The HAND1 basic helix-loop-helix transcription factor regulates trophoblast differentiation via multiple mechanisms

Human Reproduction and Disturbed Genomic Imprinting

Genomic imprinting is a specific mode of gene regulation which particularly accounts for the factors involved in development. Its disturbance affects the fetus, the course of pregnancy and even the health of the mother. In children, aberrant imprinting signatures are associated with imprinting disorders (ImpDis). These alterations also affect the function of the placenta, which has consequences for the course of the pregnancy. The molecular causes of ImpDis comprise changes at the DNA level and methylation disturbances (imprinting defects/ImpDefs), and there is an increasing number of reports of both pathogenic fetal and maternal DNA variants causing ImpDefs. These ImpDefs can be inherited, but prediction of the pregnancy complications caused is difficult, as they can cause miscarriages, aneuploidies, health issues for the mother and ImpDis in the child. Due to the complexity of imprinting regulation, each pregnancy or patient with suspected altered genomic imprinting requires a specific workup to identify the precise molecular cause and also careful clinical documentation. This review will cover the current knowledge on the molecular causes of aberrant imprinting signatures and illustrate the need to identify this basis as the prerequisite for personalized genetic and reproductive counselling of families.

Transcriptome changes associated with elongation of bovine conceptuses I: Differentially expressed transcripts in the conceptus on day 17 after insemination

The objective was to characterize transcriptome changes associated with elongation in bovine conceptuses during preimplantation stages. Nonlactating Holstein cows were euthanized 17 d after artificial insemination (AI) and the uterine horn ipsilateral to the CL was flushed with saline solution. Recovered conceptuses were classified as small (1.2 to 6.9 cm; n = 9), medium (10.5 to 16.0 cm; n = 9), or large (18.0 to 26.4 cm; n = 10). Total mRNA was extracted and subjected to transcriptome analyses using the Affymetrix Gene Chip Bovine array. Data were normalized using the GCRMA method and analyzed by robust regression using the Linear Models for Microarray library within Bioconductor in R. Transcripts with P ≤ 0.05 after adjustment for false discovery rate and fold change ≥1.5 were considered differentially expressed. Functional analyses were conducted using the Ingenuity Pathway Analysis platform. Comparisons between large versus small (LvsS), large versus medium (LvsM), and medium versus small (MvsS) conceptuses yielded a total of 634, 240, and 63 differentially expressed transcripts, respectively. Top canonical pathways of known involvement with embryo growth that were upregulated in large conceptuses included actin cytoskeleton (LvsS), integrin signaling (LvsS and LvsM), ephrin receptor (LvsS), mesenchymal transition by growth factor (LvsM), and regulation of calpain protease (LvsS). Transcripts involved with lipid metabolism pathways (LXR/RXR, FXR/RXR, hepatic fibrosis) were associated with the LvsS and LvsM, and some transcripts such as APOC2, APOH, APOM, RARA, RBP4, and PPARGC1A, were involved in these pathways. An overall network summary associated biological downstream effects of invasion of cells, proliferation of embryonic cells, and inhibition of organismal death in the LvsS. In conclusion, differently expressed transcripts in the LvsS comparison were associated with the cell growth, adhesion, and organismal development, although part of these findings could be attributed to differences in circulatory concentrations of progesterone of the cows that bore large and small conceptuses. The large and medium conceptuses developed under similar concentrations of progesterone and presented 240 differently expressed transcripts, associated with cell differentiation, metabolite regulation, and other biological processes.

Acquisition of neural fate by combination of BMP blockade and chromatin modification

Neural induction is a process where naive cells are converted into committed cells with neural characteristics, and it occurs at the earliest step during embryogenesis. Although the signaling molecules and chromatin remodeling for neural induction have been identified, the mutual relationships between these molecules are yet to be fully understood. By taking advantage of the neural differentiation system of mouse embryonic stem (ES) cells, we discovered that the BMP signal regulates the expression of several polycomb repressor complex (PRC) component genes. We particularly focused on Polyhomeotic Homolog 1 (Phc1) and established Phc1-knockout (Phc1-KO) ES cells. We found that Phc1-KO failed to acquire the neural fate, and the cells remained in pluripotent or primitive non-neural states. Chromatin accessibility analysis suggests that Phc1 is essential for chromatin packing. Aberrant upregulation of the BMP signal was confirmed in the Phc1 homozygotic mutant embryos. Taken together, Phc1 is required for neural differentiation through epigenetic modification.

Hypoplastic Left Heart Syndrome: Signaling & Molecular Perspectives, and the Road Ahead

Hypoplastic left heart syndrome (HLHS) is a lethal congenital heart disease (CHD) affecting 8-25 per 100,000 neonates globally. Clinical interventions, primarily surgical, have improved the life expectancy of the affected subjects substantially over the years. However, the etiological basis of HLHS remains fundamentally unclear to this day. Based upon the existing paradigm of studies, HLHS exhibits a multifactorial mode of etiology mediated by a complicated course of genetic and signaling cascade. This review presents a detailed outline of the HLHS phenotype, the prenatal and postnatal risks, and the signaling and molecular mechanisms driving HLHS pathogenesis. The review discusses the potential limitations and future perspectives of studies that can be undertaken to address the existing scientific gap. Mechanistic studies to explain HLHS etiology will potentially elucidate novel druggable targets and empower the development of therapeutic regimens against HLHS in the future.

Detection of Math6-Expressing Cell Types in Murine Placenta

The transcription factor Math6, mouse atonal homolog 6, belongs to the family of highly conserved basic helix-loop-helix transcription factors. It plays an important role in embryonic development and shows a wide expression pattern in murine tissues. The placenta, as a life-sustaining transient organ for the fetus, also depends on the expression of Math6. The adverse effects of deleting Math6 in mice, leading to deficient placental development and pregnancy loss, have already been demonstrated by us. Until now, detailed investigations regarding the specific mechanisms underlying the improper placental development in these murine mutants have failed, as the Math6 expression could not be confined to a specific cell type due to the lack of a highly specific Math6 antibody. To circumvent this problem, we used transgenic mice, where Math6 is marked with a Flag sequence that functions as a specific epitope. Tissues from these transgenic mice were used to establish immunohistochemical staining and fluorescence-activated cell sorting (FACS). The establishment of these methods yielded initial findings pertaining to the identification of Math6-expressing cell types and their localization. Our results reveal that Math6 shows a wide expression pattern in both maternal and fetal components of the murine placenta. It shows expression in various cell types, but predominantly in trophoblast giant cells, endothelial cells and macrophages. The largest subpopulation that we detected in the group of Math6-positive cells were identified as DBA+ uterine natural killer cells. These findings reveal information and a chance for further investigation on the involvement of Math6 in placental development and the molecular pathomechanisms of spontaneous abortion.

In Vitro Embryogenesis and Gastrulation Using Stem Cells in Mice and Humans

During early mammalian embryonic development, fertilized one-cell embryos develop into pre-implantation blastocysts and subsequently establish three germ layers through gastrulation during post-implantation development. In recent years, stem cells have emerged as a powerful tool to study embryogenesis and gastrulation without the need for eggs, allowing for the generation of embryo-like structures known as synthetic embryos or embryoids. These in vitro models closely resemble early embryos in terms of morphology and gene expression and provide a faithful recapitulation of early pre- and post-implantation embryonic development. Synthetic embryos can be generated through a combinatorial culture of three blastocyst-derived stem cell types, such as embryonic stem cells, trophoblast stem cells, and extraembryonic endoderm cells, or totipotent-like stem cells alone. This review provides an overview of the progress and various approaches in studying in vitro embryogenesis and gastrulation in mice and humans using stem cells. Furthermore, recent findings and breakthroughs in synthetic embryos and gastruloids are outlined. Despite ethical considerations, synthetic embryo models hold promise for understanding mammalian (including humans) embryonic development and have potential implications for regenerative medicine and developmental research.

Trophoblast Differentiation: Mechanisms and Implications for Pregnancy Complications

Placental development is a tightly controlled event, in which cell expansion from the trophectoderm occurs in a spatiotemporal manner. Proper trophoblast differentiation is crucial to the vitality of this gestational organ. Obstructions to its development can lead to pregnancy complications, such as preeclampsia, fetal growth restriction, and preterm birth, posing severe health risks to both the mother and offspring. Currently, the only known treatment strategy for these complications is delivery, making it an important area of research. The aim of this review was to summarize the known information on the development and mechanistic regulation of trophoblast differentiation and highlight the similarities in these processes between the human and mouse placenta. Additionally, the known biomarkers for each cell type were compiled to aid in the analysis of sequencing technologies.

The trophoblast giant cells of cricetid rodents

Giant cells are a prominent feature of placentation in cricetid rodents. Once thought to be maternal in origin, they are now known to be trophoblast giant cells (TGCs). The large size of cricetid TGCs and their nuclei reflects a high degree of polyploidy. While some TGCs are found at fixed locations, others migrate throughout the placenta and deep into the uterus where they sometimes survive postpartum. Herein, we review the distribution of TGCs in the placenta of cricetids, including our own data from the New World subfamily Sigmodontinae, and attempt a comparison between the TGCs of cricetid and murid rodents. In both families, parietal TGCs are found in the parietal yolk sac and as a layer between the junctional zone and decidua. In cricetids alone, large numbers of TGCs, likely from the same lineage, accumulate at the edge of the placental disk. Common to murids and cricetids is a haemotrichorial placental barrier where the maternal-facing layer consists of cytotrophoblasts characterized as sinusoidal TGCs. The maternal channels of the labyrinth are supplied by trophoblast-lined canals. Whereas in the mouse these are lined largely by canal TGCs, in cricetids canal TGCs are interspersed with syncytiotrophoblast. Transformation of the uterine spiral arteries occurs in both murids and cricetids and spiral artery TGCs line segments of the arteries that have lost their endothelium and smooth muscle. Since polyploidization of TGCs can amplify selective genomic regions required for specific functions, we argue that the TGCs of cricetids deserve further study and suggest avenues for future research.

The developmental regulator HAND1 inhibits gastric carcinogenesis through enhancing ER stress apoptosis via targeting CHOP and BAK which is augmented by cisplatin

Epigenetic disruption of tumor suppressor genes, particularly aberrant CpG methylation, plays a crucial role in gastric cancer (GC) pathogenesis. Through CpG methylome and expression profiling, a developmental transcription factor - Hand-And-Neural-crest-Derivative-expressed 1 (HAND1), was identified methylated and downregulated in GC. However, its role and underlying mechanisms in GC progression are poorly understood. Here, we show that HAND1 was frequently downregulated in GC by promoter methylation, and significantly correlated with tumor progression and poor prognosis of GC patients. High expression of HAND1 in GC patients was associated with significantly higher 5-year overall survival rates. Ectopic expression of HAND1 inhibited GC cell growth and migration in vitro and in vivo. HAND1 expression increased ROS levels and cytosolic Ca²⁺ concentration, enhanced cisplatin-induced apoptosis through endoplasmic reticulum (ER) stress/mitochondria-mediated apoptosis. Knockdown of CHOP and BAK attenuated HAND1-induced cell apoptosis. Overexpression of CHOP increased BAK expression. HAND1 interacts with CHOP, also directly binds to CHOP and BAK promoters and positively regulates BAK transcription. Thus, the present study demonstrates that HAND1 is a tumor suppressor gene methylated in GC, induces ER stress and apoptosis via CHOP and BAK, which is augmented by cisplatin. Low HAND1 expression is an independent poor prognostic factor for GC. The tumor-specific methylation of HAND1 promoter could be a candidate biomarker for GC.

Impact of Prenatal Nicotine Exposure on Placental Function and Respiratory Neural Network Development

Smoking during pregnancy is associated with multiple undesirable outcomes in infants, such as low birth weight, increased neonatal morbidity and mortality, and catastrophic conditions like sudden infant death syndrome (SIDS). Nicotine, the most addictive and teratogenic substance in tobacco smoke, reaches and crosses the placenta and can be accumulated in the amniotic fluid and distributed by fetal circulation, altering the cholinergic transmission by acting on the nicotinic acetylcholine receptors (nAChRs) expressed from very early gestational stages in the placenta and fetal tissue. Because nAChRs influence the establishment of feto-maternal circulation and the emergence of neuronal networks, prenatal nicotine exposure can lead to multiple alterations in newborns. In this mini-review, we discuss the undeniable effects of nicotine in the placenta and the respiratory neural network as examples of how prenatal nicotine and smoking exposition can affect brain development because dysfunction in this network is involved in SIDS etiology.

Adgrg1 is a new transcriptional target of Hand1 during trophoblast giant cell differentiation

The placenta, forming the maternal-fetal interface, is essential for the survival and development of the fetus. It has been shown that the basic helix-loop-helix (bHLH) transcription factor Hand1 plays an important role in trophoblast giant cells (TGCs) differentiation during placental development in mice. However, the underlying molecular mechanism remains elusive. We hereby report that Adgrg1 (GPR56), a G protein coupled receptor, was a new transcriptional target of Hand1. Hand1 activated the expression of Adgrg1 by binding to its promoter region during TGCs differentiation. Double in situ hybridization revealed co-expression of Hand1 and Adgrg1 in Prl2c2⁺ TGCs located in the junctional zone of the placenta. Knockdown of Adgrg1 not only led to increased Prl2c2 expression, but also the improvement of cell migration and invasion during TGC differentiation. Moreover, the ligand of Adgrg1, Tgm2, was expressed in Prl2c2⁺ TGCs located in the placental junctional zone and Tgm2 Knockdown increased cell migration and invasion, suggesting Tgm2 is a potential ligand involved in the functions of Adgrg1 during TGC differentiation in the manners of autocrine. Collectively, these results demonstrate that Adgrg1 is a new transcriptional target of Hand1, affecting Prl2c2 expression as well as cell migration and invasion during TGCs differentiation. As a transmembrane receptor, Adgrg1 perhaps could act as a potential therapeutic target for placental-associated diseases caused by abnormal trophoblast migration and invasion, providing new insights for the preventions and therapies of placenta-related diseases.

Perinatal exposure to glyphosate-based herbicides impairs progeny health and placental angiogenesis by disturbing mitochondrial function

Glyphosate-based herbicides (GBHs) are the most widely used pesticide worldwide and can provoke placental injury. However, whether and how GBHs damage angiogenesis in the placenta is not yet known. This work evaluated the safety of glyphosate on pregnant sows based on the limit level by governments and investigated the effects and mechanism of Low-GBHs (20 mg/kg) and High-GBHs (100 mg/kg) exposure on placental angiogenesis. Results showed that gestational exposure to GBHs decreased placental vessel density and cell multiplication by interfering with the expression of VEGFA, PLGF, VEGFr2 and Hand2 (indicators of angiogenesis), which may be in relation to oxidative stress-induced disorders of mitochondrial fission and fusion as well as the impaired function of the mitochondrial respiratory chain. Additionally, GBHs destroyed barrier function and nutrient transport in the placenta, and was accompanied by jejunum oxidative stress in newborn piglets. However, GBHs exposure had no significant differences on sow reproductive performance. As a natural antioxidant, betaine treatment protected placenta and newborn piglets against GBHs-induced damage. In conclusion, GBHs impaired placental angiogenesis and function and further damaged the health of postnatal progeny, these effects may be linked to mitochondrial dysfunction. Betaine treatment following glyphosate exposure provided modest relief.

Dynamic Changes of Gene Expression in Mouse Mural Trophectoderm Regulated by Cdx2 During Implantation

Implantation of the blastocyst into the uterus is a specific and essential process for mammalian embryonic development. In mice, implantation is initiated from the mural trophectoderm of the blastocyst and the mTE controls implantation progression by acquiring the ability to attach and invade into the endometrium while differentiating into primary trophoblast giant cells. Nevertheless, it remains largely unclear when and how the mTE differentiates and acquires this ability during implantation. Here, by RNA sequencing analysis with the pre- and peri-implantation mTE, we show that the mTE undergoes stage-specific and dynamic changes of gene expression during implantation. We also reveal that the mTE begins down-regulating Cdx2 and up-regulating differentiation marker genes during the peri-implantation stage. In addition, using trophectoderm (TE) -specific lentiviral vector-mediated gene transduction, we demonstrate that TE-specific Cdx2 overexpression represses differentiation of the mTE into the primary trophoblast giant cells. Moreover, we reveal that TE-specific Cdx2 overexpression also represses the up-regulation of cell adhesion- and migration-related genes, including Slc6a14, Slc16a3, Itga7, Itgav and Itgb3, which are known to regulate migration of trophectoderm cells. In particular, the expression of Itgb3, an integrin subunit gene, exhibits high inverse correlation with that of Cdx2 in the TE. Reflecting the down-regulation of the genes for TE migration, TE-specific Cdx2 overexpression causes suppression of the blastocyst outgrowth in vitro and abnormal progression of implantation in vivo. Thus, our results specify the time-course changes of global gene expression in the mTE during implantation and uncover the significance of Cdx2 down-regulation for implantation progression.

Padi2/3 Deficiency Alters the Epigenomic Landscape and Causes Premature Differentiation of Mouse Trophoblast Stem Cells

Histone citrullination is a relatively poorly studied epigenetic modification that involves the irreversible conversion of arginine residues into citrulline. It is conferred by a small family of enzymes known as protein arginine deiminases (PADIs). PADI function supports the pluripotent state of embryonic stem cells, but in other contexts, also promotes efficient cellular differentiation. In the current study, we sought to gain deeper insights into the possible roles of PADIs in mouse trophoblast stem cells (TSCs). We show that Padi2 and Padi3 are the most highly expressed PADI family members in TSCs and are rapidly down-regulated upon differentiation. Padi2/3 double knockout (DKO) TSCs express lower levels of stem cell transcription factors CDX2 and SOX2 and are prone to differentiate into extremely large trophoblast giant cells, an effect that may be mediated by centrosome duplication defects. Interestingly, Padi2/3 DKO TSCs display alterations to their epigenomic landscape, with fewer H3K9me3-marked chromocentric foci and globally reduced 5-methylcytosine levels. DNA methylation profiling identifies that this effect is specifically evident at CpG islands of critical trophoblast genes, such as Gata3, Peg3, Socs3 and Hand1. As a consequence of the hypomethylated state, these factors are up-regulated in Padi2/3 DKO TSCs, driving their premature differentiation. Our data uncover a critical epigenetic role for PADI2/3 in safeguarding the stem cell state of TSCs by modulating the DNA methylation landscape to restrict precocious trophoblast differentiation.

Maternal exposure to ambient PM2.5 causes fetal growth restriction via the inhibition of spiral artery remodeling in mice

BACKGROUND

Maternal exposure to ambient fine particulate matters (PM_2.5) is associated with low birth weight (LBW) in offspring, but the underlying biological mechanisms are not yet fully understood. As the bridge that connects mother and fetus, the placenta plays a crucial role in fetal development by providing the fetus with nutrients and oxygen. However, whether PM_2.5 exposure would impact the placental development and the related mechanisms are unclear.

RESULTS

In the present study, female C57Bl/6j mice were exposed to filtered air (FA) or concentrated ambient PM_2.5 (CAP) during pregestational and gestational periods, and the fetal development and placental structure were investigated. Our results showed that maternal exposure to CAP induced fetal growth restriction (FGR) and LBW. The placenta from CAP-exposed mice exhibited abnormal development including significant decrease of surface area, smaller junctional zone and impaired spiral artery remodeling. Meanwhile, CAP exposure altered trophoblast lineage differentiation and disrupted the balance between angiogenic and angiostatic factors in placenta. In addition, the inflammatory cytokines levels in lung, placenta and serum were significantly increased after ambient PM_2.5 exposure.

CONCLUSION

Our findings indicate that maternal exposure to PM_2.5 disrupts normal structure and spiral artery remodeling of placenta and further induces FGR and LBW. This effect may be caused by the placental inflammation response subsequent to the pulmonary and systemic inflammation induced by ambient PM_2.5 exposure.

Development of an Improved in vitro Model of Bovine Trophectoderm Differentiation

The mechanisms regulating early stages of placentation and trophectoderm differentiation in the ruminant conceptus remain poorly understood. Here we present a model of trophectoderm (TE) differentiation in vitro from outgrowths of individual in vitro derived embryos. Cell outgrowths expressed markers of mononucleate (MNC) and binucleate (BNC) TE cells. The percentage of BNC ranged from 14 to 39% in individual outgrowths as determined by flow cytometry. Pregnancy-associated glycoproteins (PAGs), produced by BNC, were measured in culture media on days 35 to 54. Continuous secretion of PAGs was observed and indicative of BNC functionality. Gene expression was evaluated in 20 embryo cell outgrowths derived from two different sires. Expression of HAND1, which is involved in TE differentiation, and CSH2, a BNC-specific gene, was altered in cell outgrowths between the two sires tested. Single-cell RNA-seq analysis of day 40 TE cell outgrowths revealed 11 distinct cell populations, with specific clusters genes involved in TE lineage specification, proliferation, and differentiation. In addition, whole -RNAseq analysis was performed in day 35 and 40 TE cell outgrowths and confirmed sustained expression of genes expressed by BNC, such as CSH2 and some PAGs. The developed in vitro bovine embryo outgrowth culture found evidence for MNC and BNC differentiation and continuous production of PAGs, recapitulating key features of early bovine placenta development. This model can be used to understand the developmental biology of TE cells, provide insights into paternal influences on TE differentiation, and impact our understanding of early pregnancy loss in cattle.

Vaginal Exposure to Candida albicans During Early Gestation Results in Adverse Pregnancy Outcomes via Inhibiting Placental Development

Vulvovaginal candidiasis (VVC) is considered the second most common cause of vaginitis after bacterial vaginosis and the most common lower genital tract infection during pregnancy. Candida albicans (C. albicans), an opportunistic pathogen, is the major species causing VVC. Recently, increasing researches have shown that lower reproductive tract infection during pregnancy can lead to various adverse pregnancy outcomes. However, the underlying mechanisms are not fully understood. Hence, we successfully established a mouse model of vaginal C. albicans infection and characterized the adverse pregnancy outcomes. C. albicans infection strikingly increased abortion rate and decreased litter size. Further analysis of placental development demonstrated that placental structure was abnormal, including that the area of spongiotrophoblast (Spo) and labyrinth (Lab) was reduced, and the formation of placental vessel was decreased in Lab zone. Accordingly, the expression of marker genes during placental development was downregulated. Collectively, the above findings revealed that vaginal C. albicans infection during pregnancy can inhibit placental development and ultimately lead to adverse pregnancy outcomes. This study enhances our comprehension of the effect of VVC on pregnancy, and placental dysplasia as a feasible orientation to explore VVC during pregnancy.

Homodimeric and Heterodimeric Interactions among Vertebrate Basic Helix-Loop-Helix Transcription Factors

The basic helix–loop–helix transcription factor (bHLH TF) family is involved in tissue development, cell differentiation, and disease. These factors have transcriptionally positive, negative, and inactive functions by combining dimeric interactions among family members. The best known bHLH TFs are the E-protein homodimers and heterodimers with the tissue-specific TFs or ID proteins. These cooperative and dynamic interactions result in a complex transcriptional network that helps define the cell’s fate. Here, the reported dimeric interactions of 67 vertebrate bHLH TFs with other family members are summarized in tables, including specifications of the experimental techniques that defined the dimers. The compilation of these extensive data underscores homodimers of tissue-specific bHLH TFs as a central part of the bHLH regulatory network, with relevant positive and negative transcriptional regulatory roles. Furthermore, some sequence-specific TFs can also form transcriptionally inactive heterodimers with each other. The function, classification, and developmental role for all vertebrate bHLH TFs in four major classes are detailed.

Follistatin supplementation induces changes in CDX2 CpG methylation and improves in vitro development of bovine SCNT preimplantation embryos

Caudal Type Homeobox 2 (CDX2) is a key regulator of trophectoderm formation and maintenance in preimplantation embryos. We previously demonstrated that supplementation of exogenous follistatin, during in vitro culture of bovine IVF embryos, upregulates CDX2 expression, possibly, via alteration of the methylation status of CDX2 gene. Here, we further investigated the effects of exogenous follistatin supplementation on developmental competence and CDX2 methylation in bovine somatic cell nuclear transfer (SCNT) embryos. SCNT embryos were cultured with or without follistatin for 72h, then transferred into follistatin free media until d7 when blastocysts were collected and subjected to CDX2 gene expression and DNA methylation analysis for CDX2 regulatory regions by bisulfite sequencing. Follistatin supplementation significantly increased both blastocyst development as well as blastocyst CDX2 mRNA expression on d7. Three different CpG rich fragments within the CDX2 regulatory elements; proximal promoter (fragment P1, -1644 to -1180; P2, -305 to +126) and intron 1 (fragment I, + 3030 to + 3710) were identified and selected for bisulfite sequencing analysis. This analysis showed that follistatin treatment induced differential methylation (DM) at specific CpG sites within the analyzed fragments. Follistatin treatment elicited hypomethylation at six CpG sites at positions -1374, -279, -163, -23, +122 and +3558 and hypermethylation at two CpG sites at positions -243 and +20 in promoter region and first intron of CDX2 gene. Motif analysis using MatInspector revealed that differentially methylated CpG sites are putative binding sites for key transcription factors (TFs) known to regulate Cdx2 expression in mouse embryos and embryonic stem cells including OCT1, AP2F, KLF and P53, or TFs that have indirect link to CDX2 regulation including HAND and NRSF. Collectively, results of the present study together with our previous findings in IVF embryos support the hypothesis that alteration of CDX2 methylation is one of the epigenetic mechanisms by which follistatin may regulates CDX2 expression in preimplantation bovine embryos.

Bmp Signaling Regulates Hand1 in a Dose-Dependent Manner during Heart Development

The bone morphogenetic protein (Bmp) signaling pathway and the basic helix–loop–helix (bHLH) transcription factor Hand1 are known key regulators of cardiac development. In this study, we investigated the Bmp signaling regulation of Hand1 during cardiac outflow tract (OFT) development. In Bmp2 and Bmp4loss-of-function embryos with varying levels of Bmp in the heart, Hand1 is sensitively decreased in response to the dose of Bmp expression. In contrast, Hand1 in the heart is dramatically increased in Bmp4 gain-of-function embryos. We further identified and characterized the Bmp/Smad regulatory elements in Hand1. Combined transfection assays and chromatin immunoprecipitation (ChIP) experiments indicated that Hand1 is directly activated and bound by Smads. In addition, we found that upon the treatment of Bmp2 and Bmp4, P19 cells induced Hand1 expression and favored cardiac differentiation. Together, our data indicated that the Bmp signaling pathway directly regulates Hand1 expression in a dose-dependent manner during heart development.

Superovulation with human chorionic gonadotropin (hCG) trigger and gonadotropin releasing hormone agonist (GnRHa) trigger differentially alter essential angiogenic factors in the endometrium in a mouse ART model†

Gonadotropin-releasing hormone agonists (GnRHa) are used as an alternative to human chorionic gonadotropin (hCG) to trigger ovulation and decrease the risk of ovarian hyperstimulation syndrome. GnRHa is less potent at inducing ovarian vascular endothelial growth factor (VEGF), but may also affect endometrial angiogenesis and early placental development. In this study, we explore the effect of superovulation on endometrial angiogenesis during critical periods of gestation in a mouse model. We assigned female mice to three groups: natural mating or mating following injection with equine chorionic gonadotropin and trigger with GnRHa or hCG trigger. Females were killed prior to implantation (E3.5), post-implantation (E7.5), and at midgestation (E10.5), and maternal serum, uterus, and ovaries were collected. During peri-implantation, endometrial Vegfr1 and Vegfr2 mRNA were significantly increased in the GnRHa trigger group (P < 0.02) relative to the hCG group. Vegfr1 is highly expressed in the endometrial lining and secretory glands immediately prior to implantation. At E7.5, the ectoplacental cone expression of Vegfa and its receptor, Vegfr2, was significantly higher in the hCG trigger group compared to the GnRHa group (P < 0.05). Soluble VEGFR1 and free VEGFA were much higher in the serum of mice exposed to the hCG trigger compared to GnRHa group. At midgestation, there was significantly more local Vegfa expression in the placenta of mice triggered with hCG. GnRHa and hCG triggers differentially disrupt the endometrial expression of key angiogenic factors during critical periods of mouse gestation. These results may have significant implications for placental development and neonatal outcomes following human in vitro fertilization.

Human HAND1 Inhibits the Conversion of Cholesterol to Steroids in Trophoblasts

Steroidogenesis from cholesterol in placental trophoblasts is fundamentally involved in the establishment and maintenance of pregnancy. The transcription factor gene Heart And Neural crest Derivatives expressed 1 (Hand1) promotes differentiation of mouse trophoblast giant cells. However, the role of HAND1 in human trophoblasts remains unknown. Here, we report that HAND1 inhibits human trophoblastic progesterone (P4) and estradiol (E2) from cholesterol through down-regulation of the expression of steroidogenic enzymes including aromatase, P450 cholesterol side-chain cleavage enzyme (P450scc) and 3β-hydroxysteroid dehydrogenase type 1 (3β-HSD1). Mechanically, while HAND1 inhibits transcription of aromatase by directly binding to aromatase gene promoter, it restrains transcription of P450scc by up-regulation of the methylation status of P450scc gene promoter through its binding to ALKBH1, a demethylase. Unlike aromatase and P450scc, HAND1 decreases 3β-HSD1 mRNA levels by reduction of its RNA stability through binding to and subsequent destabilization of protein HuR. Finally, HAND1 suppresses circulating P4 and E2 levels derived from JEG-3 xenograft, and attenuates uterine response to P4 and E2. Thus, our results uncover a hitherto uncharacterized role of HAND1 in regulation of cholesterol metabolism in human trophoblasts, which may help pinpoint the underlying mechanisms involved in supporting the development and physiological function of the human placenta.

Amphiregulin stimulates human chorionic gonadotropin expression by inducing ERK1/2-mediated ID3 expression in trophoblast cells

INTRODUCTION

The human chorionic gonadotropin (hCG) is a dimer consisting of an α subunit and a β subunit which is encoded by the CGB gene and is unique to hCG. hCG is a hormone mainly synthesized by syncytiotrophoblast cells in the placenta, plays a critical role in stimulating progesterone production that is necessary for maintaining normal pregnancy in the early stage. Epidermal growth factor receptor (EGFR) belongs to the receptor tyrosine kinase family which has been shown to regulate various physiological and pathological events. In human chorionic villi and amniotic fluid, amphiregulin (AREG) is reported to be the most abundant EGFR ligand and can stimulate hCG expression. However, the underlying mechanism remains unknown.

METHODS

We use BeWo cells, the commonly used cell model for the hCG production of trophoblast cells, as an in vitro model. The effects of AREG on CGB expression and hCG secretion as well as the underlying mechanisms were explored by a series of in vitro experiments.

RESULTS

We show that treatment with AREG stimulates CGB expression and hCG secretion. Using pharmacological inhibitors, we show that the stimulatory effects of AREG on CGB expression and hCG secretion are mediated by the EGFR-activated ERK1/2 signaling pathways. In addition, the expression of inhibitor of DNA-binding protein 3 (ID3) is upregulated by AREG. Knockdown of ID3 attenuates the AREG-induced upregulation of CGB expression and hCG secretion.

DISCUSSION

This study provides important insights into the molecular mechanisms that mediate AREG-induced upregulation of hCG production in human trophoblast cells which may lead to the development of alternative therapeutic approaches for the treatment of placental diseases.

RNA-Seq reveals changes in human placental metabolism, transport and endocrinology across the first-second trimester transition

The human placenta is exposed to major environmental changes towards the end of the first trimester associated with full onset of the maternal arterial placental circulation. Changes include a switch from histotrophic to hemotrophic nutrition, and a threefold rise in the intraplacental oxygen concentration. We evaluated their impact on trophoblast development and function using RNA-sequencing (RNA-Seq) and DNA-methylation analyses performed on the same chorionic villous samples at 7-8 (n=8) and 13-14 (n=6) weeks of gestation. Reads were adjusted for fetal sex. Most DEGs were associated with protein processing in the endoplasmic reticulum (ER), hormone secretion, transport, extracellular matrix, vasculogenesis, and reactive oxygen species metabolism. Transcripts higher in the first trimester were associated with synthesis and ER processing of peptide hormones, and glycolytic pathways. Transcripts encoding proteins mediating transport of oxygen, lipids, protein, glucose, and ions were significantly increased in the second trimester. The motifs of CBX3 and BCL6 were significantly overrepresented, indicating the involvement of these transcription factor networks in the regulation of trophoblast migration, proliferation and fusion. These findings are consistent with a high level of cell proliferation and hormone secretion by the early placenta to secure implantation in a physiological low-oxygen environment.

Overexpression of miR-210-3p Impairs Extravillous Trophoblast Functions Associated with Uterine Spiral Artery Remodeling

Hsa-miR-210-3p has been reported to be upregulated in preeclampsia (PE); however, the functions of miR-210-3p in placental development are not fully understood, and, consequently, miR-210-3p’s role in the pathogenesis of PE is still under investigation. In this study, we found that overexpression of miR-210-3p reduced trophoblast migration and invasion, extravillous trophoblast (EVT) outgrowth in first trimester explants, expression of endovascular trophoblast (enEVT) markers and the ability of trophoblast to form endothelial-like networks. In addition, miR-210-3p overexpression significantly downregulated the mRNA levels of interleukin-1B and -8, as well as CXC motif ligand 1. These cytokines have been suggested to play a role in EVT invasion and the recruitment of immune cells to the spiral artery remodeling sites. We also showed that caudal-related homeobox transcription factor 2 (CDX2) is targeted by miR-210-3p and that CDX2 downregulation mimicked the observed effects of miR-210-3p upregulation in trophoblasts. These findings suggest that miR-210-3p may play a role in regulating events associated with enEVT functions and its overexpression could impair spiral artery remodeling, thereby contributing to PE.

Elucidating evolutionarily conserved mechanisms of diapause regulation using an in silico approach

Embryonic diapause is an enigmatic phenomenon that appears in diverse species. Although regulatory mechanisms have been established, there is much to be discovered. Herein, we have made the first comprehensive attempt to elucidate diapause regulatory mechanisms using a computational approach. We found transcription factors unique to promoters of genes in diapause species. From pathway analysis and STRING PPI networks, the signaling pathways regulated by these unique transcription factors were identified. The pathways were then consolidated into a model to combine various known mechanisms of diapause regulation. This work also highlighted certain transcription factors that may act as 'master transcription factors' to regulate the phenomenon. Promoter analysis further suggested evidence for independent evolution for some of regulatory elements involved in diapause.

MicroRNA regulation of murine trophoblast stem cell self-renewal and differentiation

Post-transcriptional regulation of CDX2 and cell cycle genes by miR-290 and miR-322 clusters along with transactivation of miR-290 cluster and cyclin D1 by CDX2 equipoise trophoblast stem cell self-renewal and differentiation.

Proper placentation is fundamental to successful pregnancy. Placenta arises from differentiation of trophoblast stem (TS) cells during development. Despite being recognized as the counterpart of ES cells in placental development, the role of regulatory miRNAs in TS cell differentiation remains inadequately explored. Here, we have identified complete repertoire of microRNAs present in mouse trophoblast cells in proliferative and differentiated state. We demonstrated that two miRNA clusters, -290 and -322, displayed reciprocal expression during trophoblast differentiation. Loss of miR-290 cluster members or gain in miR-322 cluster members led to differentiation of TS cells. The trophoblast stemness factor, CDX2, transactivated the miR-290 cluster and Cyclin D1. MiR-290 cluster members repressed cell cycle repressors, P21, P27, WEE1, RBL2, and E2F7, in TS cells. MiR-322 cluster members repressed the cell cycle activators, CYCLIN D1, CYCLIN E1, CDC25B, and CDX2, to induce differentiation. Taken together, our findings highlight the importance of posttranscriptional regulation by conserved miRNA clusters that form a regulatory network with CDX2, cell cycle activators, and repressors in equipoising TS cell self-renewal and differentiation.

Persistent Human KIT Receptor Signaling Disposes Murine Placenta to Premature Differentiation Resulting in Severely Disrupted Placental Structure and Functionality

Activating mutations in the human KIT receptor is known to drive severe hematopoietic disorders and tumor formation spanning various entities. The most common mutation is the substitution of aspartic acid at position 816 to valine (D816V), rendering the receptor constitutively active independent of ligand binding. As the role of the KIT receptor in placental signaling cascades is poorly understood, we analyzed the impact of KIT^D816V expression on placental development using a humanized mouse model. Placentas from KIT^D816V animals present with a grossly changed morphology, displaying a reduction in labyrinth and spongiotrophoblast layer and an increase in the Parietal Trophoblast Giant Cell (P-TGC) layer. Elevated differentiation to P-TGCs was accompanied with reduced differentiation to other Trophoblast Giant Cell (TGC) subtypes and by severe decrease in proliferation. The embryos display growth retardation and die in utero. KIT^D816V-trophoblast stem cells (TSC) differentiate much faster compared to wild type (WT) controls. In undifferentiated KIT^D816V-TSCs, levels of Phosphorylated Extracellular-signal Regulated Kinase (P-ERK) and Phosphorylated Protein Kinase B (P-AKT) are comparable to wildtype cultures differentiating for 3–6 days. Accordingly, P-TGC markers Placental Lactogen 1 (PL1) and Proliferin (PLF) are upregulated as well. The results reveal that KIT signaling orchestrates the fine-tuned differentiation of the placenta, with special emphasis on P-TGC differentiation. Appropriate control of KIT receptor action is therefore essential for placental development and nourishment of the embryo.

Autophagy regulates abnormal placentation induced by folate deficiency in mice

Folate deficiency has been linked to a wide range of pregnancy disorders. Most research about folate-deficiency has focused on the embryo itself, little attention has been paid to possible effects on the placenta. According to our results, the morphology of the placenta, endocrine function, and the expression of genes involved in placental differentiation were all abnormal in folate-deficient mice on days 10, 12, and 14 of pregnancy. Similar results were found in human placenta explants cultured in folate-deficient medium. Autophagy is an inducible catabolic process activated by external nutrients starvation. Here we explored further, whether autophagy was involved in the abnormal placentation caused by folate-deficiency. The aberrant number of autophagosomes measured by transmission electron microscopy and the deviant expression of autophagy-related markers showed a disordered autophagy in placentas under conditions of folate-deficiency in vivo and in vitro dual-fluorescence mRFP-eGFP-LC3 analysis indicated enhanced autophagy was detected in HTR8/SVneo cells incubated in folate-deficient medium. Importantly, the placentation impairment in mice and human placenta explants could be recovered by inhibiting placental autophagy using 3-MA. In addition, the apoptosis and invasive capability of HTR8/SVneo cells were obviously suppressed by folate deficiency but notably elevated by 3-MA. These data suggest that folate deficiency can impair placentation and autophagy is a key factor in this. However, the signal pathway by which folate deficiency causes aberrant autophagy needs to be explored further.

Maternal exposure to CeO2NPs during early pregnancy impairs pregnancy by inducing placental abnormalities

Cerium dioxide nanoparticles (CeO₂NPs) has been widely used in many fields, and also recommended as a promising carrier for cancer targeted drugs in human medicine for its excellent properties. However, its biological safety to human health remains controversial. In this study, we propose a mouse model exposed to CeO₂NPs during early pregnancy, to clarify the effect of maternal CeO₂NPs exposure and related molecular mechanism. Pregnant mice are injected intravenously with CeO₂NPs by once a day on D5, D6, and D7. The effects of CeO₂NPs exposure on pregnancy outcomes are observed on D8, D9, D10 and D12. The results show that CeO₂NPs exposure during early pregnancy would lead to poor pregnancy outcomes. Further study find that low-quality decidualization, including the imbalance of trophoblast invasion regulators secreted by decidual cells and abnormal recruitment and differentiation of uNK cells, leads to subsequent biological negative "ripple effects", including placental dysfunction, fetal loss or growth restriction. This study broadens the understanding of the biological safety of CeO₂NPs, and provide clues for the prevention of its negative biological effects. Improving the function of uNK cells can be used as one of the therapeutic targets to prevent negative effects of CeO₂NPs on pregnancy.

Inositol 1,4,5-trisphosphate receptors are essential for fetal-maternal connection and embryo viability

Inositol 1,4,5-trisphosphate receptors (IP3Rs) are a family of intracellular Ca2+ release channels located on the ER membrane, which in mammals consist of 3 different subtypes (IP3R1, IP3R2, and IP3R3) encoded by 3 genes, Itpr1, Itpr2, and Itpr3, respectively. Studies utilizing genetic knockout mouse models have demonstrated that IP3Rs are essential for embryonic survival in a redundant manner. Deletion of both IP3R1 and IP3R2 has been shown to cause cardiovascular defects and embryonic lethality. However, it remains unknown which cell types account for the cardiovascular defects in IP3R1 and IP3R2 double knockout (DKO) mice. In this study, we generated conditional IP3R1 and IP3R2 knockout mouse models with both genes deleted in specific cardiovascular cell lineages. Our results revealed that deletion of IP3R1 and IP3R2 in cardiomyocytes by TnT-Cre, in endothelial / hematopoietic cells by Tie2-Cre and Flk1-Cre, or in early precursors of the cardiovascular lineages by Mesp1-Cre, resulted in no phenotypes. This demonstrated that deletion of both IP3R genes in cardiovascular cell lineages cannot account for the cardiovascular defects and embryonic lethality observed in DKO mice. We then revisited and performed more detailed phenotypic analysis in DKO embryos, and found that DKO embryos developed cardiovascular defects including reduced size of aortas, enlarged cardiac chambers, as well as growth retardation at embryonic day (E) 9.5, but in varied degrees of severity. Interestingly, we also observed allantoic-placental defects including reduced sizes of umbilical vessels and reduced depth of placental labyrinth in DKO embryos, which could occur independently from other phenotypes in DKO embryos even without obvious growth retardation. Furthermore, deletion of both IP3R1 and IP3R2 by the epiblast-specific Meox2-Cre, which targets all the fetal tissues and extraembryonic mesoderm but not extraembryonic trophoblast cells, also resulted in embryonic lethality and similar allantoic-placental defects. Taken together, our results demonstrated that IP3R1 and IP3R2 play an essential and redundant role in maintaining the integrity of fetal-maternal connection and embryonic viability.

Impact of maternal obesity on placental transcriptome and morphology associated with fetal growth restriction in mice

BACKGROUND

In utero exposure to obesity is consistently associated with increased risk of metabolic disease, obesity and cardiovascular dysfunction in later life despite the divergence of birth weight outcomes. The placenta plays a critical role in offspring development and long-term health, as it mediates the crosstalk between the maternal and fetal environments. However, its phenotypic and molecular modifications in the context of maternal obesity associated with fetal growth restriction (FGR) remain poorly understood.

METHODS

Using a mouse model of maternal diet-induced obesity, we investigated changes in the placental transcriptome through RNA sequencing (RNA-seq) and Ingenuity Pathway Analysis (IPA) at embryonic day (E) 19. The most differentially expressed genes (FDR < 0.05) were validated by Quantitative real-time PCR (qPCR) in male and female placentae at E19. The expression of these targets and related genes was also determined by qPCR at E13 to examine whether the observed alterations had an earlier onset at mid-gestation. Structural analyses were performed using immunofluorescent staining against Ki67 and CD31 to investigate phenotypic outcomes at both timepoints.

RESULTS

RNA-seq and IPA analyses revealed differential expression of transcripts and pathway interactions related to placental vascular development and tissue morphology in obese placentae at term, including downregulation of Muc15, Cnn1, and Acta2. Pdgfb, which is implicated in labyrinthine layer development, was downregulated in obese placentae at E13. This was consistent with the morphological evidence of reduced labyrinth zone (LZ) size, as well as lower fetal weight at both timepoints irrespective of offspring sex.

CONCLUSIONS

Maternal obesity results in abnormal placental LZ development and impaired vascularization, which may mediate the observed FGR through reduced transfer of nutrients across the placenta.

Choice of factors and medium impinge on success of ESC to TSC conversion

INTRODUCTION

The first lineage separation in mammalian development occurs when totipotent cells of the zygote give rise to the inner cell mass and the trophectoderm. The lineages are strictly separated by an epigenetic barrier. In vitro derivatives of these lineages embryonic stem cells (ESC) and trophoblast stem cells (TSC) are used to study the requirements needed to overcome the barrier in ESC to TSC conversion approaches.

METHODS

Different combinations of TSC transcription factors were induced in ESC for three days. Cells were kept in TS medium with fetal bovine serum (FBS) or the chemically defined TX medium. Obtained cells were analysed for OCT4 levels, TSC surface marker levels, expression of TSC markers and methylation status of Elf5, Oct4 and Nanog promoters. Further, long-term culture stability and in vitro and in vivo differentiation was tested.

RESULTS

Overexpression of Gata3, Eomes, Tfap2c, Ets2 and Cdx2 in ESC resulted in induction of TSC fate. Overexpression of Cdx2 or four factors (Gata3, Eomes, Tfap2c and Ets2) resulted in complete conversion only when cells were cultured in TX medium. The obtained induced TSC (iTSC) display characteristics of bona fide TSC in terms of marker expression and promoter methylation patterns. The generated converted cells were shown to display self-renewal and to be capable to differentiate into TSC derivatives in vitro and in vivo.

CONCLUSION

Gata3, Eomes, Tfap2c, Ets2 and Cdx2 overexpression in ESC resulted in stable iTSC fate independent of culture conditions. For four factors or Cdx2 alone, TX medium is required for complete TSC conversion.

TNFα-induced Up-regulation of Ascl2 Affects the Differentiation and Proliferation of Neural Stem Cells

The molecular mediators underlying the effects of inflammation on neural stem cells (NSCs) are not fully characterized. In this study, we identified Ascl2 as a downstream basic helix-loop-helix (bHLH) transcription factor in NSCs following exposure to TNFα. Under normal conditions, Ascl2 expression is inhibited at post-transcriptional levels by miR-26a, which targets the 3’ untranslated region (UTR) of Ascl2. Upon exposure to TNFα, miR-26a expression is reduced, which leads to up-regulation of Ascl2. Overexpression of Ascl2 promotes neuronal differentiation, reduces proliferation, and increases the level of cleaved CASPASE 3 in NSCs, as observed in the in vitro and in ovo experiments. Ascl2 may serve in NSCs as a standby factor that readily responds to TNFα, which is often induced in inflammatory situations. In a chronic inflammatory condition with consistent up-regulation of TNFα, overexpression of Ascl2 may inhibit neurogenesis as a net result.

Super-enhancer-guided mapping of regulatory networks controlling mouse trophoblast stem cells

Trophectoderm (TE) lineage development is pivotal for proper implantation, placentation, and healthy pregnancy. However, only a few TE-specific transcription factors (TFs) have been systematically characterized, hindering our understanding of the process. To elucidate regulatory mechanisms underlying TE development, here we map super-enhancers (SEs) in trophoblast stem cells (TSCs) as a model. We find both prominent TE-specific master TFs (Cdx2, Gata3, and Tead4), and >150 TFs that had not been previously implicated in TE lineage, that are SE-associated. Mapping targets of 27 SE-predicted TFs reveals a highly intertwined transcriptional regulatory circuitry. Intriguingly, SE-predicted TFs show 4 distinct expression patterns with dynamic alterations of their targets during TSC differentiation. Furthermore, depletion of a subset of TFs results in dysregulation of the markers for specialized cell types in placenta, suggesting a role during TE differentiation. Collectively, we characterize an expanded TE-specific regulatory network, providing a framework for understanding TE lineage development and placentation.

Trophectoderm lineage development is essential for implantation, placentation, and healthy pregnancy. Here the authors map super-enhancers (SEs) in trophoblast stem cells and find both TE-specific master regulators and 150 previous uncharacterised transcription factors that are SE-associated, providing insight into trophectoderm-specific regulatory networks.

Embryonic Cul4b is important for epiblast growth and location of primitive streak layer cells

Cul4b-null (Cul4bΔ/Y) mice undergo growth arrest and degeneration during the early embryonic stages and die at E9.5. The pathogenic causes of this lethality remain incompletely characterized. However, it has been hypothesized that the loss of Cul4b function in extraembryonic tissues plays a key role. In this study, we investigated possible causes of death for Cul4b-null embryos, particularly in regard to the role of embryonic Cul4b. First, we show that the loss of embryonic Cul4b affects the growth of the inner cell mass in vitro and delays epiblast development during the gastrulation period at E6.5~E7.5 in vivo, as highlighted by the absence of the epiblastic transcription factor Brachyury from E6.5~E7.5. Additionally, at E7.5, strong and laterally expanded expression of Eomes and Fgf8 signaling was detected. Sectioning of these embryos showed disorganized primitive streak layer cells. Second, we observed that Mash2-expressing cells were present in the extraembryonic tissues of Cul4b-deficient embryos at E6.5 but were absent at E7.5. In addition, the loss of Cul4b resulted in decreased expression of cyclin proteins, which are required for the cell cycle transition from G1 to S. Taken together, these observations suggest that the embryonic expression of Cul4b is important for epiblast growth during E6.5~E7.5, and the loss of Cul4b results in either delayed growth of the epiblast or defective localization of primitive streak layer cells. As a result, the signaling activity mediated by the epiblast for subsequent ectoplacental cone development is affected, with the potential to induce growth retardation and lethality in Cul4bΔ/Y embryos.

Specific Labeling of Stem Cell Activity in Human Colorectal Organoids Using an ASCL2-Responsive Minigene

Organoid technology provides the possibility of culturing patient-derived colon tissue and colorectal cancers (CRCs) while maintaining all functional and phenotypic characteristics. Labeling stem cells, especially in normal and benign tumor organoids of human colon, is challenging and therefore limits maximal exploitation of organoid libraries for human stem cell research. Here, we developed STAR (stem cell Ascl2 reporter), a minimal enhancer/promoter element that reports transcriptional activity of ASCL2, a master regulator of LGR5⁺ intestinal stem cells. Using lentiviral infection, STAR drives specific expression in stem cells of normal organoids and in multiple engineered and patient-derived CRC organoids of different genetic makeup. STAR reveals that differentiation hierarchies and the potential for cell fate plasticity are present at all stages of human CRC development. Organoid technology, in combination with the user-friendly nature of STAR, will facilitate basic research into human adult stem cell biology.

Physiological profile of undifferentiated bovine blastocyst-derived trophoblasts

Trophectoderm of blastocysts mediate early events in fetal-maternal communication, enabling implantation and establishment of a functional placenta. Inadequate or impaired developmental events linked to trophoblasts directly impact early embryo survival and successful implantation during a crucial period that corresponds with high incidence of pregnancy losses in dairy cows. As yet, the molecular basis of bovine trophectoderm development and signaling towards initiation of implantation remains poorly understood. In this study, we developed methods for culturing undifferentiated bovine blastocyst-derived trophoblasts and used both transcriptomics and proteomics in early colonies to categorize and elucidate their functional characteristics. A total of 9270 transcripts and 1418 proteins were identified and analyzed based on absolute abundance. We profiled an extensive list of growth factors, cytokines and other relevant factors that can effectively influence paracrine communication in the uterine microenvironment. Functional categorization and analysis revealed novel information on structural organization, extracellular matrix composition, cell junction and adhesion components, transcription networks, and metabolic preferences. Our data showcase the fundamental physiology of bovine trophectoderm and indicate hallmarks of the self-renewing undifferentiated state akin to trophoblast stem cells described in other species. Functional features uncovered are essential for understanding early events in bovine pregnancy towards initiation of implantation.

Summary: Fundamental physiology of the bovine trophectoderm and hallmarks of the self-renewing undifferentiated ‘trophoblast stem cells’ are interpreted through systematic analysis of the cellular proteome and transcriptome.

Gestational exposure to acrylamide inhibits mouse placental development in vivo

Acrylamide, a carcinogen and neurotoxic substance, recently has been discovered in various heat-treated carbohydrate-rich foods. The aim of this study was to investigate the effects of acrylamide exposure on placental development. Pregnant mice received acrylamide by gavage at dosages of 0, 10, and 50 mg/kg/day from gestational days (GD) 3 until GD 8 or GD 13. The results showed that acrylamide feeding significantly decreased the numbers of viable embryos and increased the numbers of resorbed embryos on GD 13. Acrylamide exposure reduced the absolute and relative weight of placentas and embryos, and inhibited the development of ectoplacental cone (EPC) and placenta, as shown by the atrophy of EPC and reduced placental area. Acrylamide markedly reduced the numbers of labyrinth vessels. Expression levels of most placental key genes such as Esx1, Hand1, and Hand2 mRNA dramatically decreased in acrylamide-treated placentas. Furthermore, acrylamide treatment inhibited proliferation and induced apoptosis of placentas, as shown by decreased Ki67-positive cells and Bcl-2 protein, and increased the expression of Bax, cleaved-caspase-3, and cleaved-caspase-8 proteins. In conclusion, our results indicated that gestational exposure to acrylamide inhibits placental development through dysregulation of placental key gene expression and labyrinth vessels, suppression of proliferation, and apoptosis induction in mice.

Optimal-Transport Analysis of Single-Cell Gene Expression Identifies Developmental Trajectories in Reprogramming

Understanding the molecular programs that guide differentiation during development is a major challenge. Here, we introduce Waddington-OT, an approach for studying developmental time courses to infer ancestor-descendant fates and model the regulatory programs that underlie them. We apply the method to reconstruct the landscape of reprogramming from 315,000 single-cell RNA sequencing (scRNA-seq) profiles, collected at half-day intervals across 18 days. The results reveal a wider range of developmental programs than previously characterized. Cells gradually adopt either a terminal stromal state or a mesenchymal-to-epithelial transition state. The latter gives rise to populations related to pluripotent, extra-embryonic, and neural cells, with each harboring multiple finer subpopulations. The analysis predicts transcription factors and paracrine signals that affect fates and experiments validate that the TF Obox6 and the cytokine GDF9 enhance reprogramming efficiency. Our approach sheds light on the process and outcome of reprogramming and provides a framework applicable to diverse temporal processes in biology.

Murine transcription factor Math6 is a regulator of placenta development

The murine basic helix-loop-helix transcription (bHLH) factor mouse atonal homolog 6 (Math6) is expressed in numerous organs and supposed to be involved in several developmental processes. However, so far neither all aspects nor the molecular mechanisms of Math6 function have been explored exhaustively. To analyze the in vivo function of Math6 in detail, we generated a constitutive knockout (KO) mouse (Math6^−/−) and performed an initial histological and molecular biological investigation of its main phenotype. Pregnant Math6^−/− females suffer from a disturbed early placental development leading to the death of the majority of embryos independent of the embryonic Math6 genotype. A few placentas and fetuses survive the severe uterine hemorrhagic events at late mid-gestation (E13.5) and subsequently develop regularly. However, these fetuses could not be born due to obstructions within the gravid uterus, which hinder the birth process. Characterization of the endogenous spatiotemporal Math6 expression during placenta development reveals that Math6 is essential for an ordered decidualization and an important regulator of the maternal-fetal endocrine crosstalk regulating endometrial trophoblast invasion and differentiation. The strongly disturbed vascularization observed in the maternal placenta appears as an additional consequence of the altered endocrine status and as the main cause for the general hemorrhagic crisis.

Transcription factor ASCL2 is required for development of the glycogen trophoblast cell lineage

The basic helix-loop-helix (bHLH) transcription factor ASCL2 plays essential roles in diploid multipotent trophoblast progenitors, intestinal stem cells, follicular T-helper cells, as well as during epidermal development and myogenesis. During early development, Ascl2 expression is regulated by genomic imprinting and only the maternally inherited allele is transcriptionally active in trophoblast. The paternal allele-specific silencing of Ascl2 requires expression of the long non-coding RNA Kcnq1ot1 in cis and the deposition of repressive histone marks. Here we show that Del^7AI, a 280-kb deletion allele neighboring Ascl2, interferes with this process in cis and leads to a partial loss of silencing at Ascl2. Genetic rescue experiments show that the low level of Ascl2 expression from the paternal Del^7AI allele can rescue the embryonic lethality associated with maternally inherited Ascl2 mutations, in a level-dependent manner. Despite their ability to support development to term, the rescued placentae have a pronounced phenotype characterized by severe hypoplasia of the junctional zone, expansion of the parietal trophoblast giant cell layer, and complete absence of invasive glycogen trophoblast cells. Transcriptome analysis of ectoplacental cones at E7.5 and differentiation assays of Ascl2 mutant trophoblast stem cells show that ASCL2 is required for the emergence or early maintenance of glycogen trophoblast cells during development. Our work identifies a new cis-acting mutation interfering with Kcnq1ot1 silencing function and establishes a novel critical developmental role for the transcription factor ASCL2.

By controlling precise networks of target genes, transcription factors play important roles in cell fate determination during development. The Ascl2 gene codes for a transcription factor essential for the maintenance of progenitor cell populations able to differentiate into specialized cell types in the intestine and in the extra-embryonic trophoblast lineage. The trophoblast is an essential component of the placenta, an organ required for development of the embryo in placental mammals. Ascl2 belongs to a group of unusual genes, called imprinted genes, which are expressed from only a single parental copy. Ascl2 is only expressed from the maternally inherited copy in the trophoblast, the paternal copy being kept silent. Here, we describe an engineered deletion neighboring Ascl2 that interferes with the complete silencing of the paternal copy of the gene. We show that the low amount of ASCL2 produced from this deletion can rescue the embryonic lethality associated with non-functional maternal copies of Ascl2. Although the rescued embryos can often survive to term, their placenta is highly disorganized and lacks members of a specific cell lineage, the trophoblast glycogen cells. By analyzing the transcriptional profile of mutant trophoblast progenitors in vivo and of differentiated trophoblast stem cells, we show that ASCL2 plays a very early role in the formation of this cell lineage.

NOSTRIN: A novel modulator of trophoblast giant cell differentiation

Differentiation-dependent expression of NOSTRIN in murine trophoblast cells prompted investigation on NOSTRIN's function in trophoblast differentiation. We show here that NOSTRIN levels increased in both mouse and rat placenta during gestation. NOSTRIN expression was not co-related to expression of eNOS precluding its eNOS mediated function. NOSTRIN transcripts were identified in trophoblast cells of the placenta, predominantly in trophoblast giant cells (TGC). Precocious over-expression of NOSTRIN during differentiation of trophoblast stem cells led to up-regulation of genetic markers associated with invasion (Prl4a1, Prl2a1) and TGC formation (Prl2c2, Prl3d1, Prl3b1). The functional consequence of NOSTRIN over-expression was increased TGC formation and trophoblast cell invasion. Furthermore, number of polyploid TGCs that arise by endoreduplication, were higher in presence of NOSTRIN. Early induction of NOSTRIN was associated with substantial decrease in G/F actin ratio and augmentation of N-WASP-Dynamin-NOSTRIN ternary complex formation that might be partially responsible for nucleation of actin filaments. NOSTRIN also formed a complex with Cdk1 and increased phosphorylation of T14 and Y15 residues that inhibits cytokinesis. Interestingly, SH3 domain deleted NOSTRIN was ineffective in eliciting NOSTRIN's function in differentiating trophoblast cells. These findings demonstrate that NOSTRIN potentiates trophoblast differentiation towards TGC trajectory that is critical for hemochorial placentation.

Effects of excess thromboxane A2 on placental development and nutrient transporters in a Mus musculus model of fetal growth restriction

Hypertensive disease of pregnancy (HDP) with placental insufficiency is the most common cause of fetal growth restriction (FGR) in the developed world. Despite the known negative consequences of HDP both to the mother and fetus, little is known about the longitudinal placental changes that occur as HDP progresses in pregnancy. This is because longitudinal sampling of human placentae during each gestation is impossible. Therefore, using a mouse model of thromboxane A2-analog infusion to mimic human HDP in the last trimester, we calculated placental efficiencies based on fetal and placental weights; quantified spongiotrophoblast and labyrinth thicknesses and vascular density within these layers; examined whether hypoxia signaling pathway involving vascular endothelial growth factor A (VEGFA) and its receptors (VEGFR1, VEGFR2) and matrix metalloproteinases (MMPs) contributed to vascular change; and examined nutrient transporter abundance including glucose transporters 1 and 3 (GLUT1, GLUT3), neutral amino acid transporters 1, 2, and 4 (SNAT1, SNAT2, and SNAT4), fatty acid transporters 2 and 4 (FATP2, FATP4), and fatty acid translocase (CD36) from embryonic day 15.5 to 19 in a 20-day C57Bl/6J mouse gestation. We conclude that early-to-mid gestation hypertensive placentae show compensatory mechanisms to preserve fetal growth by increasing placental efficiencies and maintaining abundance of important nutrient transporters. As placental vascular network diminishes over late hypertension, placental efficiency diminishes and fetal growth fails. Neither hypoxia signaling pathway nor MMPs mediated the vascular diminution in this model. Hypertensive placentae surprisingly exhibit a sex-differential expression of nutrient transporters in late gestation despite showing fetal growth failure in both sexes.

Nucleosomes of polyploid trophoblast giant cells mostly consist of histone variants and form a loose chromatin structure

Trophoblast giant cells (TGCs) are one of the cell types that form the placenta and play multiple essential roles in maintaining pregnancy in rodents. TGCs have large, polyploid nuclei resulting from endoreduplication. While previous studies have shown distinct gene expression profiles of TGCs, their chromatin structure remains largely unknown. An appropriate combination of canonical and non-canonical histones, also known as histone variants, allows each cell to exert its cell type-specific functions. Here, we aimed to reveal the dynamics of histone usage and chromatin structure during the differentiation of trophoblast stem cells (TSCs) into TGCs. Although the expression of most genes encoding canonical histones was downregulated, the expression of a few genes encoding histone variants such as H2AX, H2AZ, and H3.3 was maintained at a relatively high level in TGCs. Both the micrococcal nuclease digestion assay and nucleosome stability assay using a microfluidic device indicated that chromatin became increasingly loose as TSCs differentiated. Combinatorial experiments involving H3.3-knockdown and -overexpression demonstrated that variant H3.3 resulted in the formation of loose nucleosomes in TGCs. In conclusion, our study revealed that TGCs possessed loose nucleosomes owing to alterations in their histone composition during differentiation.

Apposition to endometrial epithelial cells activates mouse blastocysts for implantation

STUDY QUESTION

How do interactions between blastocyst-stage embryos and endometrial epithelial cells regulate the early stages of implantation in an in vitro model?

SUMMARY ANSWER

Mouse blastocyst apposition with human endometrial epithelial cells initiates trophectoderm differentiation to trophoblast, which goes on to breach the endometrial epithelium.

WHAT IS KNOWN ALREADY

In vitro models using mouse blastocysts and human endometrial cell lines have proven invaluable in the molecular characterisation of embryo attachment to endometrial epithelium at the onset of implantation. Genes involved in embryonic breaching of the endometrial epithelium have not been investigated in such in vitro models.

STUDY DESIGN, SIZE, DURATION

This study used an established in vitro model of implantation to examine cellular and molecular interactions during blastocyst attachment to endometrial epithelial cells.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Mouse blastocysts developed from embryonic day (E) 1.5 in vitro were hatched and co-cultured with confluent human endometrial adenocarcinoma-derived Ishikawa cells in serum-free medium. A scale of attachment stability based on blastocyst oscillation upon agitation was devised. Blastocysts were monitored for 48 h to establish the kinetics of implantation, and optical sectioning using fluorescence microscopy revealed attachment and invasion interfaces. Quantitative PCR was used to determine blastocyst gene expression. Data from a total of 680 mouse blastocysts are reported, with 3-6 experimental replicates. T-test and ANOVA analyses established statistical significance at P < 0.05, P < 0.01 and P < 0.001.

MAIN RESULTS AND THE ROLE OF CHANCE

Hatched E4.5 mouse blastocysts exhibited weak attachment to confluent Ishikawa cells over the first 24 h of co-culture, with intermediate and stable attachment occurring from 28 h (E5.5 + 4 h) in a hormone-independent manner. Attached embryos fixed after 48 h (E6.5) frequently exhibited outgrowths, characterised morphologically and with antibody markers as trophoblast giant cells (TGCs), which had breached the Ishikawa cell layer. Beginning co-culture at E5.5 also resulted in intermediate and stable attachment from E5.5 + 4 h; however, these embryos did not go on to breach the Ishikawa cell layer, even when co-culture was extended to E7.5 (P < 0.01). Blastocysts cultured from E4.5 in permeable transwell inserts above Ishikawa cells before transfer to direct co-culture at E5.5 went on to attach but failed to breach the Ishikawa cell layer by E6.5 (P < 0.01). Gene expression analysis at E5.5 demonstrated that direct co-culture with Ishikawa cells from E4.5 resulted in downregulation of trophectoderm transcription factors Cdx2 (P < 0.05) and Gata3 (P < 0.05) and upregulation of the TGC transcription factor Hand1 (P < 0.05). Co-culture with non-endometrial human fibroblasts did not alter the expression of these genes.

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

The in vitro model used here combines human carcinoma-derived endometrial cells with mouse embryos, in which the cellular interactions observed may not fully recapitulate those in vivo. The data gleaned from such models can be regarded as hypothesis-generating, and research is now needed to develop more sophisticated models of human implantation combining multiple primary endometrial cell types with surrogate and real human embryos.

WIDER IMPLICATIONS OF THE FINDINGS

This study implicates blastocyst apposition to endometrial epithelial cells as a critical step in trophoblast differentiation required for implantation. Understanding this maternal regulation of the embryonic developmental programme may lead to novel treatments for infertility.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was supported by funds from the charities Wellbeing of Women (RG1442) and Diabetes UK (15/0005207), and studentship support for SCB from the Anatomical Society. No conflict of interest is declared.

Human Long Noncoding RNA Regulation of Stem Cell Potency and Differentiation

Because of their capability of differentiation into lineage-specific cells, stem cells are an attractive therapeutic modality in regenerative medicine. To develop an effective stem cell-based therapeutic strategy with predictable results, deeper understanding of the underlying molecular mechanisms of stem cell differentiation and/or pluripotency maintenance is required. Thus, reviewing the key factors involved in the transcriptional and epigenetic regulation of stem cell differentiation and maintenance is important. Accumulating data indicate that long noncoding RNAs (lncRNAs) mediate numerous biological processes, including stem cell differentiation and maintenance. Here, we review recent findings on the human lncRNA regulation of stem cell potency and differentiation. Although the clinical implication of these lncRNAs is only beginning to be elucidated, it is anticipated that lncRNAs will become important therapeutic targets in the near future.

Transplacental exposure to environmental carcinogens: Association with childhood cancer risks and the role of modulating factors

Biological responses to carcinogens from environmental exposure during adulthood are modulated over years or decades. Conversely, during transplacental exposure, the effects on the human foetus change within weeks, intertwining with developmental mechanisms: even short periods of transplacental exposure may be imprinted in the organism for a lifetime. The pathways leading to childhood and juvenile cancers, such as leukaemias, neuroblastoma/brain tumours, hepatoblastoma, and Willm's tumour involve prenatally-induced genomic, epigenomic and/or non-genomic effects caused by xenobiotics. Pregnant women most often live in complex environmental settings that cause transplacental exposure of the foetus to xenobiotic mixtures. Mother-child biomonitoring should integrate the analysis of chemicals/radiation present in the living and workplace environment with relevant risk modulators related to life style. The interdisciplinary approach for transplacental cancer risk assessment in high-pressure areas should be based on an integrated model for mother-child exposure estimation via profiling the exposure level by water quality analysis, usage of emission grids, and land use maps.

ARID3A is required for mammalian placenta development

Previous studies in the mouse indicated that ARID3A plays a critical role in the first cell fate decision required for generation of trophectoderm (TE). Here, we demonstrate that ARID3A is widely expressed during mouse and human placentation and essential for early embryonic viability. ARID3A localizes to trophoblast giant cells and other trophoblast-derived cell subtypes in the junctional and labyrinth zones of the placenta. Conventional Arid3a knockout embryos suffer restricted intrauterine growth with severe defects in placental structural organization. Arid3a null placentas show aberrant expression of subtype-specific markers as well as significant alteration in cytokines, chemokines and inflammatory response-related genes, including previously established markers of human placentation disorders. BMP4-mediated induction of trophoblast stem (TS)-like cells from human induced pluripotent stem cells results in ARID3A up-regulation and cytoplasmic to nuclear translocation. Overexpression of ARID3A in BMP4-mediated TS-like cells up-regulates TE markers, whereas pluripotency markers are down-regulated. Our results reveal an essential, conserved function for ARID3A in mammalian placental development through regulation of both intrinsic and extrinsic developmental programs.

Haploinsufficiency of Hand1 improves mice survival after acute myocardial infarction through preventing cardiac rupture

Previous studies have demonstrated a significantly lower level of Hand1 in ischemic cardiomyopathy than in normal heart tissue. The role of decreased Hand1 in myocardial infarction remains unclear. This study was designed to investigate the effects of haploinsufficiency of Hand1 on mouse heart after myocardial infarction. 8-10 weeks old male heterozygous Hand1-deficient (Hand1(+/-)) mice and wild-type littermates (control) were subjected to sham operation or ligation of the left anterior descending coronary artery to induce acute myocardial infarction (AMI). Hand1(+/-) mice have low incidence of left ventricular free wall rupture in the first week after operation than control mice. Then we found lower MMP9 activity and less cardiomyocytes apoptosis in Hand1(+/-) than in control mice. All of these contribute to the protection role of haploinsufficiency of Hand1 after AMI.