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

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.

Increased dosage of the imprinted Ascl2 gene restrains two key endocrine lineages of the mouse Placenta

Imprinted genes are expressed primarily from one parental allele by virtue of a germ line epigenetic process. Achaete-scute complex homolog 2 (Ascl2 aka Mash2) is a maternally expressed imprinted gene that plays a key role in placental and intestinal development. Loss-of-function of Ascl2 results in an expansion of the parietal trophoblast giant cell (P-TGC) lineage, an almost complete loss of Trophoblast specific protein alpha (Tpbpa) positive cells in the ectoplacental cone and embryonic failure by E10.5. Tpbpa expression marks the progenitors of some P-TGCs, two additional trophoblast giant cell lineages (spiral artery and canal), the spongiotrophoblast and the glycogen cell lineage. Using a transgenic model, here we show that elevated expression of Ascl2 reduced the number of P-TGC cells by 40%. Elevated Ascl2 also resulted in a marked loss of the spongiotrophoblast and a substantial mislocalisation of glycogen cells into the labyrinth. In addition, Ascl2-Tg placenta contained considerably more placental glycogen than wild type. Glycogen cells are normally located within the junctional zone in close contact with spongiotrophoblast cells, before migrating through the P-TGC layer into the maternal decidua late in gestation where their stores of glycogen are released. The failure of glycogen cells to release their stores of glycogen may explain both the inappropriate accumulation of glycogen and fetal growth restriction observed late in gestation in this model. In addition, using in a genetic cross we provide evidence that Ascl2 requires the activity of a second maternally expressed imprinted gene, Pleckstrin homology-like domain, family a, member 2 (Phlda2) to limit the expansion of the spongiotrophoblast. This "belts and braces" approach demonstrates the importance of genomic imprinting in regulating the size of the placental endocrine compartment for optimal placental development and fetal growth.

Id2 Mediates Differentiation of Labyrinthine Placental Progenitor Cell Line, SM10

The placenta is an organ that is formed transiently during pregnancy, and appropriate placental development is necessary for fetal survival and growth. Proper differentiation of the labyrinthine layer of the placenta is especially crucial, as it establishes the fetal-maternal interface that is involved in physiological exchange processes. Although previous studies have indicated the importance of inhibitor of differentiation/inhibitor of DNA binding-2 (Id2) helix-loop-helix transcriptional regulator in mediating cell differentiation, the ability of Id2 to regulate differentiation toward the labyrinthine (transport) lineage of the placenta has yet to be determined. In the current study, we have generated labyrinthine trophoblast progenitor cells with increased (SM10-Id2) or decreased (SM10-Id2-shRNA) Id2 expression and determined the effect on TGF-β-induced differentiation. Our Id2 overexpression and knockdown analyses indicate that Id2 mediates TGF-β-induced morphological differentiation of labyrinthine trophoblast cells, as Id2 overexpression prevents differentiation and Id2 knockdown results in differentiation. Thus, our data indicate that Id2 is an important molecular mediator of labyrinthine trophoblast differentiation. An understanding of the regulators of trophoblast progenitor differentiation toward the labyrinthine lineage may offer insights into events governing pregnancy-associated disorders, such as placental insufficiency, fetal growth restriction, and preeclampsia.

Induction of specific neuron types by overexpression of single transcription factors

Specific neuronal types derived from embryonic stem cells (ESCs) can facilitate mechanistic studies and potentially aid in regenerative medicine. Existing induction methods, however, mostly rely on the effects of the combined action of multiple added growth factors, which generally tend to result in mixed populations of neurons. Here, we report that overexpression of specific transcription factors (TFs) in ESCs can rather guide the differentiation of ESCs towards specific neuron lineages. Analysis of data on gene expression changes 2 d after induction of each of 185 TFs implicated candidate TFs for further ESC differentiation studies. Induction of 23 TFs (out of 49 TFs tested) for 6 d facilitated neural differentiation of ESCs as inferred from increased proportion of cells with neural progenitor marker PSA-NCAM. We identified early activation of the Notch signaling pathway as a common feature of most potent inducers of neural differentiation. The majority of neuron-like cells generated by induction of Ascl1, Smad7, Nr2f1, Dlx2, Dlx4, Nr2f2, Barhl2, and Lhx1 were GABA-positive and expressed other markers of GABAergic neurons. In the same way, we identified Lmx1a and Nr4a2 as inducers for neurons bearing dopaminergic markers and Isl1, Fezf2, and St18 for cholinergic motor neurons. A time-course experiment with induction of Ascl1 showed early upregulation of most neural-specific messenger RNA (mRNA) and microRNAs (miRNAs). Sets of Ascl1-induced mRNAs and miRNAs were enriched in Ascl1 targets. In further studies, enrichment of cells obtained with the induction of Ascl1, Smad7, and Nr2f1 using microbeads resulted in essentially pure population of neuron-like cells with expression profiles similar to neural tissues and expressed markers of GABAergic neurons. In summary, this study indicates that induction of transcription factors is a promising approach to generate cultures that show the transcription profiles characteristic of specific neural cell types.

Capturing Identity and Fate Ex Vivo: Stem Cells from the Mouse Blastocyst

During mouse preimplantation development, three molecularly, morphologically, and spatially distinct lineages are formed, the embryonic epiblast, the extraembryonic primitive endoderm, and the trophectoderm. Stem cell lines representing each of these lineages have now been derived and can be indefinitely maintained and expanded in culture, providing an unlimited source of material to study the interplay of tissue-specific transcription factors and signaling pathways involved in these fundamental cell fate decisions. Here we outline our current understanding of the derivation, maintenance, and properties of these in vitro stem cell models representing the preimplantation embryonic lineages.

Sustained Endocrine Gland-Derived Vascular Endothelial Growth Factor Levels Beyond the First Trimester of Pregnancy Display Phenotypic and Functional Changes Associated With the Pathogenesis of Pregnancy-Induced Hypertension

Pregnancy-induced hypertension diseases are classified as gestational hypertension, preeclampsia, or eclampsia. The mechanisms of their development and prediction are still to be discovered. Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) is an angiogenic factor secreted by the placenta during the first trimester of human pregnancy that was shown to control trophoblast invasion, to be upregulated by hypoxia, and to be abnormally elevated in pathological pregnancies complicated with preeclampsia and intrauterine growth restriction. These findings suggested that sustaining EG-VEGF levels beyond the first trimester of pregnancy may contribute to pregnancy-induced hypertension. To test this hypothesis, osmotic minipumps delivering EG-VEGF were implanted subcutaneously into gravid OF1 (Oncins France 1) mice on day 11.5 post coitus, which is equivalent to the end of the first trimester of human pregnancy. Mice were euthanized at 15.5 and 18.5 days post coitus to assess (1) litter size, placental, and fetal weights; (2) placental histology and function; (3) maternal blood pressure; (4) renal histology and function; and (5) circulating soluble fms-like tyrosine kinase 1 and soluble endoglin. Increased EG-VEGF levels caused significant defects in placental organization and function. Both increased hypoxia and decreased trophoblast invasion were observed. Treated mice had elevated circulating soluble fms-like tyrosine kinase 1 and soluble endoglin and developed gestational hypertension with dysregulated maternal kidney function. EG-VEGF effect on the kidney function was secondary to its effects on the placenta as similarly treated male mice had normal kidney functions. Altogether, these data provide a strong evidence to confirm that sustained EG-VEGF beyond the first trimester of pregnancy contributes to the development of pregnancy-induced hypertension.

Abnormal labyrinthine zone in the Hectd1-null placenta

INTRODUCTION

The labyrinthine zone of the placenta is where exchange of nutrients and waste occurs between maternal and fetal circulations. Proper development of the placental labyrinth is essential for successful growth of the developing fetus and abnormalities in placental development are associated with intrauterine growth restriction (IUGR), preeclampsia and fetal demise. Our previous studies demonstrate that Hectd1 is essential for development of the junctional and labyrinthine zones of the placenta. Here we further characterize labyrinthine zone defects in the Hectd1 mutant placenta.

METHODS

The structure of the mutant placenta was compared to wildtype littermates using histological methods. The expression of cell type specific markers was examined by immunohistochemistry and in situ hybridization.

RESULTS

Hectd1 is expressed in the labyrinthine zone throughout development and the protein is enriched in syncytiotrophoblast layer type I cells (SynT-I) and Sinusoidal Trophoblast Giant cells (S-TGCs) in the mature placenta. Mutation of Hectd1 results in pale placentas with frequent hemorrhages along with gross abnormalities in the structure of the labyrinthine zone including a smaller overall volume and a poorly elaborated fetal vasculature that contain fewer fetal blood cells. Examination of molecular markers of labyrinthine trophoblast cell types reveals increased Dlx3 positive cells and Syna positive SynT-I cells, along with decreased Hand1 and Ctsq positive sinusoidal trophoblast giant cells (S-TGCs).

DISCUSSION

Together these defects indicate that Hectd1 is required for development of the labyrinthine zonethe mouse placenta.

Placental development in a mouse model of spinal muscular atrophy

Spinal Muscular Atrophy (SMA) is an autosomal recessive disorder, leading to fatal loss of motor neurons. It is caused by loss of function of the SMN gene, which is expressed throughout the body, and there is increasing evidence of dysfunction in non-neuronal tissues. Birthweight is one of most powerful prognostic factors for infants born with SMA, and intrauterine growth restriction is common. In the SMNΔ7 mouse model of SMA, pups with the disease lived 25% longer when their mothers were fed a higher fat, "breeder" diet. The placenta is responsible for transport of nutrients from mother to fetus, and is a major determinant of fetal growth. Thus, the present study tested the hypothesis that placental development is impaired in SMNΔ7 conceptuses. Detailed morphological characterization revealed no defects in SMNΔ7 placental development, and expression of key transcription factors regulating mouse placental development was unaffected. The intrauterine growth restriction observed in SMA infants likely does not result from impaired placental development.

Sex Specification and Heterogeneity of Primordial Germ Cells in Mice

In mice, primordial germ cells migrate into the genital ridges by embryonic day 13.5 (E13.5), where they are then subjected to a sex-specific fate with female and male primordial germ cells undergoing mitotic arrest and meiosis, respectively. However, the sex-specific basis of primordial germ cell differentiation is poorly understood. The aim of this study was to investigate the sex-specific features of mouse primordial germ cells. We performed RNA-sequencing (seq) of E13.5 female and male mouse primordial germ cells using next-generation sequencing. We identified 651 and 428 differentially expressed transcripts (>2-fold, P < 0.05) in female and male primordial germ cells, respectively. Of these, many transcription factors were identified. Gene ontology and network analysis revealed differing functions of the identified female- and male-specific genes that were associated with primordial germ cell acquisition of sex-specific properties required for differentiation into germ cells. Furthermore, DNA methylation and ChIP-seq analysis of histone modifications showed that hypomethylated gene promoter regions were bound with H3K4me3 and H3K27me3. Our global transcriptome data showed that in mice, primordial germ cells are decisively assigned to a sex-specific differentiation program by E13.5, which is necessary for the development of vital germ cells.

Changes in the enhancer landscape during early placental development uncover a trophoblast invasion gene-enhancer network

INTRODUCTION

Trophoblast invasion establishes adequate blood flow between mother and fetus in early placental development. However, little is known about the cis-regulatory mechanisms underlying this important process. We aimed to identify enhancer elements that are active during trophoblast invasion, and build a trophoblast invasion gene-enhancer network.

METHODS

We carried out ChIP-Seq for an enhancer-associated mark (H3k27Ac) at two time points during early placental development in mouse. One time point when invasion is at its peak (e7.5) and another time point shortly afterwards (e9.5). We use computational analysis to identify putative enhancers, as well as the transcription factor binding sites within them, that are specific to the time point of trophoblast invasion.

RESULTS

We compared read profiles at e7.5 and e9.5 to identify 1,977 e7.5-specific enhancers. Within a subset of e7.5-specific enhancers, we discovered a cell migration associated regulatory code, consisting of three transcription factor motifs: AP1, Ets, and Tcfap2. To validate differential expression of the transcription factors that bind these motifs, we performed RNA-Seq in the same context. Finally, we integrated these data with publicly available protein-protein interaction data and constructed a trophoblast invasion gene-enhancer network.

DISCUSSION

The data we generated and analysis we carried out improves our understanding of the regulatory mechanisms of trophoblast invasion, by suggesting a transcriptional code exists in the enhancers of cell migration genes. Furthermore, the network we constructed highlights novel candidate genes that may be critical for trophoblast invasion.

Partial Loss of Genomic Imprinting Reveals Important Roles for Kcnq1 and Peg10 Imprinted Domains in Placental Development

Mutations in imprinted genes or their imprint control regions (ICRs) produce changes in imprinted gene expression and distinct abnormalities in placental structure, indicating the importance of genomic imprinting to placental development. We have recently shown that a very broad spectrum of placental abnormalities associated with altered imprinted gene expression occurs in the absence of the oocyte-derived DNMT1o cytosine methyltransferase, which normally maintains parent-specific imprinted methylation during preimplantation. The absence of DNMT1o partially reduces inherited imprinted methylation while retaining the genetic integrity of imprinted genes and their ICRs. Using this novel system, we undertook a broad and inclusive approach to identifying key ICRs involved in placental development by correlating loss of imprinted DNA methylation with abnormal placental phenotypes in a mid-gestation window (E12.5-E15.5). To these ends we measured DNA CpG methylation at 15 imprinted gametic differentially methylated domains (gDMDs) that overlap known ICRs using EpiTYPER-mass array technology, and linked these epigenetic measurements to histomorphological defects. Methylation of some imprinted gDMDs, most notably Dlk1, was nearly normal in mid-gestation DNMT1o-deficient placentas, consistent with the notion that cells having lost methylation on these DMDs do not contribute significantly to placental development. Most imprinted gDMDs however showed a wide range of methylation loss among DNMT1o-deficient placentas. Two striking associations were observed. First, loss of DNA methylation at the Peg10 imprinted gDMD associated with decreased embryonic viability and decreased labyrinthine volume. Second, loss of methylation at the Kcnq1 imprinted gDMD was strongly associated with trophoblast giant cell (TGC) expansion. We conclude that the Peg10 and Kcnq1 ICRs are key regulators of mid-gestation placental function.

Label-free and non-invasive monitoring of porcine trophoblast derived cells: differentiation in serum and serum-free media

Traditional approaches to characterize stem cell differentiation are time-consuming, lengthy and invasive. Here, Raman microspectroscopy (RM) and atomic force microscopy (AFM) - both considered as non-invasive techniques - are applied to detect the biochemical and biophysical properties of trophoblast derived stem-like cells incubated up to 10 days under conditions designed to induce differentiation. Significant biochemical and biophysical differences between control cells and differentiated cells were observed. Quantitative real time PCR was also applied to analyze gene expression. The relationship between cell differentiation and associated cellular biochemical and biomechanical changes were discussed. Monitoring trophoblast cells differentiation.

Human cytomegalovirus infection interferes with the maintenance and differentiation of trophoblast progenitor cells of the human placenta

Human cytomegalovirus (HCMV) is a major cause of birth defects that include severe neurological deficits, hearing and vision loss, and intrauterine growth restriction. Viral infection of the placenta leads to development of avascular villi, edema, and hypoxia associated with symptomatic congenital infection. Studies of primary cytotrophoblasts (CTBs) revealed that HCMV infection impedes terminal stages of differentiation and invasion by various molecular mechanisms. We recently discovered that HCMV arrests earlier stages involving development of human trophoblast progenitor cells (TBPCs), which give rise to the mature cell types of chorionic villi-syncytiotrophoblasts on the surfaces of floating villi and invasive CTBs that remodel the uterine vasculature. Here, we show that viral proteins are present in TBPCs of the chorion in cases of symptomatic congenital infection. In vitro studies revealed that HCMV replicates in continuously self-renewing TBPC lines derived from the chorion and alters expression and subcellular localization of proteins required for cell cycle progression, pluripotency, and early differentiation. In addition, treatment with a human monoclonal antibody to HCMV glycoprotein B rescues differentiation capacity, and thus, TBPCs have potential utility for evaluation of the efficacies of novel antiviral antibodies in protecting and restoring placental development. Our results suggest that HCMV replicates in TBPCs in the chorion in vivo, interfering with the earliest steps in the growth of new villi, contributing to virus transmission and impairing compensatory development. In cases of congenital infection, reduced responsiveness of the placenta to hypoxia limits the transport of substances from maternal blood and contributes to fetal growth restriction.

IMPORTANCE

Human cytomegalovirus (HCMV) is a leading cause of birth defects in the United States. Congenital infection can result in permanent neurological defects, mental retardation, hearing loss, visual impairment, and pregnancy complications, including intrauterine growth restriction, preterm delivery, and stillbirth. Currently, there is neither a vaccine nor any approved treatment for congenital HCMV infection during gestation. The molecular mechanisms underlying structural deficiencies in the placenta that undermine fetal development are poorly understood. Here we report that HCMV replicates in trophoblast progenitor cells (TBPCs)-precursors of the mature placental cells, syncytiotrophoblasts and cytotrophoblasts, in chorionic villi-in clinical cases of congenital infection. Virus replication in TBPCs in vitro dysregulates key proteins required for self-renewal and differentiation and inhibits normal division and development into mature placental cells. Our findings provide insights into the underlying molecular mechanisms by which HCMV replication interferes with placental maturation and transport functions.

Transcriptomics of maternal and fetal membranes can discriminate between gestational-age matched preterm neonates with and without cognitive impairment diagnosed at 18-24 months

BACKGROUND

Neurocognitive impairment among children born preterm may arise from complex interactions between genes and the intra-uterine environment.

OBJECTIVES

(1) To characterize the transcriptomic profiles of chorioamniotic membranes in preterm neonates with and without neurocognitive impairment via microarrays and (2) to determine if neonates with neurocognitive impairment can be identified at birth.

MATERIALS/METHODS

A retrospective case-control study was conducted to examine the chorioamniotic transcriptome of gestational-age matched very preterm neonates with and without neurocognitive impairment at 18-24 months' corrected-age defined by a Bayley-III Cognitive Composite Score <80 (n = 14 each). Pathway analysis with down-weighting of overlapping genes (PADOG) was performed to identify KEGG pathways relevant to the phenotype. Select differentially expressed genes were profiled using qRT-PCR and a multi-gene disease prediction model was developed using linear discriminant analysis. The model's predictive performance was tested on a new set of cases and controls (n = 19 each).

RESULTS

1) 117 genes were differentially expressed among neonates with and without subsequent neurocognitive impairment (p<0.05 and fold change >1.5); 2) Gene ontology analysis indicated enrichment of 19 biological processes and 3 molecular functions; 3)PADOG identified 4 significantly perturbed KEGG pathways: oxidative phosphorylation, Parkinson's disease, Alzheimer's disease and Huntington's disease (q-value <0.1); 4) 48 of 90 selected differentially expressed genes were confirmed by qRT-PCR, including genes implicated in energy metabolism, neuronal signaling, vascular permeability and response to injury (e.g., up-regulation of SEPP1, APOE, DAB2, CD163, CXCL12, VWF; down-regulation of HAND1, OSR1)(p<0.05); and 5) a multi-gene model predicted 18-24 month neurocognitive impairment (using the ratios of OSR1/VWF and HAND1/VWF at birth) in a larger, independent set (sensitivity = 74%, at specificity = 83%).

CONCLUSIONS

Gene expression patterns in the chorioamniotic membranes link neurocognitive impairment in preterm infants to neurodegenerative disease pathways and might be used to predict neurocognitive impairment. Further prospective studies are needed.

Maternal nutrition modifies trophoblast giant cell phenotype and fetal growth in mice

Mammalian placentation is dependent upon the action of trophoblast cells at the time of implantation. Appropriate fetal growth, regulated by maternal nutrition and nutrient transport across the placenta, is a critical factor for adult offspring long-term health. We have demonstrated that a mouse maternal low-protein diet (LPD) fed exclusively during preimplantation development (Emb-LPD) increases offspring growth but programmes adult cardiovascular and metabolic disease. In this study, we investigate the impact of maternal nutrition on post-implantation trophoblast phenotype and fetal growth. Ectoplacental cone explants were isolated at day 8 of gestation from female mice fed either normal protein diet (NPD: 18% casein), LPD (9% casein) or Emb-LPD and cultured in vitro. We observed enhanced spreading and cell division within proliferative and secondary trophoblast giant cells (TGCs) emerging from explants isolated from LPD-fed females when compared with NPD and Emb-LPD explants after 24 and 48 h. Moreover, both LPD and Emb-LPD explants showed substantial expansion of TGC area during 24–48 h, not observed in NPD. No difference in invasive capacity was observed between treatments using Matrigel transwell migration assays. At day 17 of gestation, LPD- and Emb-LPD-fed conceptuses displayed smaller placentas and larger fetuses respectively, resulting in increased fetal:placental ratios in both groups compared with NPD conceptuses. Analysis of placental and yolk sac nutrient signalling within the mammalian target of rapamycin complex 1 pathway revealed similar levels of total and phosphorylated downstream targets across groups. These data demonstrate that early post-implantation embryos modify trophoblast phenotype to regulate fetal growth under conditions of poor maternal nutrition.

Isolation and characterization of trophoblast-derived stem-like cells from peri-implantation porcine embryos

In mammals, the trophoblast lineage of the embryo is specified before attachment/implantation to become the fetal portion of the placenta. Trophoblast-derived cells were isolated and cultured from day 10 and day 13 porcine embryos and were grown in vitro in a defined, serum-free culture medium for over 2 years without showing any signs of senescence. However, trophoblast-derived cells placed into serum-containing medium rapidly senesce and fail to proliferate. Semiquantitative and quantitative gene expression analyses of cells in culture from 0 to 30 days confirmed the presence (and relative abundance) of mRNA transcripts from genes involved in trophoblast function (CDX2, TEAD4, CYP17A1, HSD17B1, FGFR2, PLET, HAND1) as well as some genes known to mediate pluripotency (POU5F1, KLF4, CMYC). Protein immunolocalization demonstrated expression of both trophoblast and mesenchymal cell markers. DNA methylation patterns in promoters of three critical developmental genes (HAND1, KLF4, TEAD4) did not change appreciably over 4 months of culture in vitro. It was demonstrated that these trophoblast-derived cells are easily stably transfected with an exogenous transgene (eGFP) by a variety of methods, and show the ability to survive and to be passaged repeatedly after transfection. In summary, early embryonic porcine trophoblast-derived cells have demonstrated unique characteristics, which means they could be used as valuable tools for laboratory work. Anticipated applications include the study of trophoblast physiology as well as possible solutions for improving efficiency of transgenesis by somatic cell nuclear transfer and for pluripotency reprogramming of cells.

Three-dimensional cultures of trophoblast stem cells autonomously develop vascular-like spaces lined by trophoblast giant cells

The maternal blood space in the mouse placenta is lined not by endothelial cells but rather by various subtypes of trophoblast giant cells (TGCs), defined by their location and different patterns of gene expression. While TGCs invade the spiral arteries to displace the maternal endothelium, the rest of the vascular space is created de novo but the mechanisms are not well understood. We cultured mouse trophoblast stem (TS) cells in suspension and found that they readily form spheroids (trophospheres). Compared to cells grown in monolayer, differentiating trophospheres showed accelerated expression of TGC-specific genes. Morphological and gene expression studies showed that cavities form within the trophospheres that are primarily lined by Prl3d1/Pl1α-positive cells analogous to parietal-TGCs (P-TGCs) which line the maternal venous blood within the placenta. Lumen formation in trophospheres and in vivo was associated with cell polarization including CD34 sialomucin deposition on the apical side and cytoskeletal rearrangement. While P-TGCs preferentially formed in trophospheres at atmospheric oxygen levels (19%), decreasing oxygen to 3% shifted differentiation towards Ctsq-positive sinusoidal and/or channel TGCs. These studies show that trophoblast cells have the intrinsic ability to form vascular channels in ways analogous to endothelial cells. The trophosphere system will be valuable for assessing mechanisms that regulate specification of different TGC subtypes and their morphogenesis into vascular spaces.

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.

Stem cells marked by the R-spondin receptor LGR5

Since the discovery of LGR5 as a marker of intestinal stem cells, the field has developed explosively and led to many new avenues of research. The inner workings of the intestinal crypt stem cell niche are now well understood. The study of stem cell-enriched genes has uncovered some previously unknown aspects of the Wnt signaling pathway, the major driver of crypt dynamics. LGR5(+) stem cells can now be cultured over long periods in vitro as epithelial organoids or "mini-guts." This technology opens new possibilities of using cultured adult stem cells for drug development, disease modeling, gene therapy, and regenerative medicine. This review describes the rediscovery of crypt base columnar cells as LGR5(+) adult stem cells and summarizes subsequent progress, promises, unresolved issues, and challenges of the field.

Integrative epigenome analysis identifies a Polycomb-targeted differentiation program as a tumor-suppressor event epigenetically inactivated in colorectal cancer

Aberrant DNA hypermethylation in human cancer has been associated with Polycomb target genes in embryonic stem (ES) cells, but a functional link of the Polycomb-targeted differentiation program to tumorigenesis remains to be established. Here, through epigenome analysis correlating DNA hypermethylation in colon cancer with ES cell pluripotency and differentiation, we identified a set of DNA hypermethylated genes in cancer cells that are Polycomb targets strongly associated with ES cell differentiation, including HAND1, a developmental regulator. Intriguingly, HAND1 is silenced in over 90% of human primary colorectal tumors, and re-expression of HAND1 in colon cancer cells induces terminal differentiation, inhibits proliferation and prevents xenograft tumor formation. Moreover, hypermethylated HAND1 has a minimum enrichment of EZH2-H3K27me3 in cancer cells, but becomes EZH2 bound and bivalent upon the loss of DNA methylation, suggesting a sequential gene silencing event during oncogenesis. These findings established a functional role of Polycomb-targeted differentiation program as a tumor-suppressor event epigenetically inactivated in human cancer.

Characterization of the adverse effects of nicotine on placental development: in vivo and in vitro studies

In utero exposure to nicotine is associated with increased risk of numerous adverse fetal and neonatal outcomes, which suggests that it acts directly to affect placental development and the establishment of the fetomaternal circulation (FC). This study used both in vivo [Wistar rats treated with 1 mg/kg nicotine from 2 wk prior to mating until gestational day (GD) 15] and in vitro (RCHO-1 cell line; treated with 10(-9) to 10(-3)M nicotine) models to examine the effects of nicotine on these pathways. At GD 15, control and treated placentas were examined for the impact of nicotine on 1) trophoblast invasion, proliferation, and degree of hypoxia, 2) labyrinth vascularization, 3) expression of key genes of placental development, and 4) expression of placental angiogenic factors. The RCHO-1 cell line was used to determine the direct effects of nicotine on trophoblast differentiation. Our in vivo experiments show that nicotine inhibits trophoblast interstitial invasion, increases placental hypoxia, downregulates labyrinth vascularization as well as key transcription factors Hand1 and GCM1, and decreases local and circulating EG-VEGF, a key placental angiogenic factor. The in vitro experiments confirmed the inhibitory effects of nicotine on the trophoblast migration, invasion, and differentiation processes and demonstrated that those effects are most likely due to a dysregulation in the expression of nicotine receptors and a decrease in MMP9 activity. Taken together, these data suggest that adverse effects of maternal smoking on pregnancy outcome are due in part to direct and endocrine effects of nicotine on the main processes of placental development and establishment of FC.

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.

Somatic donor cell type correlates with embryonic, but not extra-embryonic, gene expression in postimplantation cloned embryos

The great majority of embryos generated by somatic cell nuclear transfer (SCNT) display defined abnormal phenotypes after implantation, such as an increased likelihood of death and abnormal placentation. To gain better insight into the underlying mechanisms, we analyzed genome-wide gene expression profiles of day 6.5 postimplantation mouse embryos cloned from three different cell types (cumulus cells, neonatal Sertoli cells and fibroblasts). The embryos retrieved from the uteri were separated into embryonic (epiblast) and extraembryonic (extraembryonic ectoderm and ectoplacental cone) tissues and were subjected to gene microarray analysis. Genotype- and sex-matched embryos produced by in vitro fertilization were used as controls. Principal component analysis revealed that whereas the gene expression patterns in the embryonic tissues varied according to the donor cell type, those in extraembryonic tissues were relatively consistent across all groups. Within each group, the embryonic tissues had more differentially expressed genes (DEGs) (>2-fold vs. controls) than did the extraembryonic tissues (P<1.0×10^–26). In the embryonic tissues, one of the common abnormalities was upregulation of Dlk1, a paternally imprinted gene. This might be a potential cause of the occasional placenta-only conceptuses seen in SCNT-generated mouse embryos (1–5% per embryos transferred in our laboratory), because dysregulation of the same gene is known to cause developmental failure of embryos derived from induced pluripotent stem cells. There were also some DEGs in the extraembryonic tissues, which might explain the poor development of SCNT-derived placentas at early stages. These findings suggest that SCNT affects the embryonic and extraembryonic development differentially and might cause further deterioration in the embryonic lineage in a donor cell-specific manner. This could explain donor cell-dependent variations in cloning efficiency using SCNT.

CDX2 regulates multiple trophoblast genes in bovine trophectoderm CT-1 cells

The bovine trophectoderm (TE) undergoes a dramatic morphogenetic transition prior to uterine endometrial attachment. Many studies have documented trophoblast-specific gene expression profiles at various pre-attachment stages, yet genetic interactions within the transitioning TE gene regulatory network are not well characterized. During bovine embryogenesis, transcription factors OCT4 and CDX2 are co-expressed during early trophoblast elongation. In this study, the bovine trophectoderm-derived CT-1 cell line was utilized as a genetic model to examine the roles of CDX2 and OCT4 within the bovine trophoblast gene regulatory network. An RT-PCR screen for TE-lineage transcription factors identified expression of CDX2, ERRB, ID2, SOX15, ELF5, HAND1, and ASCL2. CT-1 cells also express a nuclear-localized, 360 amino acid OCT4 ortholog of the pluripotency-specific human OCT4A. To delineate the roles of CDX2 and OCT4 within the CT-1 gene network, CDX2 and OCT4 levels were manipulated via overexpression and siRNA-mediated knockdown. An increase in CDX2 negatively regulated OCT4 expression, but increased expression of IFNT, HAND1, ASCL2, SOX15, and ELF5. A reduction of CDX2 levels exhibited a reciprocal effect, resulting in decreased expression of IFNT, HAND1, ASCL2, and SOX15. Both overexpression and knockdown of CDX2 increased ETS2 transcription. In contrast to CDX2, manipulation of OCT4 levels only revealed a positive autoregulatory mechanism and upregulation of ASCL2. Together, these results suggest that CDX2 is a core regulator of multiple trophoblast genes within CT-1 cells.

The transcriptional co-repressor TLE3 regulates development of trophoblast giant cells lining maternal blood spaces in the mouse placenta

TLE3 is a transcriptional co-repressor that interacts with several DNA-binding repressors, including downstream effectors of the Notch signaling pathway. We generated Tle3-deficient mice and found that they die in utero and their death is associated with abnormal development of the placenta with major defects in the maternal vasculature. In the normal placenta, maternal blood spaces are lined, not as usual in the mammalian circulation by endothelial cells, but rather by specialized embryo-derived cells of the trophoblast cell lineage named trophoblast giant cells (TGC). Tle3 mRNA is expressed in those specialized TGC and Tle3 mutants show severe defects in differentiation of TGC-lined channels and lacunar spaces that take blood out of the labyrinth zone of the placenta and into the uterine veins. The mutants also show somewhat milder defects on the arterial-side of the maternal vascular circuit in spiral arteries and canals that take blood into the labyrinth. Notch2 and Tle3 expression patterns overlap in several TGC subtypes and we found that Tle3 and Notch2 mutants have some overlapping features. However, they also show differences implying that TLE3 may mediate some but not all of the effects of Notch2 signaling during placenta development. Therefore, formation of the different types of maternal blood spaces by different TGC subtypes is regulated by distinct molecular mechanisms.

The basic helix-loop-helix transcription factor Hand1 regulates mouse development as a homodimer

Hand1 is a basic helix-loop-helix transcription factor that is essential for development of the placenta, yolk sac and heart during mouse development. While Hand1 is essential for trophoblast giant cell (TGC) differentiation, its potential heterodimer partners are not co-expressed in TGCs. To test the hypothesis that Hand1 functions as homodimer, we generated knock-in mice in which the Hand1 gene was altered to encode a tethered homodimer (TH). Some Hand1(TH/-) conceptuses in which the only form of Hand1 is Hand1(TH) are viable and fertile, indicating that homodimer Hand1 is sufficient for mouse survival. ~2/3 of Hand1(TH/-) and all Hand1(TH/TH) mice died in utero and displayed severe placental defects and variable cardial and cranial-facial abnormalities, indicating a dosage-dependent effect of Hand1(TH). Meanwhile, expression of the Hand1(TH) protein did not have negative effects on viability or fertility in all Hand1(TH/+) mice. These data imply that Hand1 homodimer plays a dominant role during development and its expression dosage is critical for survival, whereas Hand1 heterodimers can be either dispensable or play a regulatory role to modulate the activity of Hand1 homodimer in vivo.

Regulation of murine placentogenesis by the retroviral genes Syncytin-A, Syncytin-B and Peg10

The murine placenta has a trichorial structure with two multinucleated syncytiotrophoblast (SCT) layers representing a barrier between the maternal and fetal blood system. Genes of endogenous retroviruses and retrotransposon-derived paternally expressed genes (Peg), remnants of past infections and integrations in the genome, have essential functions in placentogenesis. Previous studies showed that the envelope genes Syncytin-A and Syncytin-B were essential for cell-cell fusion of the SCT. The goal of this study was to analyze the temporal localization and expression of nine genes throughout placental development from embryonic day (E)8.5 to E18.5 using in situ-hybridization and absolute RNA-quantification. These included a comparison of previously characterized genes from the labyrinth Syncytin-A, Syncytin-B, Gcm1, the junctional zone PL-1, PL-2, Plf, Tpbpa with two further characterized genes Peg10 and Tpbpb. Syncytin-A and Syncytin-B RNA localized to SCT-I and SCT-II, respectively. Peg10 RNA localized to all extraembryonic tissues, specifically to the parietal and sinusoidal TGC of the labyrinth layer, which is in contact with SCT-I and the maternal blood. All three retroviral/retrotransposon-derived genes showed the highest expression at E16.5, but Peg10 with 188,917.1 molecules/ng cDNA was 208-fold and 106.8-fold higher expressed than Syncytin-A and Syncytin-B, respectively. Tpbpb localized to the junctional zone and showed the highest expression at E16.5 along with PL-2, Plf, Tpbpa, but not PL-1, which decreased in expression at E10.5. To investigate a role of Syncytin-A, Syncytin-B and Peg10 in cell-cell fusion, we established a cell culture system with fractionated primary trophoblasts from murine placentae. Culturing trophoblasts for up to 72h partly resembled trophoblast development in vivo according to the nine marker genes. Knockdown of Syncytin-A demonstrated a functional regulation of cell-cell fusion, where knockdown of Peg10 showed no involvement in cell fusion. Due to the expression of Peg10 in TGCs, we propose an essential functional role in the fetal-maternal blood system.

Possible regulatory roles of promoter g-quadruplexes in cardiac function-related genes - human TnIc as a model

G-quadruplexes (G4s) are four-stranded DNA secondary structures, which are involved in a diverse range of biological processes. Although the anti-cancer potential of G4s in oncogene promoters has been thoroughly investigated, the functions of promoter G4s in non-cancer-related genes are not well understood. We have explored the possible regulatory roles of promoter G4s in cardiac function-related genes using both computational and a wide range of experimental approaches. According to our bioinformatics results, it was found that potential G4-forming sequences are particularly enriched in the transcription regulatory regions (TRRs) of cardiac function-related genes. Subsequently, the promoter of human cardiac troponin I (TnIc) was chosen as a model, and G4s found in this region were subjected to biophysical characterisations. The chromosome 19 specific minisatellite G4 sequence (MNSG4) and near transcription start site (TSS) G4 sequence (−80 G4) adopt anti-parallel and parallel structures respectively in 100 mM KCl, with stabilities comparable to those of oncogene G4s. It was also found that TnIc G4s act cooperatively as enhancers in gene expression regulation in HEK293 cells, when stabilised by a synthetic G4-binding ligand. This study provides the first evidence of the biological significance of promoter G4s in cardiac function-related genes. The feasibility of using a single ligand to target multiple G4s in a particular gene has also been discussed.

Blimp1/Prdm1 governs terminal differentiation of endovascular trophoblast giant cells and defines multipotent progenitors in the developing placenta

Developmental arrest of Blimp1/Prdm1 mutant embryos at around embryonic day 10.5 (E10.5) has been attributed to placental disturbances. Here we investigate Blimp1/Prdm1 requirements in the trophoblast cell lineage. Loss of function disrupts specification of the invasive spiral artery-associated trophoblast giant cells (SpA-TGCs) surrounding maternal blood vessels and severely compromises the ability of the spongiotrophoblast layer to expand appropriately, secondarily causing collapse of the underlying labyrinth layer. Additionally, we identify a population of proliferating Blimp1(+) diploid cells present within the spongiotrophoblast layer. Lineage tracing experiments exploiting a novel Prdm1.Cre-LacZ allele demonstrate that these Blimp1(+) cells give rise to the mature SpA-TGCs, canal TGCs, and glycogen trophoblasts. In sum, the transcriptional repressor Blimp1/Prdm1 is required for terminal differentiation of SpA-TGCs and defines a lineage-restricted progenitor cell population contributing to placental growth and morphogenesis.

The maternally expressed gene Tssc3 regulates the expression of MASH2 transcription factor in mouse trophoblast stem cells through the AKT-Sp1 signaling pathway

Tssc3 is a maternally expressed/paternally silenced imprinted gene. Recent evidence suggests that the loss of TSSC3 results in placental overgrowth in mice. These findings showed that the TSSC3 gene functions as a negative regulator of placental growth. In this study, we describe the function of TSSC3 and its signaling pathway in mouse trophoblast stem (TS) cell differentiation. First of all, we tested Tssc3 expression levels in TS cells. TS cells expressed Tssc3, and its expression level was the highest from day 1 to 4 but was down-regulated at day 5 after the induction of differentiation. Overexpression of TSSC3 in TS cells up-regulated Gcm1 and Mash2, which are marker genes of mouse trophoblast differentiation. Down-regulation of TSSC3 by siRNA enhanced Pl1 and Tpbpa expression in TS cells cultured under stem cell conditions, suggesting the contribution of TSSC3 to the differentiation from TS to trophoblast progenitors and/or labyrinth trophoblasts. TSSC3 activated the PI3K/AKT pathway through binding with phosphatidylinositol phosphate lipids and enhanced the activity of a promoter containing an E-box structure, which is the binding sequence of the Mash2 downstream target gene promoter. PI3K inhibitor suppressed the promoter activity induced by TSSC3. TSSC3 induced Sp1 translocation from cytoplasm to nucleus through the PI3K/AKT pathway. Nuclear Sp1 activated the Mash2 transcription by Sp1 binding with a consensus Sp1-binding motif. This is the first report describing that TSSC3 plays an important role in the differentiation from TS to trophoblast progenitors and/or labyrinth trophoblasts through the TSSC3/PI3K/AKT/MASH2 signaling pathway.

Trophoblast development

This review summarises current knowledge about the specification, commitment and maintenance of the trophoblast lineage in mice and cattle. Results from gene expression studies, in vivo loss-of-function models and in vitro systems using trophoblast and embryonic stem cells have been assimilated into a model seeking to explain trophoblast ontogeny via gene regulatory networks. While trophoblast differentiation is quite distinct between cattle and mice, as would be expected from their different modes of implantation, recent studies have demonstrated that differences arise much earlier during trophoblast development.

Forkhead factor FoxO1 is essential for placental morphogenesis in the developing embryo

Forkhead box O1 (FoxO1), a member of the Forkhead box-containing O family of transcription factors, is a key regulator of numerous genes that govern a wide array of cellular functions, including differentiation, homeostasis, and survival. However, the role of FoxO1 in development remains elusive. Here, we describe an essential and previously undefined role for FoxO1 in placental development. We demonstrate that FoxO1-null embryos up to embryonic day 9.0 (E9.0) are indistinguishable, including their morphology, cardiovascular structure, and vascular gene expression, from wild-type (WT) littermates. However, FoxO1-nulls manifested a profoundly swollen/hydropic allantois, which failed to fuse with the chorion, a phenotype that leads to subsequent cardiovascular malformation, progressive apoptotic cell death, and embryonic lethality at E10.5. Quantitative RT-PCR analysis of genes involved in placental development revealed significant attenuation of VCAM1 expression in FoxO1-null embryos. Using immunohistochemical, transcriptional, and chromatin immunoprecipitation assays, we further discovered that FoxO1 is an essential upstream regulator of the VCAM1 gene. Collectively, our findings provide critical molecular insight into a unique FoxO1-VCAM1 axis that governs placental morphogenesis, a process that is essential for subsequent normal cardiovascular development and fetal life.

Transcriptional responses of cultured rat sympathetic neurons during BMP-7-induced dendritic growth

BACKGROUND

Dendrites are the primary site of synapse formation in the vertebrate nervous system; however, relatively little is known about the molecular mechanisms that regulate the initial formation of primary dendrites. Embryonic rat sympathetic neurons cultured under defined conditions extend a single functional axon, but fail to form dendrites. Addition of bone morphogenetic proteins (BMPs) triggers these neurons to extend multiple dendrites without altering axonal growth or cell survival. We used this culture system to examine differential gene expression patterns in naïve vs. BMP-treated sympathetic neurons in order to identify candidate genes involved in regulation of primary dendritogenesis.

METHODOLOGY/PRINCIPAL FINDINGS

To determine the critical transcriptional window during BMP-induced dendritic growth, morphometric analysis of microtubule-associated protein (MAP-2)-immunopositive processes was used to quantify dendritic growth in cultures exposed to the transcription inhibitor actinomycin-D added at varying times after addition of BMP-7. BMP-7-induced dendritic growth was blocked when transcription was inhibited within the first 24 hr after adding exogenous BMP-7. Thus, total RNA was isolated from sympathetic neurons exposed to three different experimental conditions: (1) no BMP-7 treatment; (2) treatment with BMP-7 for 6 hr; and (3) treatment with BMP-7 for 24 hr. Affymetrix oligonucleotide microarrays were used to identify differential gene expression under these three culture conditions. BMP-7 significantly regulated 56 unique genes at 6 hr and 185 unique genes at 24 hr. Bioinformatic analyses implicate both established and novel genes and signaling pathways in primary dendritogenesis.

CONCLUSIONS/SIGNIFICANCE

This study provides a unique dataset that will be useful in generating testable hypotheses regarding transcriptional control of the initial stages of dendritic growth. Since BMPs selectively promote dendritic growth in central neurons as well, these findings may be generally applicable to dendritic growth in other neuronal cell types.

L3MBTL1 deficiency directs the differentiation of human embryonic stem cells toward trophectoderm

Human embryonic stem cells (hESCs) can be used to study the early events in human development and, hopefully, to understand how to differentiate human pluripotent cells for clinical use. To define how L3MBTL1, a chromatin-associated polycomb group protein with transcriptional repressive activities, regulates early events in embryonic cell differentiation, we created hESC lines that constitutively express shRNAs directed against L3MBTL1. The L3MBTL1 knockdown (KD) hESCs maintained normal morphology, proliferation, cell cycle kinetics, cell surface markers, and karyotype after 40 passages. However, under conditions that promote spontaneous differentiation, the L3MBTL1 KD cells differentiated into a relatively homogeneous population of large, flat trophoblast-like cells, unlike the multilineage differentiation seen with the control cells. The differentiated L3MBTL1 KD cells expressed numerous trophoblast markers and secreted placental hormones. Although the L3MBTL1 KD cells could be induced to differentiate into various embryonic lineages, they adopted an exclusive trophoblast fate during spontaneous differentiation. Our data demonstrate that depletion of L3MBTL1 does not affect hESC self-renewal, rather it enhances differentiation toward extra-embryonic trophoblast tissues.

G-quadruplexes-novel mediators of gene function

Since the famous double-helix model was proposed, chromosomal DNA has been regarded as a rigid molecule containing the genetic information of an organism. It is clear now that DNA can adopt many transient, complex structures that can perform different biological functions. The G4 DNA (also called DNA G-quadruplex or G-tetraplex), a four-stranded DNA structure composed of stacked G-tetrads (guanine tetrads), has attracted much attention during the past two decades due to its ability to adopt a variety of structures and its possible biological functions. This review gives a glimpse on the structural diversity and biophysical properties of these fascinating DNA structures. Common methods that are widely used in investigating biophysical properties and biological functions of G4 DNA are described briefly. Next, bioinformatics studies that indicate evidence of evolutionary selection and potential functions of G4 DNA are discussed. Finally, examples of various biological functions of different G4 DNA are given, and potential roles of G4 DNA in respect of cardiovascular science are discussed.

The mouse KRAB zinc-finger protein CHATO is required in embryonic-derived tissues to control yolk sac and placenta morphogenesis

Yolk sac and placenta are required to sustain embryonic development in mammals, yet our understanding of the genes and processes that control morphogenesis of these extraembryonic tissues is still limited. The chato mutation disrupts ZFP568, a Krüppel-Associated-Box (KRAB) domain Zinc finger protein, and causes a unique set of extraembryonic malformations, including ruffling of the yolk sac membrane, defective extraembryonic mesoderm morphogenesis and vasculogenesis, failure to close the ectoplacental cavity, and incomplete placental development. Phenotypic analysis of chato embryos indicated that ZFP568 does not control proliferation or differentiation of extraembryonic lineages but rather regulates the morphogenetic events that shape extraembryonic tissues. Analysis of chimeric embryos showed that Zfp568 function is required in embryonic-derived lineages, including the extraembryonic mesoderm. Depleting Zfp568 affects the ability of extraembryonic mesoderm cells to migrate. However, explanted Zfp568 mutant cells could migrate properly when plated on appropriate extracellular matrix conditions. We show that expression of Fibronectin and Indian Hedgehog are reduced in chato mutant yolk sacs. These data suggest that ZFP568 controls the production of secreted factors required to promote morphogenesis of extraembryonic tissues. Our results support previously undescribed roles of the extraembryonic mesoderm in yolk sac morphogenesis and in the closure of the ectoplacental cavity and identify a novel role of ZFP568 in the development of extraembryonic tissues.

Endocannabinoid signaling directs differentiation of trophoblast cell lineages and placentation

In most mammals, placentation is critical for fetal development and pregnancy success. Exposure to marijuana during pregnancy has adverse effects, but whether the placenta is a target of cannabinoid/endocannabinoid signaling is not known. Using mice as a model system, we found that the endocannabinoid system is present in the ectoplacental cone and spongiotrophoblast cells. We also observed that aberrant endocannabinoid signaling confers premature trophoblast stem cell differentiation, and defective trophoblast development and invasion. These defects are reflected in retarded fetal development and compromised pregnancy outcome. Because the endocannabinoid system is conserved in mice and humans, our study suggests that endocannabinoid signaling is critical to placentation and pregnancy success in humans and implicates its potential significance in stem cell biology.

A genomic imprinting defect in mice traced to a single gene

Mammalian androgenones have two paternally or sperm-derived genomes. In mice (Mus musculus) they die at peri-implantation due to the misexpression of imprinted genes-the genes that are expressed monoallelically according to the parent of origin. The misexpressions involved are poorly defined. To gain further insight, we examined the causes of midgestation death of embryos with paternal duplication (PatDp) of distal chromosome 7 (dist7), a region replete with imprinted genes. PatDp(dist7) embryos have a similar phenotype to mice with a knockout of a maternally expressed imprinted gene, Ascl2 [achaete-scute complex homolog-like 2 (Drosophila)], and their death at midgestation could result from two inactive paternal copies of this gene. However, other dist7 misexpressions could duplicate this phenotype, and the potential epistatic load is undefined. We show that an Ascl2 transgene is able to promote the development of PatDp(dist7) embryos to term, providing strong evidence that Ascl2 is the only imprinted gene in the genome for which PatDp results in early embryonic death. While some of the defects in perinatal transgenic PatDp(dist7) fetuses were consistent with known misexpressions of dist7 imprinted genes, the overall phenotype indicates a role for additional undefined misexpressions of imprinted genes. This study provides implications for the human imprinting-related fetal overgrowth disorder, Beckwith-Wiedemann syndrome.

The placenta: transcriptional, epigenetic, and physiological integration during development

The placenta provides critical transport functions between the maternal and fetal circulations during intrauterine development. Formation of this interface relies on coordinated interactions among transcriptional, epigenetic, and environmental factors. Here we describe these mechanisms in the context of the differentiation of placental cells (trophoblasts) and synthesize current knowledge about how they interact to generate a functional placenta. Developing an understanding of these pathways contributes to an improvement of our models for studying trophoblast biology and sheds light on the etiology of pregnancy complications and the in utero programming of adult diseases.

Stk40 links the pluripotency factor Oct4 to the Erk/MAPK pathway and controls extraembryonic endoderm differentiation

Self-renewal and differentiation of embryonic stem cells (ESCs) are controlled by intracellular transcriptional factors and extracellular factor-activated signaling pathways. Transcription factor Oct4 is a key player maintaining ESCs in an undifferentiated state, whereas the Erk/MAPK pathway is known to be important for ESC differentiation. However, the manner in which intracellular pluripotency factors modulate extracellular factor-activated signaling pathways in ESCs is not well understood. Here, we report identification of a target gene of Oct4, serine/threonine kinase 40 (Stk40), which is able to activate the Erk/MAPK pathway and induce extraembryonic-endoderm (ExEn) differentiation in mouse ESCs. Interestingly, cells overexpressing Stk40 exclusively contribute to the ExEn layer of chimeric embryos when injected into host blastocysts. In contrast, deletion of Stk40 in ESCs markedly reduces ExEn differentiation in vitro. Mechanistically, Stk40 interacts with Rcn2, which also activates Erk1/2 to induce ExEn specification in mouse ESCs. Moreover, Rcn2 proteins are specifically located in the cytoplasm of the ExEn layer of early mouse embryos. Importantly, knockdown of Rcn2 blocks Stk40-activated Erk1/2 and ESC differentiation. Therefore, our study establishes a link between the pluripotency factor Oct4 and the Erk/MAPK signaling pathway, and it uncovers cooperating signals in the Erk/MAPK activation that control ExEn differentiation.

Genes and signals regulating murine trophoblast cell development

A fundamental step in embryonic development is cell differentiation whereby highly specialised cell types are developed from a single undifferentiated, fertilised egg. One of the earliest lineages to form in the mammalian conceptus is the trophoblast, which contributes exclusively to the extraembryonic structures that form the placenta. Trophoblast giant cells (TGCs) in the rodent placenta form the outermost layer of the extraembryonic compartment, establish direct contact with maternal cells, and produce a number of pregnancy-specific cytokine hormones. Giant cells differentiate from proliferative trophoblasts as they exit the cell cycle and enter a genome-amplifying endocycle. Normal differentiation of secondary TGCs is a critical step toward the formation of the placenta and normal embryonic development. Trophoblast development is also of particular interest to the developmental biologist and immunobiologist, as these cells constitute the immediate cellular boundary between the embryonic and maternal tissues. Abnormalities in the development of secondary TGCs results in severe malfunction of the placenta. Herein we review new information that has been accumulated recently regarding the molecular and cellular regulation of trophoblast and placenta development. In particular, we discuss the molecular aspects of murine TGC differentiation. We also focus on the role of growth and transcription factors in TGC development.