Loss of Cited2 affects trophoblast formation and vascularization of the mouse placenta

Identification and Functional Verification of CITED2 Gene Promoter Region in Patients with Patent Ductus Arteriosus

Patent ductus arteriosus (PDA) is a common congenital heart disease. CITED2 plays an important role in the development of the heart, and genetic variants in its coding region are significantly associated with cardiac malformations. However, the role of variants in the promoter region of CITED2 in the development of PDA remains unclear. We extracted the peripheral blood of 646 subjects (including 353 PDA patients and 293 unrelated healthy controls) for sequencing. We identified 13 promoter variants of the CITED2 gene (including 2 novel heterozygous variants). Of the 13 variants, 10 were found only in PDA patients. In mouse cardiomyocytes (HL-1) and rat cardiac myocytes (RCM), the transcriptional activity of the CITED2 gene promoter was significantly changed by the variants (p < 0.05). The results of the experiments of electrophoretic mobility indicated that these variants may affect the transcription of the CITED2 gene by influencing the binding ability of transcription factors. These results, combined with the JASPAR database analysis, showed that the destruction/production of transcription factor binding sites due to the variants in the promoter region of the CITED2 gene may directly or indirectly affect the binding ability of transcription factors. Our results suggest for the first time that variants at the CITED2 promoter region may cause low expression of CITED2 protein related to the formation of PDA.

Role of FBXL5 in redox homeostasis and spindle assembly during oocyte maturation in mice

As an E3 ubiquitin ligase, F-box and leucine-rich repeat protein 5 (FBXL5) participates in diverse biologic processes. However, the role of Fbxl5 in mouse oocyte meiotic maturation has not yet been fully elucidated. The present study revealed that mouse oocytes depleted of Fbxl5 were unable to complete meiosis, as Fbxl5 silencing led to oocyte meiotic failure with reduced rates of GVBD and polar body extrusion. In addition, Fbxl5 depletion induced aberrant mitochondrial dynamics as we noted the overproduction of reactive oxygen species (ROS) and the accumulation of phosphorylated γH2AX with Fbxl5 knockdown. We also found that Fbxl5-KD led to the abnormal accumulation of CITED2 proteins in mouse oocytes. Our in vitro ubiquitination assay showed that FBXL5 interacted with CITED2 and that it mediated the degradation of CITED2 protein through the ubiquitination-proteasome pathway. Collectively, our data revealed critical functions of FBXL5 in redox hemostasis and spindle assembly during mouse oocyte maturation.

Core conserved transcriptional regulatory networks define the invasive trophoblast cell lineage

The invasive trophoblast cell lineages in rat and human share crucial responsibilities in establishing the uterine-placental interface of the hemochorial placenta. These observations have led to the rat becoming an especially useful animal model for studying hemochorial placentation. However, our understanding of similarities or differences between regulatory mechanisms governing rat and human invasive trophoblast cell populations is limited. In this study, we generated single-nucleus ATAC-seq data from gestation day 15.5 and 19.5 rat uterine-placental interface tissues, and integrated the data with single-cell RNA-seq data generated at the same stages. We determined the chromatin accessibility profiles of invasive trophoblast, natural killer, macrophage, endothelial and smooth muscle cells, and compared invasive trophoblast chromatin accessibility with extravillous trophoblast cell accessibility. In comparing chromatin accessibility profiles between species, we found similarities in patterns of gene regulation and groups of motifs enriched in accessible regions. Finally, we identified a conserved gene regulatory network in invasive trophoblast cells. Our data, findings and analysis will facilitate future studies investigating regulatory mechanisms essential for the invasive trophoblast cell lineage.

CORE CONSERVED TRANSCRIPTIONAL REGULATORY NETWORKS DEFINE THE INVASIVE TROPHOBLAST CELL LINEAGE

The invasive trophoblast cell lineage in rat and human share crucial responsibilities in establishing the uterine-placental interface of the hemochorial placenta. These observations have led to the rat becoming an especially useful animal model to study hemochorial placentation. However, our understanding of similarities or differences between regulatory mechanisms governing rat and human invasive trophoblast cell populations is limited. In this study, we generated single-nucleus (sn) ATAC-seq data from gestation day (gd) 15.5 and 19.5 rat uterine-placental interface tissues and integrated the data with single-cell RNA-seq data generated at the same stages. We determined the chromatin accessibility profiles of invasive trophoblast, natural killer, macrophage, endothelial, and smooth muscle cells, and compared invasive trophoblast chromatin accessibility to extravillous trophoblast (EVT) cell accessibility. In comparing chromatin accessibility profiles between species, we found similarities in patterns of gene regulation and groups of motifs enriched in accessible regions. Finally, we identified a conserved gene regulatory network in invasive trophoblast cells. Our data, findings and analysis will facilitate future studies investigating regulatory mechanisms essential for the invasive trophoblast cell lineage.

Placental adaptations supporting fetal growth during normal and adverse gestational environments

NEW FINDINGS

What is the topic of this review? How the placenta, which transports nutrients and oxygen to the fetus, may alter its support of fetal growth developmentally and with adverse gestational conditions. What advances does it highlight? Placental formation and function alter with the needs of the fetus for substrates for growth during normal gestation and when there is enhanced competition for substrates in species with multiple gestations or adverse gestational environments, and this is mediated by imprinted genes, signalling pathways, mitochondria and fetal sexomes.

ABSTRACT

The placenta is vital for mammalian development and a key determinant of life-long health. It is the interface between the mother and fetus and is responsible for transporting the nutrients and oxygen a fetus needs to develop and grow. Alterations in placental formation and function, therefore, have consequences for fetal growth and birthweight, which in turn determine perinatal survival and risk of non-communicable diseases for the offspring in later postnatal life. However, the placenta is not a static organ. As this review summarizes, research from multiple species has demonstrated that placental formation and function alter developmentally to the needs of the fetus for substrates for growth during normal gestation, as well as when there is greater competition for substrates in polytocous species and monotocous species with multiple gestations. The placenta also adapts in response to the gestational environment, integrating information about the ability of the mother to provide nutrients and oxygen with the needs of the fetus in that prevailing environment. In particular, placental structure (e.g. vascularity, surface area, blood flow, diffusion distance) and transport capacity (e.g. nutrient transporter levels and activity) respond to suboptimal gestational environments, namely malnutrition, obesity, hypoxia and maternal ageing. Mechanisms mediating developmentally and environmentally induced homeostatic responses of the placenta that help support normal fetal growth include imprinted genes, signalling pathways, subcellular constituents and fetal sexomes. Identification of these placental strategies may inform the development of therapies for complicated human pregnancies and advance understanding of the pathways underlying poor fetal outcomes and their consequences for health and disease risk.

Development and function of the fetal adrenal

The adrenal cortex undergoes multiple structural and functional rearrangements to satisfy the systemic needs for steroids during fetal life, postnatal development, and adulthood. A fully functional adrenal cortex relies on the proper subdivision in regions or 'zones' with distinct but interconnected functions, which evolve from the early embryonic stages to adulthood, and rely on a fine-tuned gene network. In particular, the steroidogenic activity of the fetal adrenal is instrumental in maintaining normal fetal development and growth. Here, we review and discuss the most recent advances in our understanding of embryonic and fetal adrenal development, including the known causes for adrenal dys-/agenesis, and the steroidogenic pathways that link the fetal adrenal with the hormone system of the mother through the fetal-placental unit. Finally, we discuss what we think are the major open questions in the field, including, among others, the impact of osteocalcin, thyroid hormone, and other hormone systems on adrenal development and function, and the reliability of rodents as models of adrenal pathophysiology.

HIF1 inhibitor acriflavine rescues early-onset preeclampsia phenotype in mice lacking placental prolyl hydroxylase domain protein 2

Preeclampsia is a serious pregnancy disorder that lacks effective treatments other than delivery. Improper sensing of oxygen changes during placentation by prolyl hydroxylases (PHDs), specifically PHD2, causes placental hypoxia-inducible factor-1 (HIF1) buildup and abnormal downstream signaling in early-onset preeclampsia, yet therapeutic targeting of HIF1 has never been attempted. Here we generated a conditional (placenta-specific) knockout of Phd2 in mice (Phd2-/- cKO) to reproduce HIF1 excess and to assess anti-HIF therapy. Conditional deletion of Phd2 in the junctional zone during pregnancy increased placental HIF1 content, resulting in abnormal placentation, impaired remodeling of the uterine spiral arteries, and fetal growth restriction. Pregnant dams developed new-onset hypertension at midgestation (E9.5) in addition to proteinuria and renal and cardiac pathology, hallmarks of severe preeclampsia in humans. Daily injection of acriflavine, a small molecule inhibitor of HIF1, to pregnant Phd2-/- cKO mice from E7.5 (prior to hypertension) or E10.5 (after hypertension had been established) to E14.5 corrected placental dysmorphologies and improved fetal growth. Moreover, it reduced maternal blood pressure and reverted renal and myocardial pathology. Thus, therapeutic targeting of the HIF pathway may improve placental development and function, as well as maternal and fetal health, in preeclampsia.

Genetic Variants of CITED2 Gene Promoter in Human Atrial Septal Defects: Case-Control Study and Cellular Functional Verification

Atrial septal defect (ASD) is one of the most common forms of congenital heart disease (CHD). Genetic variants in the coding region of the CITED2 gene are known to be significantly correlated with CHD, but the role of variants in the promoter region of CITED2 is unknown. We investigated variants in the promoter of the CITED2 gene in 625 subjects (332 ASD and 293 healthy controls) through Sanger sequencing. Four variants in the CITED2 gene promoter were found only in eight ASD patients with zero occurrence in the control subjects (one case of g.4078A>C(rs1165649373), one case of g.4240C>A(rs1235857801), four cases of g.4935C>T(rs111470468), two cases of g.5027C>T(rs112831934)). Cellular functional analysis showed that these four variants significantly changed the transcriptional activity of the CITED2 gene promoter in HEK-293 and HL-1 cells. Electrophoretic mobility change assay results and JASPAR database analysis demonstrated that these variants created or destroyed a series of possible transcription factor binding sites, resulting in changes in the expression of CITED2 protein. We conclude that the variants of CITED2 promoter in ASD patients affect the transcriptional activity and are likely involved in the occurrence and development of ASD. These findings provide new perspectives on the pathogenesis and potential therapeutic insights of ASD.

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.

Mouse oocytes develop in cysts with the help of nurse cells

Mouse germline cysts, on average, develop into six oocytes supported by 24 nurse cells that transfer cytoplasm and organelles to generate a Balbiani body. We showed that between E14.5 and P5, cysts periodically activate some nurse cells to begin cytoplasmic transfer, which causes them to shrink and turnover within 2 days. Nurse cells die by a programmed cell death (PCD) pathway involving acidification, similar to Drosophila nurse cells, and only infrequently by apoptosis. Prior to initiating transfer, nurse cells co-cluster by scRNA-seq with their pro-oocyte sisters, but during their final 2 days, they cluster separately. The genes promoting oocyte development and nurse cell PCD are upregulated, whereas the genes that repress transfer, such as Tex14, and oocyte factors, such as Nobox and Lhx8, are under-expressed. The transferred nurse cell centrosomes build a cytocentrum that establishes a large microtubule aster in the primordial oocyte that organizes the Balbiani body, defining the earliest oocyte polarity.

Analysis of Placental Arteriovenous Formation Reveals New Insights Into Embryos With Congenital Heart Defects

The placental vasculature provides the developing embryo with a circulation to deliver nutrients and dispose of waste products. However, in the mouse, the vascular components of the chorio-allantoic placenta have been largely unexplored due to a lack of well-validated molecular markers. This is required to study how these blood vessels form in development and how they are impacted by embryonic or maternal defects. Here, we employed marker analysis to characterize the arterial/arteriole and venous/venule endothelial cells (ECs) during normal mouse placental development. We reveal that placental ECs are potentially unique compared with their embryonic counterparts. We assessed embryonic markers of arterial ECs, venous ECs, and their capillary counterparts-arteriole and venule ECs. Major findings were that the arterial tree exclusively expressed Dll4, and venous vascular tree could be distinguished from the arterial tree by Endomucin (EMCN) expression levels. The relationship between the placenta and developing heart is particularly interesting. These two organs form at the same stages of embryogenesis and are well known to affect each other's growth trajectories. However, although there are many mouse models of heart defects, these are not routinely assessed for placental defects. Using these new placental vascular markers, we reveal that mouse embryos from one model of heart defects, caused by maternal iron deficiency, also have defects in the formation of the placental arterial, but not the venous, vascular tree. Defects to the embryonic cardiovascular system can therefore have a significant impact on blood flow delivery and expansion of the placental arterial tree.

CITED2 coordinates key hematopoietic regulatory pathways to maintain the HSC pool in both steady-state hematopoiesis and transplantation

Hematopoietic stem cells (HSCs) reside at the apex of the hematopoietic differentiation hierarchy and sustain multilineage hematopoiesis. Here, we show that the transcriptional regulator CITED2 is essential for life-long HSC maintenance. While hematopoietic-specific Cited2 deletion has a minor impact on steady-state hematopoiesis, Cited2-deficient HSCs are severely depleted in young mice and fail to expand upon aging. Moreover, although they home normally to the bone marrow, they fail to reconstitute hematopoiesis upon transplantation. Mechanistically, CITED2 is required for expression of key HSC regulators, including GATA2, MCL-1, and PTEN. Hematopoietic-specific expression of anti-apoptotic MCL-1 partially rescues the Cited2-deficient HSC pool and restores their reconstitution potential. To interrogate the Cited2→Pten pathway in HSCs, we generated Cited2;Pten compound heterozygous mice, which had a decreased number of HSCs that failed to reconstitute the HSC compartment. In addition, CITED2 represses multiple pathways whose elevated activity causes HSC exhaustion. Thus, CITED2 promotes pathways necessary for HSC maintenance and suppresses those detrimental to HSC integrity.

Hypoxia Pathway Proteins and Their Impact on the Blood Vasculature

Every cell in the body requires oxygen for its functioning, in virtually every animal, and a tightly regulated system that balances oxygen supply and demand is therefore fundamental. The vascular network is one of the first systems to sense oxygen, and deprived oxygen (hypoxia) conditions automatically lead to a cascade of cellular signals that serve to circumvent the negative effects of hypoxia, such as angiogenesis associated with inflammation, tumor development, or vascular disorders. This vascular signaling is driven by central transcription factors, namely the hypoxia inducible factors (HIFs), which determine the expression of a growing number of genes in endothelial cells and pericytes. HIF functions are tightly regulated by oxygen sensors known as the HIF-prolyl hydroxylase domain proteins (PHDs), which are enzymes that hydroxylate HIFs for eventual proteasomal degradation. HIFs, as well as PHDs, represent attractive therapeutic targets under various pathological settings, including those involving vascular (dys)function. We focus on the characteristics and mechanisms by which vascular cells respond to hypoxia under a variety of conditions.

CITED2 inhibits STAT1-IRF1 signaling and atherogenesis

Macrophages are the principal component of the innate immune system. They play very crucial and multifaceted roles in the pathogenesis of inflammatory vascular diseases. There is an increasing recognition that transcriptionally dynamic macrophages are the key players in the pathogenesis of inflammatory vascular diseases. In this context, the accumulation and aberrant activation of macrophages in the subendothelial layers govern atherosclerotic plaque development. Macrophage-mediated inflammation is an explicitly robust biological response that involves broad alterations in inflammatory gene expression. Thus, cell-intrinsic negative regulatory mechanisms must exist which can restrain inflammatory response in a spatiotemporal manner. In this study, we identified CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxyl-terminal domain 2 (CITED2) as one such cell-intrinsic negative regulator of inflammation. Our in vivo studies show that myeloid-CITED2-deficient mice on the Apoe^-/- background have larger atherosclerotic lesions on both control and high-fat/high-cholesterol diets. Our integrated transcriptomics and gene set enrichment analyses studies show that CITED2 deficiency elevates STAT1 and interferon regulatory factor 1 (IRF1) regulated pro-inflammatory gene expression in macrophages. At the molecular level, our studies identify that CITED2 deficiency elevates IFNγ-induced STAT1 transcriptional activity and STAT1 enrichment on IRF1 promoter in macrophages. More importantly, siRNA-mediated knockdown of IRF1 completely reversed elevated pro-inflammatory target gene expression in CITED2-deficient macrophages. Collectively, our study findings demonstrate that CITED2 restrains the STAT1-IRF1 signaling axis in macrophages and limits the development of atherosclerotic plaques.

SUV39H2 controls trophoblast stem cell fate

BACKGROUND

The placenta is formed by the coordinated expansion and differentiation of trophoblast stem (TS) cells along a multi-lineage pathway. Dynamic regulation of histone 3 lysine 9 (H3K9) methylation is pivotal to cell differentiation for many cell lineages, but little is known about its involvement in trophoblast cell development.

METHODS

Expression of H3K9 methyltransferases was surveyed in rat TS cells maintained in the stem state and following differentiation. The role of suppressor of variegation 3-9 homolog 2 (SUV39H2) in the regulation of trophoblast cell lineage development was investigated using a loss-of-function approach in rat TS cells and ex vivo cultured rat blastocysts.

RESULTS

Among the twelve-known H3K9 methyltransferases, only SUV39H2 exhibited robust differential expression in stem versus differentiated TS cells. SUV39H2 transcript and protein expression were high in the stem state and declined as TS cells differentiated. Disruption of SUV39H2 expression in TS cells led to an arrest in TS cell proliferation and activation of trophoblast cell differentiation. SUV39H2 regulated H3K9 methylation status at loci exhibiting differentiation-dependent gene expression. Analyses of SUV39H2 on ex vivo rat blastocyst development supported its role in regulating TS cell expansion and differentiation. We further identified SUV39H2 as a downstream target of caudal type homeobox 2, a master regulator of trophoblast lineage development.

CONCLUSIONS

Our findings indicate that SUV39H2 contributes to the maintenance of TS cells and restrains trophoblast cell differentiation.

GENERAL SIGNIFICANCE

SUV39H2 serves as a contributor to the epigenetic regulation of hemochorial placental development.

Adrenal cortex development and related disorders leading to adrenal insufficiency

The adult human adrenal cortex produces steroid hormones that are crucial for life, supporting immune response, glucose homeostasis, salt balance and sexual maturation. It consists of three histologically distinct and functionally specialized zones. The fetal adrenal forms from mesodermal material and produces predominantly adrenal C₁₉ steroids from its fetal zone, which involutes after birth. Transition to the adult cortex occurs immediately after birth for the formation of the zona glomerulosa and fasciculata for aldosterone and cortisol production and continues through infancy until the zona reticularis for adrenal androgen production is formed with adrenarche. The development of this indispensable organ is complex and not fully understood. This article gives an overview of recent knowledge gained of adrenal biology from two perspectives: one, from basic science studying adrenal development, zonation and homeostasis; and two, from adrenal disorders identified in persons manifesting with various isolated or syndromic forms of primary adrenal insufficiency.

CITED2 limits pathogenic inflammatory gene programs in myeloid cells

Monocyte‐derived macrophages are the major innate immune cells that provide the first line of cellular defense against infections or injuries. These recruited macrophages at the site of inflammation are exposed to a broad range of cytokines that categorically incite a robust pro‐inflammatory response. However, macrophage pro‐inflammatory activation must be under exquisite control to avert unbridled inflammation. Thus, endogenous mechanisms must exist that rigorously preserve macrophage quiescence and yet, allow nimble pro‐inflammatory macrophage response with precise spatiotemporal control. Herein, we identify the CBP/p300‐interacting transactivator with glutamic acid/aspartic acid‐rich carboxyl‐terminal domain 2 (CITED2) as a critical intrinsic negative regulator of inflammation, which broadly attenuates pro‐inflammatory gene programs in macrophages. Our in vivo studies revealed that myeloid‐CITED2 deficiency significantly heightened macrophages and neutrophils recruitment to the site of inflammation. Our integrated transcriptomics and gene set enrichment analysis (GSEA) studies uncovered that CITED2 deficiency broadly enhances NFκB targets, IFNγ/IFNα responses, and inflammatory response gene expression in macrophages. Using complementary gain‐ and loss‐of‐function studies, we observed that CITED2 overexpression attenuate and CITED2 deficiency elevate LPS‐induced NFκB transcriptional activity and NFκB‐p65 recruitment to target gene promoter in macrophages. More importantly, blockade of NFκB signaling completely reversed elevated pro‐inflammatory gene expression in macrophages. Collectively, our findings show that CITED2 restrains NFκB activation and curtails broad pro‐inflammatory gene programs in myeloid cells.

Atypical protein kinase C iota (PKCλ/ι) ensures mammalian development by establishing the maternal-fetal exchange interface

In utero mammalian development relies on the establishment of the maternal-fetal exchange interface, which ensures transportation of nutrients and gases between the mother and the fetus. This exchange interface is established via development of multinucleated syncytiotrophoblast cells (SynTs) during placentation. In mice, SynTs develop via differentiation of the trophoblast stem cell-like progenitor cells (TSPCs) of the placenta primordium, and in humans, SynTs are developed via differentiation of villous cytotrophoblast (CTB) progenitors. Despite the critical need in pregnancy progression, conserved signaling mechanisms that ensure SynT development are poorly understood. Herein, we show that atypical protein kinase C iota (PKCλ/ι) plays an essential role in establishing the SynT differentiation program in trophoblast progenitors. Loss of PKCλ/ι in the mouse TSPCs abrogates SynT development, leading to embryonic death at approximately embryonic day 9.0 (E9.0). We also show that PKCλ/ι-mediated priming of trophoblast progenitors for SynT differentiation is a conserved event during human placentation. PKCλ/ι is selectively expressed in the first-trimester CTBs of a developing human placenta. Furthermore, loss of PKCλ/ι in CTB-derived human trophoblast stem cells (human TSCs) impairs their SynT differentiation potential both in vitro and after transplantation in immunocompromised mice. Our mechanistic analyses indicate that PKCλ/ι signaling maintains expression of GCM1, GATA2, and PPARγ, which are key transcription factors to instigate SynT differentiation programs in both mouse and human trophoblast progenitors. Our study uncovers a conserved molecular mechanism, in which PKCλ/ι signaling regulates establishment of the maternal-fetal exchange surface by promoting trophoblast progenitor-to-SynT transition during placentation.

CITED2 and the modulation of the hypoxic response in cancer

CITED2 (CBP/p300-interacting transactivator with Glu/Asp-rich C-terminal domain, 2) is a ubiquitously expressed protein exhibiting a high affinity for the CH1 domain of the transcriptional co-activators CBP/p300, for which it competes with hypoxia-inducible factors (HIFs). CITED2 is particularly efficient in the inhibition of HIF-1α-dependent transcription in different contexts, ranging from organ development and metabolic homeostasis to tissue regeneration and immunity, being also potentially involved in various other physiological processes. In addition, CITED2 plays an important role in inhibiting HIF in some diseases, including kidney and heart diseases and type 2-diabetes. In the particular case of cancer, CITED2 either functions by promoting or suppressing cancer development depending on the context and type of tumors. For instance, CITED2 overexpression promotes breast and prostate cancers, as well as acute myeloid leukemia, while its expression is downregulated to sustain colorectal cancer and hepatocellular carcinoma. In addition, the role of CITED2 in the maintenance of cancer stem cells reveals its potential as a target in non-small cell lung carcinoma and acute myeloid leukemia, for example. But besides the wide body of evidence linking both CITED2 and HIF signaling to carcinogenesis, little data is available regarding CITED2 role as a negative regulator of HIF-1α specifically in cancer. Therefore, comprehensive studies exploring further the interactions of these two important mediators in cancer-specific models are sorely needed and this can potentially lead to the development of novel targeted therapies.

DEAD Box Protein Family Member DDX28 Is a Negative Regulator of Hypoxia-Inducible Factor 2α- and Eukaryotic Initiation Factor 4E2-Directed Hypoxic Translation

Hypoxia is a deficiency in oxygen delivery to tissues and is connected to physiological and pathophysiological processes such as embryonic development and cancer. The master regulators of oxygen homeostasis in mammalian cells are the heterodimeric hypoxia-inducible transcription factors 1 and 2 (HIF-1 and HIF-2, respectively). The oxygen-labile HIF-2α subunit has been implicated not only in transcription but also as a regulator of eukaryotic initiation factor 4E2 (eIF4E2)-directed hypoxic translation. Here, we have identified the DEAD box protein family member DDX28 as an interactor and negative regulator of HIF-2α that suppresses HIF-2α's ability to activate eIF4E2-directed translation. Stable silencing of DDX28 via short hairpin RNA (shRNA) in hypoxic human U87MG glioblastoma cells caused an increase of eIF4E2 binding to the m⁷GTP cap structure and the translation of eIF4E2 target mRNAs (including the HIF-2α mRNA itself). DDX28 depletion elevated nuclear and cytoplasmic HIF-2α protein, but HIF-2α transcriptional activity did not increase, possibly due to its already high nuclear abundance in hypoxic control cells. Depletion of DDX28 conferred a proliferative advantage to hypoxic, but not normoxic, cells. DDX28 protein levels are reduced in several cancers, including gliomas, relative to levels in normal tissue. Therefore, we uncover a regulatory mechanism for this potential tumor suppressor in the repression of HIF-2α- and eIF4E2-mediated translation activation of oncogenic mRNAs.

Drug transport across the human placenta: review of placenta-on-a-chip and previous approaches

In the past few decades, the placenta became a very controversial topic that has had many researchers and pharmacists discussing the significance of the effects of pharmaceutical drug intake and how it is a possible leading cause towards birth defects. The creation of an in vitro microengineered model of the placenta can be used to replicate the interactions between the mother and fetus, specifically pharmaceutical drug intake reactions. As the field of nanotechnology significantly continues growing, nanotechnology will become more apparent in the study of medicine and other scientific disciplines, specifically microengineering applications. This review is based on past and current research that compares the feasibility and testing of the placenta-on-a-chip microengineered model to the previous and underdeveloped in vivo and ex vivo approaches. The testing of the practicality and effectiveness of the in vitro, in vivo and ex vivo models requires the experimentation of prominent pharmaceutical drugs that most mothers consume during pregnancy. In this case, these drugs need to be studied and tested more often. However, there are challenges associated with the in vitro, in vivo and ex vivo processes when developing a practical placental model, which are discussed in further detail.

Fetal and trophoblast PI3K p110α have distinct roles in regulating resource supply to the growing fetus in mice

Studies suggest that placental nutrient supply adapts according to fetal demands. However, signaling events underlying placental adaptations remain unknown. Here we demonstrate that phosphoinositide 3-kinase p110α in the fetus and the trophoblast interplay to regulate placental nutrient supply and fetal growth. Complete loss of fetal p110α caused embryonic death, whilst heterozygous loss resulted in fetal growth restriction and impaired placental formation and nutrient transport. Loss of trophoblast p110α resulted in viable fetuses, abnormal placental development and a failure of the placenta to transport sufficient nutrients to match fetal demands for growth. Using RNA-seq we identified genes downstream of p110α in the trophoblast that are important in adapting placental phenotype. Using CRISPR/Cas9 we showed loss of p110α differentially affects gene expression in trophoblast and embryonic stem cells. Our findings reveal important, but distinct roles for p110α in the different compartments of the conceptus, which control fetal resource acquisition and growth.

Deletion of Prl7d1 causes placental defects at mid-pregnancy in mice

Prolactin family 7, subfamily d, member 1 (Prl7d1), a member of the expanding prolactin family, is mainly expressed in the placental junctional zone (including trophoblast giant cells and spongiotrophoblast cells) with peak expression observed at 12 days postcoitum (dpc) in mice. Previous studies have shown that PRL7D1 is a key mediator of angiogenesis in vitro; however, its physiological roles in placental development in vivo have not been characterized. To address this issue, we deleted Prl7d1 in mice and demonstrated that its absence results in reduced litter size and fertility. Histologically, Prl7d1 mutants exhibited striking placental abnormalities at 12.5 dpc, including a reduction in the proportion of labyrinth layers and a significant increase in decidual natural killer cells, glycogen trophoblasts, and trophoblast giant cells in the junctional zone. Moreover, placentas from Prl7d1-null mice displayed a thickened decidual spiral artery. Notably, these negative effects were more pronounced in male fetuses. Further RNA-sequencing analysis showed that Prl7d1 deletion results in significant differences in the placental transcriptome profile between the two sexes of fetuses. Together, this study demonstrates that Prl7d1 possesses antiangiogenic properties in deciduas and inhibits the development of junctional zone, which potentially alters the functional capacity of the placenta to support optimal fetal growth. Moreover, of note, the role of Prl7d1 in the placenta is regulated in a fetal sex-specific manner.

USP22 controls multiple signaling pathways that are essential for vasculature formation in the mouse placenta

USP22, a component of the SAGA complex, is overexpressed in highly aggressive cancers, but the normal functions of this deubiquitinase are not well defined. We determined that loss of USP22 in mice results in embryonic lethality due to defects in extra-embryonic placental tissues and failure to establish proper vascular interactions with the maternal circulatory system. These phenotypes arise from abnormal gene expression patterns that reflect defective kinase signaling, including TGFβ and several receptor tyrosine kinase pathways. USP22 deletion in endothelial cells and pericytes that are induced from embryonic stem cells also hinders these signaling cascades, with detrimental effects on cell survival and differentiation as well as on the ability to form vessels. Our findings provide new insights into the functions of USP22 during development that may offer clues to its role in disease states.

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.

The Role of Abnormal Placentation in Congenital Heart Disease; Cause, Correlate, or Consequence?

Congenital heart disease (CHD) is the most common birth defect, affecting ~1% of all live births (van der Linde et al., 2011). Despite improvements in clinical care, it is the leading cause of infant mortality related to birth defects (Yang et al., 2006) and burdens survivors with significant morbidity (Gilboa et al., 2016). Furthermore, CHD accounts for the largest proportion (26.7%) of birth defect-associated hospitalization costs—up to $6.1 billion in 2013 (Arth et al., 2017). Yet after decades of research with a primary focus on genetic etiology, the underlying cause of these defects remains unknown in the majority of cases (Zaidi and Brueckner, 2017). Unexplained CHD may be secondary to undiscovered roles of noncoding genetic, epigenetic, and environmental factors, among others (Russell et al., 2018). Population studies have recently demonstrated that pregnancies complicated by CHD also carry a higher risk of developing pathologies associated with an abnormal placenta including growth disturbances (Puri et al., 2017), preeclampsia (Auger et al., 2015; Brodwall et al., 2016), preterm birth (Laas et al., 2012), and stillbirth (Jorgensen et al., 2014). Both the heart and placenta are vascular organs and develop concurrently; therefore, shared pathways almost certainly direct the development of both. The involvement of placental abnormalities in congenital heart disease, whether causal, commensurate or reactive, is under investigated and given the common developmental window and shared developmental pathways of the heart and placenta and concurrent vasculature development, we propose that further investigation combining clinical data, in vitro, in vivo, and computer modeling is fundamental to our understanding and the potential to develop therapeutics.

Near to One's Heart: The Intimate Relationship Between the Placenta and Fetal Heart

The development of the fetal heart is exquisitely controlled by a multitude of factors, ranging from humoral to mechanical forces. The gatekeeper regulating many of these factors is the placenta, an external fetal organ. As such, resistance within the placental vascular bed has a direct influence on the fetal circulation and therefore, the developing heart. In addition, the placenta serves as the interface between the mother and fetus, controlling substrate exchange and release of hormones into both circulations. The intricate relationship between the placenta and fetal heart is appreciated in instances of clinical placental pathology. Abnormal umbilical cord insertion is associated with congenital heart defects. Likewise, twin-to-twin transfusion syndrome, where monochorionic twins have unequal sharing of their placenta due to inter-twin vascular anastomoses, can result in cardiac remodeling and dysfunction in both fetuses. Moreover, epidemiological studies have suggested a link between placental phenotypic traits and increased risk of cardiovascular disease in adult life. To date, the mechanistic basis of the relationships between the placenta, fetal heart development and later risk of cardiac dysfunction have not been fully elucidated. However, studies using environmental exposures and gene manipulations in experimental animals are providing insights into the pathways involved. Likewise, surgical instrumentation of the maternal and fetal circulations in large animal species has enabled the manipulation of specific humoral and mechanical factors to investigate their roles in fetal cardiac development. This review will focus on such studies and what is known to date about the link between the placenta and heart development.

Hypoxic Stress Forces Adaptive and Maladaptive Placental Stress Responses in Early Pregnancy

This review focuses on hypoxic stress and its effects on the placental lineage and the earliest differentiation events in mouse and human placental trophoblast stem cells (TSCs). Although the placenta is a decidual organ at the end of pregnancy, its earliest rapid growth and function at the start of pregnancy precedes and supports growth and function of the embryo. Earliest function requires that TSCs differentiate, however, "hypoxia" supports rapid growth, but not differentiation of TSCs. Most of the literature on earliest placental "hypoxia" studies used 2% oxygen which is normoxic for TSCs. Hypoxic stress happens when oxygen level drops below 2%. It decreases anabolism, proliferation, potency/stemness and increases differentiation, despite culture conditions that would sustain proliferation and potency. Thus, to study the pathogenesis due to TSC dysfunction, it is important to study hypoxic stress below 2%. Many studies have been performed using 0.5 to 1% oxygen in cultured mouse TSCs. From all these studies, a small number has examined human trophoblast lines and primary first trimester placental hypoxic stress responses in culture. Some other stress stimuli, aside from hypoxic stress, are used to elucidate common and unique aspects of hypoxic stress. The key outcomes produced by hypoxic stress are mitochondrial, anabolic, and proliferation arrest, and this is coupled with stemness loss and differentiation. Hypoxic stress can lead to depletion of stem cells and miscarriage, or can lead to later dysfunctions in placentation and fetal development. Birth Defects Research 109:1330-1344, 2017. © 2017 Wiley Periodicals, Inc.

Hypoxia and Placental Development

Hemochorial placentation is orchestrated through highly regulated temporal and spatial decisions governing the fate of trophoblast stem/progenitor cells. Trophoblast cell acquisition of specializations facilitating invasion and uterine spiral artery remodeling is a labile process, sensitive to the environment, and represents a process that is vulnerable to dysmorphogenesis in pathologic states. Hypoxia is a signal guiding placental development, and molecular mechanisms directing cellular adaptations to low oxygen tension are integral to trophoblast cell differentiation and placentation. Hypoxia can also be used as an experimental tool to investigate regulatory processes controlling hemochorial placentation. These developmental processes are conserved in mouse, rat, and human placentation. Consequently, elements of these developmental events can be modeled and hypotheses tested in trophoblast stem cells and in genetically manipulated rodents. Hypoxia is also a consequence of a failed placenta, yielding pathologies that can adversely affect maternal adjustments to pregnancy, fetal health, and susceptibility to adult disease. The capacity of the placenta for adaptation to environmental challenges highlights the importance of its plasticity in safeguarding a healthy pregnancy. Birth Defects Research 109:1309-1329, 2017.© 2017 Wiley Periodicals, Inc.

CITED2 Restrains Proinflammatory Macrophage Activation and Response

Macrophages are strategically distributed in mammalian tissues and play an essential role in priming the immune response. However, macrophages need to constantly strike a balance between activation and inhibition states to avoid a futile inflammatory reaction. Here, we identify the CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxyl-terminal domain 2 (CITED2) as a potent repressor of macrophage proinflammatory activation. Gain- and loss-of-function studies revealed that CITED2 is required for optimal peroxisome proliferator-activated receptor gamma (PPARγ) activation and attendant select anti-inflammatory gene expression in macrophages. More importantly, deficiency of CITED2 resulted in significant attenuation of rosiglitazone-induced PPARγ activity, PPARγ recruitment to target gene promoters, and anti-inflammatory target gene expression in macrophages. Interestingly, deficiency of Cited2 strikingly heightened proinflammatory gene expression through stabilization of hypoxia-inducible factor 1 alpha (HIF1α) protein in macrophages. Further, overexpression of Egln3 or inhibition of HIF1α in Cited2-deficient macrophages completely reversed elevated proinflammatory cytokine/chemokine gene expression. Importantly, mice bearing a myeloid cell-specific deletion of Cited2 were highly susceptible to endotoxin-induced sepsis symptomatology and mortality. Collectively, our observations identify CITED2 as a novel negative regulator of macrophage proinflammatory activation that protects the host from inflammatory insults.

Current model systems for the study of preeclampsia

Preeclampsia (PE) is a pregnancy complex disease, distinguished by high blood pressure and proteinuria, diagnosed after the 20th gestation week. Depending on the values of blood pressure, urine protein concentrations, symptomatology, and onset of disease there is a wide range of phenotypes, from mild forms developing predominantly at the end of pregnancy to severe forms developing in the early stage of pregnancy. In the worst cases severe forms of PE could lead to systemic endothelial dysfunction, eclampsia, and maternal and/or fetal death. Worldwide the fetal morbidity and mortality related to PE is calculated to be around 8% of the total pregnancies. PE still being an enigma regarding its etiology and pathophysiology, in general a deficient trophoblast invasion during placentation at first stage of pregnancy, in combination with maternal conditions are accepted as a cause of endothelial dysfunction, inflammatory alterations and appearance of symptoms. Depending on the PE multifactorial origin, several in vitro, in vivo, and in silico models have been used to evaluate the PE pathophysiology as well as to identify or test biomarkers predicting, diagnosing or prognosing the syndrome. This review focuses on the most common models used for the study of PE, including those related to placental development, abnormal trophoblast invasion, uteroplacental ischemia, angiogenesis, oxygen deregulation, and immune response to maternal-fetal interactions. The advances in mathematical and computational modeling of metabolic network behavior, gene prioritization, the protein-protein interaction network, the genetics of PE, and the PE prediction/classification are discussed. Finally, the potential of these models to enable understanding of PE pathogenesis and to evaluate new preventative and therapeutic approaches in the management of PE are also highlighted. Impact statement This review is important to the field of preeclampsia (PE), because it provides a description of the principal in vitro, in vivo, and in silico models developed for the study of its principal aspects, and to test emerging therapies or biomarkers predicting the syndrome before their evaluation in clinical trials. Despite the current advance, the field still lacking of new methods and original modeling approaches that leads to new knowledge about pathophysiology. The part of in silico models described in this review has not been considered in the previous reports.

Dynamic expression of TET1, TET2, and TET3 dioxygenases in mouse and human placentas throughout gestation

INTRODUCTION

Throughout pregnancy, the placenta dynamically changes as trophoblast progenitors differentiate into mature trophoblast cell subtypes. This process is in part controlled by epigenetic regulation of DNA methylation leading to the inactivation of 'progenitor cell' genes and the activation of 'differentiation' genes. TET methylcytosine dioxygenases convert 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) during DNA demethylation events. Here, we determine the spatiotemporal expression of TET1, TET2, and TET3 in specific trophoblast cell populations of mouse and human placentas throughout gestation, and consider their role in trophoblast cell differentiation and function.

METHODS

In situ hybridization analysis was conducted to localize Tet1, Tet2, and Tet3 mRNA at key stages of mouse placental development. The distribution of 5-mC and 5-hmC in these samples was also evaluated. In comparison, expression patterns of TET1, TET2, and TET3 protein in human placentas were determined in first trimester and term pregnancies.

RESULTS

In mouse, Tet1-3 mRNA was widely expressed in trophoblast cell populations from embryonic (E) day 8.5 to E12.5 including in progenitor and differentiated cells. However, expression became restricted to specific trophoblast giant cell subtypes by late gestation (E14.5 to E18.5). This coincided with cellular changes in 5-mC and 5-hmC levels. In human, cell columns, extravillous trophoblast and syncytiotrophoblast expressed TET1-3 whereas only TET3 was expressed in villus cytotrophoblast cells in first trimester and term placentas.

DISCUSSION

Altogether, our data suggest that TET enzymes may play a dynamic role in the regulation of transcriptional activity of trophoblast progenitors and differentiated cell subtypes in mouse and human placentas.

Cited2 Regulates Neocortical Layer II/III Generation and Somatosensory Callosal Projection Neuron Development and Connectivity

The neocortex contains hundreds to thousands of distinct subtypes of precisely connected neurons, allowing it to perform remarkably complex tasks of high-level cognition. Callosal projection neurons (CPN) connect the cerebral hemispheres via the corpus callosum, integrating cortical information and playing key roles in associative cognition. CPN are a strikingly diverse set of neuronal subpopulations, and development of this diversity requires precise control by a complex, interactive set of molecular effectors. We have found that the transcriptional coregulator Cited2 regulates and refines two stages of CPN development. Cited2 is expressed broadly by progenitors in the embryonic day 15.5 subventricular zone, during the peak of superficial layer CPN birth, with a progressive postmitotic refinement in expression, becoming restricted to CPN of the somatosensory cortex postnatally. We generated progenitor-stage and postmitotic forebrain-specific Cited2 conditional knock-out mice, using the Emx1-Cre and NEX-Cre mouse lines, respectively. We demonstrate that Cited2 functions in progenitors, but is not necessary postmitotically, to regulate both (1) broad generation of layer II/III CPN and (2) acquisition of precise area-specific molecular identity and axonal/dendritic connectivity of somatosensory CPN. This novel CPN subtype-specific and area-specific control from progenitor action of Cited2 adds yet another layer of complexity to the multistage developmental regulation of neocortical development.

SIGNIFICANCE STATEMENT

This study identifies Cited2 as a novel subtype-specific and area-specific control over development of distinct subpopulations within the broad population of callosal projection neurons (CPN), whose axons connect the two cerebral hemispheres via the corpus callosum (CC). Currently, how the remarkable diversity of CPN subtypes is specified, and how they differentiate to form highly precise and specific circuits, are largely unknown. We found that Cited2 functions within subventricular zone progenitors to both broadly regulate generation of superficial layer CPN throughout the neocortex, and to refine precise area-specific development and connectivity of somatosensory CPN. Gaining insight into molecular development and heterogeneity of CPN will advance understanding of both diverse functions of CPN and of the remarkable range of neurodevelopmental deficits correlated with CPN/CC development.

At Term, XmO and XpO Mouse Placentas Show Differences in Glucose Metabolism in the Trophectoderm-Derived Outer Zone

Genetic mouse model (39,XO) for human Turner Syndrome (45,XO) harboring either a single maternally inherited (Xm) or paternally inherited (Xp) chromosome show a pronounced difference in survival rate at term. However, a detailed comparison of XmO and XpO placentas to explain this difference is lacking. We aimed to investigate the morphological and molecular differences between XmO and XpO term mouse placentas. We observed that XpO placentas at term contained a significantly larger area of glycogen cells (GCs) in their outer zone, compared to XmO, XX, and XY placentas. In addition, the outer zone of XpO placentas showed higher expression levels of lactate dehydrogenase (Ldha) than XmO, XX, and XY placentas, suggestive of increased anaerobic glycolysis. In the labyrinth, we detected significantly lower expression level of trophectoderm (TE)-marker keratin 19 (Krt19) in XpO placentas than in XX placentas. The expression of other TE-markers was comparable as well as the area of TE-derived cells between XO and wild-type labyrinths. XpO placentas exhibited specific defects in the amount of GCs and glucose metabolism in the outer zone, suggestive of increased anaerobic glycolysis, as a consequence of having inherited a single Xp chromosome. In conclusion, the XpO genotype results in a more severe placental phenotype at term, with distinct abnormalities regarding glucose metabolism in the outer zone.

CITED2 modulation of trophoblast cell differentiation: insights from global transcriptome analysis

Trophoblast stem (TS) cells possess the capacity to differentiate along a multi-lineage pathway yielding several specialized cell types. The regulatory network controlling trophoblast cell differentiation is poorly understood. Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain, 2 (CITED2) has been implicated in the regulation of placentation; however, we know little about how CITED2 acts to influence trophoblast cells. Rat Rcho-1 TS cells can be manipulated to proliferate or differentiate into specialized trophoblast lineages and are an excellent model for investigating trophoblast differentiation. CITED2 transcript and protein showed a robust induction during Rcho-1 TS cell differentiation. We used an shRNA knockdown approach to disrupt CITED2 expression in order to investigate its involvement in trophoblast cell differentiation. RNA-sequencing was used to examine the impact of CITED2 on trophoblast cell differentiation. CITED2 disruption affected the differentiating trophoblast cell transcriptome. CITED2 possessed a prominent role in the regulation of cell differentiation with links to several signal transduction pathways and to hypoxia-regulated and coagulation processes. In summary, our findings indicate that CITED2 contributes to the regulation of trophoblast cell differentiation.

The imprinted Phlda2 gene modulates a major endocrine compartment of the placenta to regulate placental demands for maternal resources

Imprinted genes, which are expressed from a single parental allele in response to epigenetic marks first established in the germline, function in a myriad of processes to regulate mammalian development. Recent work suggests that imprinted genes may regulate the signalling function of the placenta by modulating the size of the endocrine compartment. Here we provide in vivo evidence that this hypothesis is well founded. Elevated expression of the imprinted Pleckstrin homology-like domain, family a, member 2 (Phlda2) gene drives a reduction of the spongiotrophoblast endocrine compartment, diminished placental glycogen and asymmetric foetal growth restriction. Using both loss-of-function and gain-in-expression mouse models, here we further show that Phlda2 exclusively modulates the spongiotrophoblast compartment of the placenta without significantly altering the composition of the trophoblast giant cell endocrine lineages that share a common progenitor with this lineage. Additionally, we show that Phlda2 loss-of-function placentae contain nearly three times more placental glycogen than non-transgenic placentae. Remarkably, relative to a fully wild type scenario, wild type placentae also accumulate excessive glycogen. While loss-of-function of Phlda2 increased both placental weight and placental glycogen, the weight of both mutant and non-transgenic fetuses was lower than that found in a fully wild type scenario indicating that excessive glycogen accumulation comes at the cost of foetal growth. This work firstly highlights a novel signalling function for the spongiotrophoblast in stimulating the global accumulation of placental glycogen. Furthermore, this work suggests that Phlda2 manipulates the placenta's demands for maternal resources, a process that must be tightly regulated by epigenetic marks to ensure optimal foetal growth.

•

Phlda2 specifically restrains development of the spongiotrophoblast.

•

The spongiotrophoblast is a major endocrine compartment of the placenta.

•

The spongiotrophoblast locally and globally boosts glycogen accumulation.

•

Excessive glycogen accumulation is associated with foetal growth restriction.

•

Phlda2 regulates placental demands from maternal resources.

Reduced Gene Dosage of Tfap2c Impairs Trophoblast Lineage Differentiation and Alters Maternal Blood Spaces in the Mouse Placenta

Tfap2c is required for placental development and trophoblast stem cell maintenance. Deletion of Tfap2c results in early embryonic loss because of failure in placental development. We evaluated the effect of reduced Tfap2c expression on fetal outcome and placental development. Sixty percent of the heterozygous mice were lost directly after birth. Labyrinthine differentiation was impaired, as indicated by enhanced proliferation and inclusions of cobblestone-shaped cell clusters characterized by expression of Tfap2c and glycogen stores. Moreover, expression of marker genes such as Cdx2, Eomes, Gata3, and Ascl2 are decreased in the spongiotrophoblast and indicate a lowered stem cell potential. On Day 18.5 postcoitum, the labyrinth layer of Tfap2c(+/-) placentas exhibited massive hemorrhages in the maternal blood spaces; these hemorrhages might have contributed to the significantly reduced number of live-born pups. These morphological alterations were accompanied by a shift toward sinusoidal trophoblast giant cells as the cell subpopulation lining the maternal sinusoids and toward reduction in expression of the prolactin gene family member Prl2c2, a finding characteristic of the spiral arteries lining trophoblast cells. The trophoblast stem cells heterozygous for Tfap2c exhibited a reduction in the expression level of stem cell markers and in their proliferation and differentiation capacity but did not exhibit changes in marker genes of the trophoblast giant cell lineage. Taken together, these findings indicate that a reduction in the gene dosage of placental Tfap2c leads to morphological changes in the labyrinth at midgestation and in the maternal blood spaces during late pregnancy.

Adaptive mechanisms controlling uterine spiral artery remodeling during the establishment of pregnancy

Implantation of the embryo into the uterus triggers the initiation of hemochorial placentation. The hemochorial placenta facilitates the acquisition of maternal resources required for embryo/fetal growth. Uterine spiral arteries form the nutrient supply line for the placenta and fetus. This vascular conduit undergoes gestation stage-specific remodeling directed by maternal natural killer cells and embryo-derived invasive trophoblast lineages. The placentation site, including remodeling of the uterine spiral arteries, is shaped by environmental challenges. In this review, we discuss the cellular participants controlling pregnancy-dependent uterine spiral artery remodeling and mechanisms responsible for their development and function.

Expression of hypoxia-inducible factors and vascular endothelial growth factor during pregnancy in the feline uterus

Hypoxia-inducible factors (HIFs) and vascular endothelial growth factor (VEGF) have critical roles during the development of the fetomaternal unit. The HIFs regulate placentation and vascularization by stimulation of VEGF gene expression. This study aimed to investigate the expression profiles of HIF gene family and VEGF in the cat uterus during pregnancy. Tissue samples of the whole uterine wall were collected after ovariohysterectomy and allocated to the following groups: embryo positive (group 1 [G1], n = 7, 7 days after mating), early pregnancy (group 2 [G2], n = 7, 20 days after mating), mid-pregnancy (group 3 [G3], n = 7, 24 days after mating), late pregnancy (group 4 [G4], n = 7, 30-45 days after mating), and oocyte positive groups (group 5 [G5], n = 7, 7 days after induction of ovulation with GnRH analog). Relative mRNA levels were determined by real-time polymerase chain reaction. As housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase was used. The relative gene expression of HIF1A in G5 was found to be significantly higher than that of other groups (G1, G2, G3, and G4) (P < 0.05). In addition, the expression of HIF2A in G5 was higher than that of G1 and HIF2A gene expression at placentation sites of G4 was higher than in G1, G2, and G3 (P < 0.05). Immunohistochemistry indicated that HIF1A, HIF2A, and VEGF expressions were observed in different cell types of uterine and placental tissues in late pregnancy and oocyte groups. The expression of HIF3A did not change significantly in any group investigated. These observations suggest that HIFs and VEGF may play a role in the establishment and development of pregnancy.

Transcriptional regulators of the trophoblast lineage in mammals with hemochorial placentation

Mammalian reproduction is critically dependent on the trophoblast cell lineage, which assures proper establishment of maternal-fetal interactions during pregnancy. Specification of trophoblast cell lineage begins with the development of the trophectoderm (TE) in preimplantation embryos. Subsequently, other trophoblast cell types arise with the progression of pregnancy. Studies with transgenic animal models as well as trophoblast stem/progenitor cells have implicated distinct transcriptional and epigenetic regulators in trophoblast lineage development. This review focuses on our current understanding of transcriptional and epigenetic mechanisms regulating specification, determination, maintenance and differentiation of trophoblast cells.

Hectd1 is required for development of the junctional zone of the placenta

The placenta plays a critical role in the growth and survival of the fetus. Here we demonstrate that the Homologous to the E6-AP Carboxyl Terminus (HECT) domain E3 ubiquitin ligase, Hectd1, is essential for development of the mouse placenta. Hectd1 is widely expressed during placentation with enrichment in trophoblast giant cells (TGCs) and other trophoblast-derived cell subtypes in the junctional and labyrinth zones of the placenta. Disruption of Hectd1 results in mid-gestation lethality and intrauterine growth restriction (IUGR). Variable defects in the gross structure of the mutant placenta are found including alterations in diameter, thickness and lamination. The number and nuclear size of TGCs is reduced. Examination of subtype specific markers reveals altered TGC development with decreased expression of Placental lactogen-1 and -2 (Pl1 and Pl2) and increased expression of Proliferin (Plf). Reduced numbers of spongiotrophoblasts and glycogen trophoblasts were also found at the junctional zone of the Hectd1 mutant placenta. Finally, there was an increase in immature uterine natural killer (uNK) cells in the maternal decidua of the Hectd1 mutant placenta. Proliferation and apoptosis are differentially altered in the layers of the placenta with an increase in both apoptosis and proliferation in the maternal decidua, a decrease in proliferation and increase in apoptosis in the labyrinth layer and both unchanged in the junctional zone. Together these data demonstrate that Hectd1 is required for development of multiple cell types within the junctional zone of the placenta.

Isolating the role of elevated Phlda2 in asymmetric late fetal growth restriction in mice

Pleckstrin homology-like domain family A member 2 (PHLDA2) is a maternally expressed imprinted gene whose elevated expression has been linked to fetal growth restriction in a number of human studies. In mice, Phlda2 negatively regulates placental growth and limits the accumulation of placental glycogen. We previously reported that a three-copy transgene spanning the Phlda2 locus drove a fetal growth restriction phenotype late in gestation, suggesting a causative role for PHLDA2 in human growth restriction. However, in this mouse model, Phlda2 was overexpressed by fourfold, alongside overexpression of a second imprinted gene, Slc22a18. Here, we genetically isolate the role of Phlda2 in driving late fetal growth restriction in mice. We furthermore show that this Phlda2-driven growth restriction is asymmetrical, with a relative sparing of the brain, followed by rapid catch-up growth after birth, classic features of placental insufficiency. Strikingly, fetal growth restriction showed strain-specific differences, being apparent on the 129S2/SvHsd (129) genetic background and absent on the C57BL6 (BL6) background. A key difference between these two strains is the placenta. Specifically, BL6 placentae possess a more extensive endocrine compartment and substantially greater stores of placental glycogen. Taken together, these data support a direct role for elevated Phlda2 in limiting fetal growth but also suggest that growth restriction only manifests when there is limited placental reserve. These findings should be taken into account in interpreting the results from human studies.

Vulnerability of the developing heart to oxygen deprivation as a cause of congenital heart defects

Background

The heart develops under reduced and varying oxygen concentrations, yet there is little understanding of oxygen metabolism in the normal and mal‐development of the heart. Here we used a novel reagent, the ODD‐Luc hypoxia reporter mouse (oxygen degradation domain, ODD) of Hif‐1α fused to Luciferase (Luc), to assay the activity of the oxygen sensor, prolyl hydroxylase, and oxygen reserve, in the developing heart. We tested the role of hypoxia‐dependent responses in heart development by targeted inactivation of Hif‐1α.

Methods and Results

ODD‐Luciferase activity was 14‐fold higher in mouse embryonic day 10.5 (E10.5) versus adult heart and liver tissue lysates. ODD‐Luc activity decreased in 2 stages, the first corresponding with the formation of a functional cardiovascular system for oxygen delivery at E15.5, and the second after birth consistent with complete oxygenation of the blood and tissues. Reduction of maternal inspired oxygen to 8% for 4 hours caused minimal induction of luciferase activity in the maternal tissues but robust induction in the embryonic tissues in proportion to the basal activity, indicating a lack of oxygen reserve, and corresponding induction of a hypoxia‐dependent gene program. Bioluminescent imaging of intact embryos demonstrated highest activity in the outflow portion of the E13.5 heart. Hif‐1α inactivation or prolonged hypoxia caused outflow and septation defects only when targeted to this specific developmental window.

Conclusions

Low oxygen concentrations and lack of oxygen reserve during a critical phase of heart organogenesis may provide a basis for vulnerability to the development of common septation and conotruncal heart defects.

Development of the hemochorial maternal vascular spaces in the placenta through endothelial and vasculogenic mimicry

The maternal vasculature within the placenta in primates and rodents is unique because it is lined by fetal cells of the trophoblast lineage and not by maternal endothelial cells. In addition to trophoblast cells that invade the uterine spiral arteries that bring blood into the placenta, other trophoblast subtypes sit at different levels of the vascular space. In mice, at least five distinct subtypes of trophoblast cells have been identified which engage maternal endothelial cells on the arterial and venous frontiers of the placenta, but which also form the channel-like spaces within it through a process analogous to formation of blood vessels (vasculogenic mimicry). These cells are all large, post-mitotic trophoblast giant cells. In addition to assuming endothelial cell-like characteristics (endothelial mimicry), they produce dozens of different hormones that are thought to regulate local and systemic maternal adaptations to pregnancy. Recent work has identified distinct molecular pathways in mice that regulate the morphogenesis of trophoblast cells on the arterial and venous sides of the vascular circuit that may be analogous to specification of arterial and venous endothelial cells.

The effect of gestational age on angiogenic gene expression in the rat placenta

The placenta plays a central role in determining the outcome of pregnancy. It undergoes changes during gestation as the fetus develops and as demands for energy substrate transfer and gas exchange increase. The molecular mechanisms that coordinate these changes have yet to be fully elucidated. The study performed a large scale screen of the transcriptome of the rat placenta throughout mid-late gestation (E14.25–E20) with emphasis on characterizing gestational age associated changes in the expression of genes invoved in angiogenic pathways. Sprague Dawley dams were sacrificed at E14.25, E15.25, E17.25 and E20 (n = 6 per group) and RNA was isolated from one placenta per dam. Changes in placental gene expression were identifed using Illumina Rat Ref-12 Expression BeadChip Microarrays. Differentially expressed genes (>2-fold change, <1% false discovery rate, FDR) were functionally categorised by gene ontology pathway analysis. A subset of differentially expressed genes identified by microarrays were confirmed using Real-Time qPCR. The expression of thirty one genes involved in the angiogenic pathway was shown to change over time, using microarray analysis (22 genes displayed increased and 9 gene decreased expression). Five genes (4 up regulated: Cd36, Mmp14, Rhob and Angpt4 and 1 down regulated: Foxm1) involved in angiogenesis and blood vessel morphogenesis were subjected to further validation. qPCR confirmed late gestational increased expression of Cd36, Mmp14, Rhob and Angpt4 and a decrease in expression of Foxm1 before labour onset (P<0.0001). The observed acute, pre-labour changes in the expression of the 31 genes during gestation warrant further investigation to elucidate their role in pregnancy.

Hypoxia and HIFs in regulating the development of the hematopoietic system

Many physiologic processes during the early stages of mammalian ontogeny, particularly placental and vascular development, take place in the low oxygen environment of the uterus. Organogenesis is affected by hypoxia inducible factor (HIF) transcription factors that are sensors of hypoxia. In response to hypoxia, HIFs activate downstream target genes - growth and metabolism factors. During hematopoietic system ontogeny, blood cells and hematopoietic progenitor/stem cells are respectively generated from mesodermal precursors, hemangioblasts, and from a specialized subset of endothelial cells that are hemogenic. Since HIFs are known to play a central role in vascular development, and hematopoietic system development occurs in parallel to that of the vascular system, several studies have examined the role of HIFs in hematopoietic development. The response to hypoxia has been examined in early and mid-gestation mouse embryos through genetic deletion of HIF subunits. We review here the data showing that hematopoietic tissues of the embryo are hypoxic and express HIFs and HIF downstream targets, and that HIFs regulate the development and function of hematopoietic progenitor/stem cells.

A cell-autonomous role of Cited2 in controlling myocardial and coronary vascular development

AIMS

Myocardial development is dependent on concomitant growth of cardiomyocytes and a supporting vascular network. The coupling of myocardial and coronary vascular development is partly mediated by vascular endothelial growth factor (VEGFA) signalling and additional unknown mechanisms. We examined the cardiomyocyte specific role of the transcriptional co-activator Cited2 on myocardial microstructure and vessel growth, in relation to Vegfa expression.

METHODS AND RESULTS

A cardiomyocyte-specific knockout of mouse Cited2 (Cited2(Nkx)) was analysed using magnetic resonance imaging and histology. Ventricular septal defects and significant compact layer thinning (P < 0.02 at right ventricular apex, P < 0.009 at the left ventricular apex in Cited2(Nkx) vs. controls, n = 11 vs. n = 7, respectively) were found. This was associated with a significant decrease in the number of capillaries to larger vessels (ratio 1.56 ± 0.56 vs. 3.25 ± 1.63, P = 2.7 × 10(-6) Cited2(Nkx) vs. controls, n = 11 vs. n = 7, respectively) concomitant with a 1.5-fold reduction in Vegfa expression (P < 0.02, Cited2(Nkx) vs. controls, n = 12 vs. n = 12, respectively). CITED2 was subsequently found at the Vegfa promoter in mouse embryonic hearts using chromatin immunoprecipitation, and moreover found to stimulate human VEGFA promoter activity in cooperation with TFAP2 transcription factors in transient transfection assays. There was no change in the myocardial expression of the left-right patterning gene Pitx2c, a previously known target of CITED2.

CONCLUSIONS

This study delineates a novel cell-autonomous role of Cited2 in regulating VEGFA transcription and the development of myocardium and coronary vasculature in the mouse. We suggest that coupling of myocardial and coronary growth in the developing heart may occur in part through a Cited2→Vegfa pathway.

Cardiac gene activation analysis in mammalian non-myoblasic cells by Nkx2-5, Tbx5, Gata4 and Myocd

Cardiac transcription factors are master regulators during heart development. Some were shown to transdifferentiate tail tip and cardiac fibroblasts into cardiomyocytes. However, recent studies have showed that controversies exist. Potential difference in tail tip and cardiac fibroblast isolation may possibly confound the observations. Moreover, due to the use of a cardiac reporter (Myh6) selection strategy for induced cardiomyocyte enrichment, and the lack of tracking signals for each transcription factors, individual roles of each transcription factors in activating cardiac gene expression in mammalian non-myoblastic cells have never been elucidated. Answers to these questions are an important step toward cardiomyocyte regeneration. Because mouse 10T1/2 fibroblasts are non-myoblastic in nature and can be induced to express genes of all three types of muscle cells, they are an ideal model for the analysis of cardiac and non-cardiac gene activation after induction. We constructed bi-cistronic lentiviral vectors, capable of expressing cardiac transcription factors along with different fluorescent tracking signals. By infecting 10T1/2 fibroblasts with Nkx2-5, Tbx5, Gata4 or Myocd cardiac transcription factor lentivirus alone or different combinations, we found that only Tbx5+Myocd and Tbx5+Gata4+Myocd combinations induced Myh6 and Tnnt2 cardiac marker protein expression. Microarray-based gene ontology analysis revealed that Tbx5 alone activated genes involved in the Wnt receptor signaling pathway and inhibited genes involved in a number of cardiac-related processes. Myocd alone activated genes involved in a number of cardiac-related processes and inhibited genes involved in the Wnt receptor signaling pathway and non-cardiac processes. Gata4 alone inhibited genes involved in non-cardiac processes. Tbx5+Gata4+Myocd was the most effective activator of genes associated with cardiac-related processes. Unlike Tbx5, Gata4, Myocd alone or Tbx5+Myocd, Tbx5+Gata4+Myocd activated the fewest genes associated with non-cardiac processes. Conclusively, Tbx5, Gata4 and Myocd play different roles in cardiac gene activation in mammalian non-myoblastic cells. Tbx5+Gata4+Myocd activates the most cardiac and the least non-cardiac gene expression.