate immune, angiogenic and platelet responses during pregnancy. Until now, PSGs are only found in species that have a highly invasive (hemochorial) placentation including humans, mice and rats. Surprisingly, analyzing the CEACAM gene family of the horse, which has a non-invasive epitheliochorial placenta, with the exception of the transient endometrial cups, we identified equine CEACAM family members that seem to be related to PSGs of rodents and primates. We identified seven genes that encode secreted PSG-like CEACAMs Phylogenetic analyses indicate that they evolved independently from an equine CEACAM1-like ancestor rather than from a common PSG-like ancestor with rodents and primates. Significantly, expression of PSG-like genes (CEACAM44, CEACAM48, CEACAM49 and CEACAM55) was found in non-invasive as well as invasive trophoblast cells such as purified chorionic girdle cells and endometrial cup cells. Chorionic girdle cells are highly invasive trophoblast cells that invade the endometrium of the mare where they form endometrial cups and are in close contact with maternal immune cells. Therefore, the microenvironment of invasive equine trophoblast cells has striking similarities to the microenvironment of trophoblast cells in hemochorial placentas, suggesting that equine PSG-like CEACAMs and rodent and primate PSGs have undergone convergent evolution. This is supported by our finding that equine PSG-like CEACAM49 exhibits similar activity to certain rodent and human PSGs in a functional assay of platelet-fibrinogen binding. Our results have implications for understanding the evolution of PSGs and their functions in maternal-fetal interactions.

Transcriptomic signatures of villous cytotrophoblast and syncytiotrophoblast in term human placenta

During pregnancy, the placenta ensures multiple functions, which are directly involved in the initiation, fetal growth and outcome of gestation. The placental tissue involved in maternal-fetal exchanges and in synthesis of pregnancy hormones is the mononucleated villous cytotrophoblast (VCT) which aggregates and fuses to form and renew the syncytiotrophoblast (ST). Knowledge of the gene expression pattern specific to this endocrine and exchanges tissue of human placenta is of major importance to understand functions of this heterogeneous and complex tissue. Therefore, we undertook a global analysis of the gene expression profiles of primary cultured-VCT (n = 6) and in vitro-differentiated-ST (n = 5) in comparison with whole term placental tissue from which mononucleated VCT were isolated. A total of 880 differentially expressed genes (DEG) were observed between VCT/ST compared to whole placenta, and a total of 37 and 137 genes were significantly up and down-regulated, respectively, in VCT compared to ST. The 37 VCT-genes were involved in cellular processes (assembly, organization, and maintenance), whereas the 137 ST-genes were associated with lipid metabolism and cell morphology. In silico, all networks were linked to 3 transcriptional regulators (PPARγ, RARα and NR2F1) which are known to be essential for trophoblast differentiation. A subset of six DEG was validated by RT-qPCR and four by immunohistochemistry. To conclude, recognition of these pathways is fundamental to increase our understanding of the molecular basis of human trophoblast differentiation. The present study provides for the first time a gene expression signature of the VCT and ST compared to their originated term human placental tissue.

Scrutinising the regulators of syncytialization and their expression in pregnancy-related conditions

The placenta is important for the success of gestation and foetal development. In fact, this specialized pregnancy organ is essential for foetal nourishment, support, and protection. In the placenta, there are different cell populations, including four subtypes of trophoblasts. Cytotrophoblasts fuse and differentiate into the multinucleated syncytiotrophoblast (syncytialization). Syncytialization is a hallmark of placentation and is highly regulated by numerous molecules with distinct roles. Placentas from pregnancies complicated by preeclampsia, intrauterine growth restriction or trisomy 21 have been associated with a defective syncytialization and an altered expression of its modulators. This work proposes to review the molecules that promote or inhibit both fusion and biochemical differentiation of cytotrophoblasts. Moreover, it will also analyse the syncytialization modulators abnormally expressed in pathological placentas, highlighting the molecules that may contribute to the aetiology of these diseases.

Aberrant expression and regulation of NR2F2 and CTNNB1 in uterine fibroids

Uterine fibroids are the most common benign tumour afflicting women of reproductive age. Despite the large healthcare burden caused by fibroids, there is only limited understanding of the molecular mechanisms that drive fibroid pathophysiology. Although a large number of genes are differentially expressed in fibroids compared with myometrium, it is likely that most of these differences are a consequence of the fibroid presence and are not causal. The aim of this study was to investigate the expression and regulation of NR2F2 and CTNNB1 based on their potential causal role in uterine fibroid pathophysiology. We used real-time quantitative RT-PCR, western blotting and immunohistochemistry to describe the expression of NR2F2 and CTNNB1 in matched human uterine fibroid and myometrial tissues. Primary myometrial and fibroid smooth muscle cell cultures were treated with progesterone and/or retinoic acid (RA) and sonic hedgehog (SHH) conditioned media to investigate regulatory pathways for these proteins. We showed that NR2F2 and CTNNB1 are aberrantly expressed in fibroid tissue compared with matched myometrium, with strong blood vessel-specific localisation. Although the SHH pathway was shown to be active in myometrial and fibroid primary cultures, it did not regulateNR2F2orCTNNB1mRNA expression. However, progesterone and RA combined regulatedNR2F2mRNA, but notCTNNB1, in myometrial but not fibroid primary cultures. In conclusion, we demonstrate aberrant expression and regulation of NR2F2 and CTNNB1 in uterine fibroids compared with normal myometrium, consistent with the hypothesis that these factors may play a causal role uterine fibroid development.

MicroRNA-302 increases reprogramming efficiency via repression of NR2F2

MicroRNAs (miRNAs) have emerged as critical regulators of gene expression through translational inhibition and RNA decay and have been implicated in the regulation of cellular differentiation, proliferation, angiogenesis, and apoptosis. In this study, we analyzed global miRNA and mRNA microarrays to predict novel miRNA-mRNA interactions in human embryonic stem cells and induced pluripotent stem cells (iPSCs). In particular, we demonstrate a regulatory feedback loop between the miR-302 cluster and two transcription factors, NR2F2 and OCT4. Our data show high expression of miR-302 and OCT4 in pluripotent cells, while NR2F2 is expressed exclusively in differentiated cells. Target analysis predicts that NR2F2 is a direct target of miR-302, which we experimentally confirm by reporter luciferase assays and real-time polymerase chain reaction. We also demonstrate that NR2F2 directly inhibits the activity of the OCT4 promoter and thus diminishes the positive feedback loop between OCT4 and miR-302. Importantly, higher reprogramming efficiencies were obtained when we reprogrammed human adipose-derived stem cells into iPSCs using four factors (KLF4, C-MYC, OCT4, and SOX2) plus miR-302 (this reprogramming cocktail is hereafter referred to as "KMOS3") when compared to using four factors ("KMOS"). Furthermore, shRNA knockdown of NR2F2 mimics the over-expression of miR-302 by also enhancing reprogramming efficiency. Interestingly, we were unable to generate iPSCs from miR-302a/b/c/d alone, which is in contrast to previous publications that have reported that miR-302 by itself can reprogram human skin cancer cells and human hair follicle cells. Taken together, these findings demonstrate that miR-302 inhibits NR2F2 and promotes pluripotency through indirect positive regulation of OCT4. This feedback loop represents an important new mechanism for understanding and inducing pluripotency in somatic cells.

Direct regulation of caspase‑3 by the transcription factor AP‑2α is involved in aspirin‑induced apoptosis in MDA‑MB‑453 breast cancer cells

Aspirin has been reported to trigger apoptosis in various cancer cell lines. However, the detailed mechanisms involved remain elusive. The present study aimed to investigate whether aspirin plays a role in apoptosis of MDA-MB-453 cells. The effect of aspirin on the proliferation of human MDA-MB-453 cells breast cancer cells was evaluated using MTT assay, flow cytometry and western blotting. The present study reports that aspirin induces the apoptosis of MDA‑MB‑453 breast cancer cells which was attributed to the increased expression and activation of caspase‑3. Moreover, AP‑2α, a transcription factor highly expressed in MDA‑MB‑453 cells, was identified as a negative regulator of caspase‑3 transcription and AP‑2α was attenuated following aspirin treatment. Therefore, aspirin may increase the expression of caspase‑3 by inducing the degradation of AP‑2α, which increases activated caspase‑3 expression, thereby triggering apoptosis in MDA‑MB‑453 cells. Thus, aspirin may be used in breast cancer therapy.

Recent advances in understanding the endocrinology of human birth

The timing of human birth has a crucial impact upon the survival of the fetus. New knowledge on the regulation of human birth includes the role of endogenous retroviruses in the formation of the syncytiotrophoblast cells and consequently the secretion of corticotrophin releasing hormone, a hormone linked to gestational length determination. miRNAs have been identified that mediate progesterone withdrawal at labor by suppressing progesterone-induced transcription factors. Progress has also been made in understanding how the contractile machinery of the uterine myocytes is activated at labor and the role of small heat-shock proteins in this process. From this work, new therapeutic targets have been identified that may be used to regulate the onset of labor and improve neonatal mortality.

Gene targeting in primary human trophoblasts

Studies in primary human trophoblasts provide critical insights into placental function in normal and complicated pregnancies. Mechanistic studies in these cells require experimental tools to modulate gene expression. Lipid-based methods to transfect primary trophoblasts are fairly simple to use and allow for the efficient delivery of nucleic acids, but potential toxic effects limit these methods. Viral vectors are versatile transfection tools of native trophoblastic or foreign cDNAs, providing high transfection efficiency, low toxicity and stable DNA integration into the trophoblast genome. RNA interference (RNAi), using small interfering RNA (siRNA) or microRNA, constitutes a powerful approach to silence trophoblast genes. However, off-target effects, such as regulation of unintended complementary transcripts, inflammatory responses and saturation of the endogenous RNAi machinery, are significant concerns. Strategies to minimize off-target effects include using multiple individual siRNAs, elimination of pro-inflammatory sequences in the siRNA construct and chemical modification of a nucleotide in the guide strand or of the ribose moiety. Tools for efficient gene targeting in primary human trophoblasts are currently available, albeit not yet extensively validated. These methods are critical for exploring the function of human trophoblast genes and may provide a foundation for the future application of gene therapy that targets placental trophoblasts.

Establishment of human trophoblast progenitor cell lines from the chorion

Placental trophoblasts are key determinants of in utero development. Mouse trophoblast (TB) stem cells, which were first derived over a decade ago, are a powerful cell culture model for studying their self-renewal or differentiation. Our attempts to isolate an equivalent population from the trophectoderm of human blastocysts generated colonies that quickly differentiated in vitro. This finding suggested that the human placenta has another progenitor niche. Here, we show that the chorion is one such site. Initially, we immunolocalized pluripotency factors and TB fate determinants in the early gestation placenta, amnion, and chorion. Immunoreactive cells were numerous in the chorion. We isolated these cells and plated them in medium containing fibroblast growth factor which is required for human embryonic stem cell self-renewal, and an inhibitor of activin/nodal signaling. Colonies of polarized cells with a limited lifespan emerged. Trypsin dissociation yielded continuously self-replicating monolayers. Colonies and monolayers formed the two major human TB lineages-multinucleate syncytiotrophoblasts and invasive cytotrophoblasts (CTBs). Transcriptional profiling experiments revealed the factors associated with the self-renewal or differentiation of human chorionic TB progenitor cells (TBPCs). They included imprinted genes, NR2F1/2, HMGA2, and adhesion molecules that were required for TBPC differentiation. Together, the results of these experiments suggested that the chorion is one source of epithelial CTB progenitors. These findings explain why CTBs of fully formed chorionic villi have a modest mitotic index and identify the chorionic mesoderm as a niche for TBPCs that support placental growth.