Involvement of Epac1/Rap1/CaMKI/HDAC5 signaling cascade in the regulation of placental cell fusion

The Research Progress of DNA Methylation in the Development and Function of the Porcine Placenta

The pig is the most widely consumed domestic animal in China, providing over half of the meat supply in food markets. For livestock, a key economic trait is the reproductive performance, which is significantly influenced by placental development. The placenta, a temporary fetal organ, is crucial for establishing maternal-fetal communication and supporting fetal growth throughout pregnancy. DNA methylation is an epigenetic modification that can regulate the gene expression by recruiting proteins involved in gene silencing or preventing transcription factor binding. To enhance our understanding of the molecular mechanisms underlying DNA methylation in porcine placental development, this review summarizes the structure and function of the porcine placenta and the role of DNA methylation in placental development.

NOTCH3 signalling controls human trophoblast stem cell expansion and differentiation

Failures in growth and differentiation of the early human placenta are associated with severe pregnancy disorders such as pre-eclampsia and fetal growth restriction. However, regulatory mechanisms controlling development of placental epithelial cells, the trophoblasts, remain poorly elucidated. Using trophoblast stem cells (TSCs), trophoblast organoids (TB-ORGs) and primary cytotrophoblasts (CTBs) of early pregnancy, we herein show that autocrine NOTCH3 signalling controls human placental expansion and differentiation. The NOTCH3 receptor was specifically expressed in proliferative CTB progenitors and its active form, the nuclear NOTCH3 intracellular domain (NOTCH3-ICD), interacted with the transcriptional co-activator mastermind-like 1 (MAML1). Doxycycline-inducible expression of dominant-negative MAML1 in TSC lines provoked cell fusion and upregulation of genes specific for multinucleated syncytiotrophoblasts, which are the differentiated hormone-producing cells of the placenta. However, progenitor expansion and markers of trophoblast stemness and proliferation were suppressed. Accordingly, inhibition of NOTCH3 signalling diminished growth of TB-ORGs, whereas overexpression of NOTCH3-ICD in primary CTBs and TSCs showed opposite effects. In conclusion, the data suggest that canonical NOTCH3 signalling plays a key role in human placental development by promoting self-renewal of CTB progenitors.

Integrated Analysis of DNA Methylation and Gene Expression in Porcine Placental Development

Proper placental development is crucial for the conceptus to grow and survive, because the placenta is responsible for transporting nutrients and oxygen from the pregnant female to the developing fetus. However, the processes of placental morphogenesis and fold formation remain to be fully elucidated. In this study, we used whole-genome bisulfite sequencing and RNA sequencing to produce a global map of DNA methylation and gene expression changes in placentas from Tibetan pig fetuses 21, 28, and 35 days post-coitus. Substantial changes in morphology and histological structures at the uterine-placental interface were revealed via hematoxylin-eosin staining. Transcriptome analysis identified 3959 differentially expressed genes (DEGs) and revealed the key transcriptional properties in three stages. The DNA methylation level in the gene promoter was negatively correlated with gene expression. We identified a set of differentially methylated regions associated with placental developmental genes and transcription factors. The decrease in DNA methylation level in the promoter was associated with the transcriptional activation of 699 DEGs that were functionally enriched in cell adhesion and migration, extracellular matrix remodeling, and angiogenesis. Our analysis provides a valuable resource for understanding the mechanisms of DNA methylation in placental development. The methylation status of different genomic regions plays a key role in establishing transcriptional patterns from placental morphogenesis to fold formation.

Whole genome bisulfite sequencing of sperm reveals differentially methylated regions in male partners of idiopathic recurrent pregnancy loss cases

OBJECTIVE

To study the genome wide alterations in sperm DNA methylation in male partners of idiopathic recurrent pregnancy loss (iRPL) cases and note regions as potential diagnostic markers.

DESIGN

Case-control study and methylome analysis of human sperm.

SETTING

Obstetrics and Gynaecology clinics.

PATIENT(S)

Control group consists of apparently healthy fertile men having fathered a child within the last 2 years (n = 39); and case group consists of male partners of iRPL cases having ≥2 consecutive 1st trimester pregnancy losses (n = 47).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Sperm DNA samples of controls and cases were selected for whole genome bisulfite sequencing analysis based on the previously set thresholds of global methylation levels and methylation levels of imprinted genes (KvDMR and ZAC). Whole genome bisulfite sequencing of selected sperm genomic DNA was performed to identify differentially methylated CpG sites of iRPL cases compared with fertile controls. Pathway analysis of all the differentially methylated genes was done by Database for Annotation, Visualization, and Integrated Discovery annotation tool and Kyoto Encyclopedia of Genes and Genomes tool. Differentially methylated CpGs within genes relevant to embryo and placenta development were selected to further validate their methylation levels in study population by pyrosequencing.

RESULT(S)

A total of 9497 differentially methylated CpGs with highest enrichment in intronic regions were obtained. In addition, 5352 differentially methylated regions and 2087 differentially methylated genes were noted. Signaling pathways involved in development were enriched on pathway analysis. Select CpGs within genes PPARG, KCNQ1, SETD2, and MAP3K4 showed distinct hypomethylated subpopulations within iRPL study population.

CONCLUSION(S)

Our study highlights the altered methylation landscape of iRPL sperm, and their possible implications in pathways of embryo and placental development. The CpG sites that are hypomethylated specifically in sperm of iRPL subpopulation can be further assessed as predictive biomarkers.

HDAC5 inactivates CYR61-regulated CD31/mTOR axis to prevent the occurrence of preeclampsia

Our study was to pinpoint the significance of histone deacetylase 5 (HDAC5) affecting the pathogenesis of preeclampsia (PE) via CD31/mammalian target of rapamycin (mTOR) axis by regulating cysteine-rich angiogenic inducer 61 (CYR61). Expression of HDAC5, CYR61, and CD31/mTOR in placental tissues of patients with PE and trophoblast cells HTR-8/SVneo cells was determined first followed by their interaction analysis. Following different transfection, the significance of HDAC5 in cell functions was assayed in relation to CYR61 and CD31/mTOR. An in vivo PE mouse model was constructed for further validation. The clinical tissue and in vitro cell experimentations discovered that HDAC5 was downregulated in placental tissues of PE patients and trophoblast cells, while CYR61, CD31, mTOR, and p-mTOR displayed upregulation. After overexpression of HDAC5, trophoblast cell functions were enhanced. HDAC5 reduced the acetylation enrichment of H3K27 to inhibit the expression of CYR61. Furthermore, CYR61 promoted the activation of CD31/mTOR axis, thereby inhibiting HTR-8/SVneo cell functions. The in vivo rat model confirmed the above alterations. Taken together, HDAC5 contributes to downregulation of CYR61 through histone deacetylation, inactivating CD31/mTOR axis, which prevents the occurrence and development of PE.

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.

Functional antagonism between ΔNp63α and GCM1 regulates human trophoblast stemness and differentiation

The combination of EGF, CHIR99021, A83-01, SB431542, VPA, and Y27632 (EGF/CASVY) facilitates the derivation of trophoblast stem (TS) cells from human blastocysts and first-trimester, but not term, cytotrophoblasts. The mechanism underlying this chemical induction of TS cells remains elusive. Here we demonstrate that the induction efficiency of cytotrophoblast is determined by functional antagonism of the placental transcription factor GCM1 and the stemness regulator ΔNp63α. ΔNp63α reduces GCM1 transcriptional activity, whereas GCM1 inhibits ΔNp63α oligomerization and autoregulation. EGF/CASVY cocktail activates ΔNp63α, thereby partially inhibiting GCM1 activity and reverting term cytotrophoblasts into stem cells. By applying hypoxia condition, we can further reduce GCM1 activity and successfully induce term cytotrophoblasts into TS cells. Consequently, we identify mitochondrial creatine kinase 1 (CKMT1) as a key GCM1 target crucial for syncytiotrophoblast differentiation and reveal decreased CKMT1 expression in preeclampsia. Our study delineates the molecular underpinnings of trophoblast stemness and differentiation and an efficient method to establish TS cells from term placentas.

Trophoblast stem cells can be derived from human blastocysts and first-trimester, but not term, cytotrophoblasts. Here the authors show that induction efficiency of cytotrophoblast is determined by antagonism between GCM1 and ΔNp63α and manipulating this antagonism facilitates derivation of TS cells from term placenta.

Screening Candidate Genes Regulating Placental Development from Trophoblast Transcriptome at Early Pregnancy in Dazu Black Goats (Capra hircus)

Simple Summary

The trophoblast is an original placental tissue whose normal proliferation, differentiation, migration, adhesion, and angiopoiesis are essential for placenta formation and fetal survival during early pregnancy. However, the key genes and molecular mechanisms involved in placenta development in goats are unknown. Herein, the morphology and histological structures of trophoblast tissues from day 20 to 30 of pregnancy were determined. RNA-sequencing was used to screen potential functional genes in common highly expressed and differentially expressed genes. RAP1 signaling pathway was used as the contact center and coordinated with other pathways to regulate placenta development. This study could provide insights into the molecular mechanisms underlying ruminant placentation.

Abstract

This study explored the trophoblast transcriptome to understand potential functional genes involved in early placental development in goats and their enriched signaling pathways. Trophoblast samples were collected from nine Dazu Black goats on days 20, 25, and 30 of pregnancy (D20, D25, and D30). As the pregnancy progressed, the morphology and histological structures showed significant growth, adhesion, and angiogenesis. A total of 23,253 commonly expressed genes (CEGs) and 4439 differently expressed genes (DEGs) were detected by RNA sequencing. The common highly expressed genes (ChEGs) (the top 100 CEGs) with the highest FPKM percentage (29.9%) of all CEGs were annotated to the ribosome pathway and maintain pregnancy. DEGs were abundant in D30 vs. D20 (3715 DEGs). Besides, the DEGs were associated with the inhibition of oxidative phosphorylation and activation of PI3K-Akt, focal adhesion, ECM–receptor interaction, Rap1, and CAM signaling pathways. The RAP1 may be a central pathway since it coordinates with others to regulate the cell proliferation, invasion, migration, and fusion of trophoblasts. qRT-PCR and Western blot analysis confirmed the transcriptional expression in IGF1, VEGFC, RAPGEF3, PIK3CA, AKT3, ITGB3, ITGA11, SPP1, NOS1, and ATP6V0B genes and protein levels in VEGF, RAPGEF3, and Akt. This is the first study of transcriptome profiling in goat placenta and provides diverse genetic resources for further research on placenta development.

Age and Sex-Related Changes in Human First-Trimester Placenta Transcriptome and Insights into Adaptative Responses to Increased Oxygen

Physiological oxygen tension rises dramatically in the placenta between 8 and 14 weeks of gestation. Abnormalities in this period can lead to gestational diseases, whose underlying mechanisms remain unclear. We explored the changes at mRNA level by comparing the transcriptomes of human placentas at 8–10 gestational weeks and 12–14 gestational weeks. A total of 20 samples were collected and divided equally into four groups based on sex and age. Cytotrophoblasts were isolated and sequenced using RNAseq. Key genes were identified using two different methods: DESeq2 and weighted gene co-expression network analysis (WGCNA). We also constructed a local database of known targets of hypoxia-inducible factor (HIF) subunits, alpha and beta, to investigate expression patterns likely linked with changes in oxygen. Patterns of gene enrichment in and among the four groups were analyzed based on annotations of gene ontology (GO) and KEGG pathways. We characterized the similarities and differences between the enrichment patterns revealed by the two methods and the two conditions (age and sex), as well as those associated with HIF targets. Our results provide a broad perspective of the processes that are active in cytotrophoblasts during the rise in physiological oxygen, which should benefit efforts to discover possible drug-targeted genes or pathways in the human placenta.

Lysine acetylation of cytoskeletal proteins: Emergence of an actin code

Reversible lysine acetylation of nuclear proteins such as histones is a long-established important regulatory mechanism for chromatin remodeling and transcription. In the cytoplasm, acetylation of a number of cytoskeletal proteins, including tubulin, cortactin, and the formin mDia2, regulates both cytoskeletal assembly and stability. More recently, acetylation of actin itself was revealed to regulate cytoplasmic actin polymerization through the formin INF2, with downstream effects on ER-to-mitochondrial calcium transfer, mitochondrial fission, and vesicle transport. This finding raises the possibility that actin acetylation, along with other post-translational modifications to actin, might constitute an "actin code," similar to the "histone code" or "tubulin code," controlling functional shifts to these central cellular proteins. Given the multiple roles of actin in nuclear functions, its modifications might also have important roles in gene expression.

Hypoxia-inducible factor 2 alpha impairs human cytotrophoblast syncytialization: New insights into placental dysfunction and fetal growth restriction

Insufficient remodeling of uterine arteries causes pregnancy-related diseases, including fetal growth restriction and preeclampsia. In these situations, reduced maternal blood flow in the placenta is thought to be responsible for the persistence of a low oxygen environment throughout pregnancy. We hypothesized that chronic activation of transcription factors hypoxia-inducible factors (HIFs) actively participates in placental underdevelopment, which impairs fetal growth. The computer-assisted analysis in pathological placentas revealed an increased number of HIF-2α-positive nuclei in the syncytium compared to normal human placentas, while HIF-1α stabilization was unchanged. Specific involvement of HIF-2α was confirmed in primary human cytotrophoblasts rendered deficient for HIF1A or HIF2A. Silencing HIF2A increased the expression of main syncytialization markers as well as differentiation and syncytium formation. It also improved placental growth factor bioavailability. None of these changes was seen when silencing HIF1A. Conversely, the experimental induction of HIF-2α expression repressed forskolin-induced differentiation in BeWo choriocarcinoma cells. Our mechanistic insights evidence that transcription factor HIF-2α impairs placental function, thus suggesting its participation in fetal growth restriction and preeclampsia when placentas become chronically hypoxic. Furthermore, it suggests the possibility to develop novel molecular targeting therapies for placental dysfunction.

Mining of combined human placental gene expression data across pregnancy, applied to PPAR signaling pathway

INTRODUCTION

To date, we have only an incomplete understanding of how gene expression in the human placenta changes at the genome-wide scale from very early in gestation to term. Our aim was to investigate the dynamic changes in gene expression throughout placentation.

METHODS

In our study, gene expression profiles were collected of human placentas from 4 to 40 gestational weeks of age. Simple linear regression and weighted correlation network analysis were applied to identify genes of interest. Analyses of gene enrichment, including gene ontology and pathways from the Kyoto Encyclopedia of Genes and Genomes, were performed using clusterProfiler. Finally, dynamic changes in the expression of individual genes were represented using line graphs of scaled and adjusted gene expression.

RESULTS

Our results highlighted a total of 5173 genes that are involved in different periods of placentation. Downstream annotation of these genes revealed the biological processes and pathways involved, from which we chose to further investigate the PPAR signaling pathway. We were able to detect changes over time in many genes involved in lipid storage/metabolism, including members of the FABP family and LPL. These patterns were corroborated by lipid staining of placental sections, which revealed a significant decrease in lipid droplet content in placentas from early in the first trimester to term.

CONCLUSION

Our study provides detailed information on the dynamics of biological processes and pathways across human placentation. These findings give us new clues for deciphering the normal functions of placentation and the ways in which the mis-regulation of these pathways may be linked to pregnancy-related diseases. As an example, our results show that the PPAR signaling pathway mediates a constant decrease in placental lipid content over the course of pregnancy.

Transcriptomic profiling of trophoblast fusion using BeWo and JEG-3 cell lines

In human placenta, alteration in trophoblast differentiation has a major impact on placental maintenance and integrity. However, little is known about the mechanisms that control cytotrophoblast fusion. The BeWo cell line is used to study placental function, since it forms syncytium and secretes hormones after treatment with cAMP or forskolin. In contrast, the JEG-3 cell line fails to undergo substantial fusion. Therefore, BeWo and JEG-3 cells were used to identify a set of genes responsible for trophoblast fusion. Cells were treated with forskolin for 48 h to induce fusion. RNA was extracted, hybridised to Affymetrix HuGene ST1.0 arrays and analysed using system biology. Trophoblast differentiation was evaluated by real-time PCR and immunocytochemistry analysis. Moreover, some of the identified genes were validated by real-time PCR and their functional capacity was demonstrated by western blot using phospho-specific antibodies and CRISPR/cas9 knockdown experiments. Our results identified a list of 32 altered genes in fused BeWo cells compared to JEG-3 cells after forskolin treatment. Among these genes, four were validated by RT-PCR, including salt-inducible kinase 1 (SIK1) gene which is specifically upregulated in BeWo cells upon fusion and activated after 2 min with forskolin. Moreover, silencing of SIK1 completely abolished the fusion. Finally, SIK1 was shown to be at the center of many biological and functional processes, suggesting that it might play a role in trophoblast differentiation. In conclusion, this study identified new target genes implicated in trophoblast fusion. More studies are required to investigate the role of these genes in some placental pathology.

Decreased H3K9 acetylation level of LXRα mediated dexamethasone-induced placental cholesterol transport dysfunction

Due to the insufficient fetal cholesterol synthesis, maternal cholesterol transport through the placenta becomes an important source of fetal cholesterol pool, which is essential for fetal growth and development. This study aimed to investigate the effects of dexamethasone on fetal cholesterol levels, and explore its placental mechanism. Pregnant Wistar rats were injected subcutaneously with dexamethasone (0.8 mg/kg·d) from gestational day 9 to 20. Results showed that dexamethasone increased maternal serum total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C) levels, as well as placental cholesterol synthesis and TC concentration, while reduced fetal birth weight, and serum TC, HDL-C and LDL-C levels. Meanwhile, the expression of placental cholesterol transporters, including low-density lipoprotein receptor (LDLR), scavenger receptor class B type I (SR-B1) and ATP-binding cassette transporter A1 and G1 (ABCA1 and ABCG1) were decreased by dexamethasone. Furthermore, the expression of glucocorticoid receptor (GR) and histone deacetylase 3 (HDAC3) were increased, while the H3K9ac and expression levels of liver X receptor α (LXRα) promoter were reduced. In human trophoblast cell line (BeWo), dexamethasone concentration-dependently decreased the expression levels of LDLR, SR-B1, ABCA1, ABCG1 as well as LXRα. Dexamethasone (2500 nM) induced GR translocation into nucleus and recruited HDAC3. Furthermore, LXRα agonist and GR inhibitor reversed respectively dexamethasone-induced the expression inhibitions of cholesterol transporter and LXRα, and HDAC3 siRNA reversed the H3K9ac level of LXRα promoter and its expression. Together, dexamethasone impaired placental cholesterol transport and eventually decreased fetal cholesterol levels, which is related to the down-regulation of LXRα mediated by GR/HDAC3/H3K9ac signaling.

Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development

This review focuses on one family of the known cAMP receptors, the exchange proteins directly activated by cAMP (EPACs), also known as the cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs). Although EPAC proteins are fairly new additions to the growing list of cAMP effectors, and relatively "young" in the cAMP discovery timeline, the significance of an EPAC presence in different cell systems is extraordinary. The study of EPACs has considerably expanded the diversity and adaptive nature of cAMP signaling associated with numerous physiological and pathophysiological responses. This review comprehensively covers EPAC protein functions at the molecular, cellular, physiological, and pathophysiological levels; and in turn, the applications of employing EPAC-based biosensors as detection tools for dissecting cAMP signaling and the implications for targeting EPAC proteins for therapeutic development are also discussed.

p45 NF-E2 regulates syncytiotrophoblast differentiation by post-translational GCM1 modifications in human intrauterine growth restriction

Placental insufficiency jeopardizes prenatal development, potentially leading to intrauterine growth restriction (IUGR) and stillbirth. Surviving fetuses are at an increased risk for chronic diseases later in life. IUGR is closely linked with altered trophoblast and placental differentiation. However, due to a paucity of mechanistic insights, suitable biomarkers and specific therapies for IUGR are lacking. The transcription factor p45 NF-E2 (nuclear factor erythroid derived 2) has been recently found to regulate trophoblast differentiation in mice. The absence of p45 NF-E2 in trophoblast cells causes IUGR and placental insufficiency in mice, but mechanistic insights are incomplete and the relevance of p45 NF-E2 for human syncytiotrophoblast differentiation remains unknown. Here we show that p45 NF-E2 negatively regulates human syncytiotrophoblast differentiation and is associated with IUGR in humans. Expression of p45 NF-E2 is reduced in human placentae complicated with IUGR compared with healthy controls. Reduced p45 NF-E2 expression is associated with increased syncytiotrophoblast differentiation, enhanced glial cells missing-1 (GCM1) acetylation and GCM1 desumoylation in IUGR placentae. Induction of syncytiotrophoblast differentiation in BeWo and primary villous trophoblast cells with 8-bromo-adenosine 3',5'-cyclic monophosphate (8-Br-cAMP) reduces p45 NF-E2 expression. Of note, p45 NF-E2 knockdown is sufficient to increase syncytiotrophoblast differentiation and GCM1 expression. Loss of p45 NF-E2 using either approach resulted in CBP-mediated GCM1 acetylation and SENP-mediated GCM1 desumoylation, demonstrating that p45 NF-E2 regulates post-translational modifications of GCM1. Functionally, reduced p45 NF-E2 expression is associated with increased cell death and caspase-3 activation in vitro and in placental tissues samples. Overexpression of p45 NF-E2 is sufficient to repress GCM1 expression, acetylation and desumoylation, even in 8-Br-cAMP exposed BeWo cells. These results suggest that p45 NF-E2 negatively regulates differentiation and apoptosis activation of human syncytiotrophoblast by modulating GCM1 acetylation and sumoylation. These studies identify a new pathomechanism related to IUGR in humans and thus provide new impetus for future studies aiming to identify new biomarkers and/or therapies of IUGR.

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.