Life Sciences Research for Lifelong Health

Publications myriam-hemberger

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Stem cells from fetal membranes - a workshop report.
Hemberger M, Yang W, Natale D, Brown TL, Dunk C, Gargett CE, Tanaka S

Stem cells that can be derived from fetal membranes represent an exciting field of research that bears tremendous potential for developmental biology and regenerative medicine. In this report we summarize contributions to a workshop in which newest insights into the characteristics, subtypes and molecular determinants of stem cells from trophoblast and endometrial tissues were presented.

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Placenta, 29 Suppl A, 0143-4004, S17-9, 2008

PMID: 18155293

IFPA award in placentology lecture - characteristics and significance of trophoblast giant cells.
M Hemberger

Extraembryonic development in rodents depends on the differentiation and function of trophoblast giant cells. Morphologically striking, giant cells exhibit many extraordinary characteristics adapted to ensure the success of pregnancy. This review summarizes some of the intriguing aspects of giant cell morphology and function. Giant cells are highly polyploid as a result of a switch from a mitotic to an endoreduplicative cell cycle. They further partition their genome content into various fragments which may represent a mechanism to maximize protein synthesis. Similar to metastatic tumour cells, they breach basement membranes and invade deeply into a foreign tissue, the maternal decidualized uterine stroma. Their angiogenic and vasodilatory properties, combined with the ability to remodel arterial walls, enable them to redirect maternal blood flow towards the implantation site. Recent advances have recognized that the giant cell population is more diverse than previously recognized and future studies will have to show how these subtypes differ functionally and how their differentiation is controlled.

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Placenta, 29 Suppl A, , S4-9, 2008

PMID: 18083226
DOI: 10.1016/j.placenta.2007.11.007

Epigenetic landscape required for placental development.
M Hemberger

Formation of extraembryonic tissues, and in particular the placenta, is an absolute necessity to ensure growth and survival of the embryo during intrauterine development in mammals. To date, an intriguing number of genes have been identified that are essential for development of extraembryonic structures. However, the underlying genetic information must be interpreted by a set of epigenetic instructions to both establish and maintain lineage- and cell type-specific expression profiles. Based on accumulating data in particular from studies in the mouse, this article is aimed at highlighting the epigenetic machinery required for differentiation of extraembryonic cell types and formation of the placenta. An overview of knockout models reveals key stages in extraembryonic development that are particularly sensitive to alterations in the chromatin environment. The article also summarizes the importance of complex epigenetically controlled mechanisms for placental development, such as imprinted gene expression and imprinted X chromosome inactivation. These investigations of the epigenetic regulation of transcriptional states will provide valuable insights into the dynamic chromatin environment that is specific to extraembryonic tissues and determines gene expression patterns required for normal trophoblast differentiation.

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Cellular and molecular life sciences : CMLS, 64, 18, 2422-36, 2007

PMID: 17585370
DOI: 10.1007/s00018-007-7113-z

Epigenetic arbitration of cell fate decisions: tipping the bias.
M Hemberger, W Dean

Epigenetic modifications of nucleosomal histones are thought to mediate transcriptional states and impose heritable instructions upon differentiation. In a paper of Torres-Padilla and colleagues in Nature, protein modification at arginine residues, namely of core histones, is correlated with cell fate determination at the 4-cell stage in the mouse embryo. This represents the first link of global epigenetic instructions associated with specification of early cell lineages.

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Developmental cell, 12, 2, 176-8, 2007

PMID: 17276335
DOI: 10.1016/j.devcel.2006.12.004

Open Access

Improved endothelial function and reduced platelet activation by chronic HMG-CoA-reductase inhibition with rosuvastatin in rats with streptozotocin-induced diabetes mellitus.
Schäfer A, Fraccarollo D, Vogt C, Flierl U, Hemberger M, Tas P, Ertl G, Bauersachs J

Diabetes is associated with endothelial dysfunction and platelet activation, both of which may contribute to increased cardiovascular risk. We investigated whether the hydroxy-3-methyl-glutaryl CoA reductase inhibitor rosuvastatin improves endothelial function and reduces platelet activation in diabetic rats. Therefore, male Wistar rats were injected with streptozotocin (STZ, 50mg/kg i.v.) to induce insulin-deficient diabetes. Treatment with rosuvastatin (20mg/[kg day]) or vehicle was initiated 2 weeks after injection of STZ and continued for 2 weeks. Thereafter, platelet activation was assessed in fresh whole blood and vascular function was characterized in isolated aortic segments in organ bath chambers. Endothelium-dependent relaxation induced by acetylcholine was significantly attenuated in diabetic rats and improved by treatment with rosuvastatin (maximum relaxation, % of precontraction-control: 99.8+/-0.2, STZ-vehicle: 80.7+/-2.9, STZ-rosuvastatin: 98.9+/-0.7; p

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Biochemical pharmacology, 73, 0006-2952, 1367-75, 2007

PMID: 17270148

Improved endothelial function and reduced platelet activation by chronic HMG-CoA-reductase inhibition with rosuvastatin in rats with streptozotocin-induced diabetes mellitus.
Schäfer A, Fraccarollo D, Vogt C, Flierl U, Hemberger M, Tas P, Ertl G, Bauersachs J

Diabetes is associated with endothelial dysfunction and platelet activation, both of which may contribute to increased cardiovascular risk. We investigated whether the hydroxy-3-methyl-glutaryl CoA reductase inhibitor rosuvastatin improves endothelial function and reduces platelet activation in diabetic rats. Therefore, male Wistar rats were injected with streptozotocin (STZ, 50mg/kg i.v.) to induce insulin-deficient diabetes. Treatment with rosuvastatin (20mg/[kg day]) or vehicle was initiated 2 weeks after injection of STZ and continued for 2 weeks. Thereafter, platelet activation was assessed in fresh whole blood and vascular function was characterized in isolated aortic segments in organ bath chambers. Endothelium-dependent relaxation induced by acetylcholine was significantly attenuated in diabetic rats and improved by treatment with rosuvastatin (maximum relaxation, % of precontraction-control: 99.8+/-0.2, STZ-vehicle: 80.7+/-2.9, STZ-rosuvastatin: 98.9+/-0.7; p

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Biochemical pharmacology, 73, 0006-2952, 1367-75, 2007

PMID: 17270148

Carboxypeptidase E in the mouse placenta.
Singh U, Yu Y, Kalinina E, Konno T, Sun T, Ohta H, Wakayama T, Soares MJ, Hemberger M, Fundele RH

Carboxypeptidase E (CPE) has important functions in processing of endocrine pro-peptides, such as pro-insulin, pro-opiomelanocortin, or pro-gonadotropin-releasing hormone, as evidenced by the hyper-pro-insulinemia, obesity, and sterility of Cpe mutant mice. Down-regulation of Cpe in enlarged placentas of interspecific hybrid (interspecies hybrid placental dysplasia (IHPD)) and cloned mice suggested that reduced CPE enzyme and receptor activity could underlie abnormal placental phenotypes. In this study, we have explored the role of Cpe in murine placentation by determining its expression at various stages of gestation, and by phenotypic analysis of Cpe mutant placentas. Our results show that Cpe and Carboxypeptidase D (Cpd), another carboxypeptidase with a very similar function, are strictly co-localized in the mouse placenta from late mid-gestation to term. We also show that absence of CPE causes a sporadic but striking placental phenotype characterized by an increase in giant and glycogen cell numbers and giant cell hypertrophy. Microarray-based transcriptional profiling of Cpe mutant placentas identified only a very small number of genes with altered expression, including Dtprp, which belongs to the prolactin gene family. Concordant deregulation of Cpe and Cpd in abnormal placentas of interspecies hybrids before the onset of IHPD phenotype and recapitulation of some phenotypes of IHPD hyperplastic placentas in Cpe mutant placentas suggests that these two genes are causally involved in IHPD and may function as speciation genes in the genus Mus.

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Differentiation; research in biological diversity, 74, 0301-4681, 648-60, 2006

PMID: 17177860

Epigenetic dynamics of the Kcnq1 imprinted domain in the early embryo.
Lewis A, Green K, Dawson C, Redrup L, Huynh KD, Lee JT, Hemberger M, Reik W

The mouse Kcnq1 imprinted domain is located on distal chromosome 7 and contains several imprinted genes that are paternally repressed. Repression of these genes is regulated by a non-coding antisense transcript, Kcnq1ot1, which is paternally expressed. Maternal repression of Kcnq1ot1 is controlled by DNA methylation originating in the oocyte. Some genes in the region are imprinted only in the placenta, whereas others are imprinted in both extra-embryonic and embryonic lineages. Here, we show that Kcnq1ot1 is paternally expressed in preimplantation embryos from the two-cell stage, and that ubiquitously imprinted genes proximal to Kcnq1ot1 are already repressed in blastocysts, ES cells and TS cells. Repressive histone marks such as H3K27me3 are present on the paternal allele of these genes in both ES and TS cells. Placentally imprinted genes that are distal to Kcnq1ot1, by contrast, are not imprinted in blastocysts, ES or TS cells. In these genes, paternal silencing and differential histone marks arise during differentiation of the trophoblast lineage between E4.5 and E7.5. Our findings show that the dynamics during preimplantation development of gene inactivation and acquisition of repressive histone marks in ubiquitously imprinted genes of the Kcnq1 domain are very similar to those of imprinted X inactivation. By contrast, genes that are only imprinted in the placenta, while regulated by the same non-coding RNA transcript Kcnq1ot1, undergo epigenetic inactivation during differentiation of the trophoblast lineage. Our findings establish a model for how epigenetic gene silencing by non-coding RNA may depend on distance from the non-coding RNA and on lineage and differentiation specific factors.

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Development (Cambridge, England), 133, 0950-1991, 4203-10, 2006

PMID: 17021040

Open Access

Geminin is essential to prevent endoreduplication and to form pluripotent cells during mammalian development.
Gonzalez MA, Tachibana KE, Adams DJ, van der Weyden L, Hemberger M, Coleman N, Bradley A, Laskey RA

In multicellular eukaryotes, geminin prevents overreplication of DNA in proliferating cells. Here, we show that genetic ablation of geminin in the mouse prevents formation of inner cell mass (ICM) and causes premature endoreduplication at eight cells, rather than 32 cells. All cells in geminin-deficient embryos commit to the trophoblast cell lineage and consist of trophoblast giant cells (TGCs) only. Geminin is also down-regulated in TGCs of wild-type blastocysts during S and gap-like phases by proteasome-mediated degradation, suggesting that loss of geminin is part of the mechanism regulating endoreduplication.

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Genes & development, 20, 0890-9369, 1880-4, 2006

PMID: 16847348

Open Access

The importance of cysteine cathepsin proteases for placental development.
A Varanou, SL Withington, L Lakasing, C Williamson, GJ Burton, M Hemberger

The typically lysosomal family of cysteine cathepsin proteases has been implicated in the development of the placenta in particular, from studies in the mouse. Here, we analysed overall expression, regulation and presence of transcript isoforms of cysteine cathepsins during human extra-embryonic development. All 11 family members are expressed in human placental tissues, and many are differentially regulated during gestation. Several cysteine cathepsins exhibit deregulated expression levels in placentas from pregnancies complicated by pre-eclampsia. The localization of cathepsin B predominantly in placental and decidual macrophages suggests a role in the physiological functions of these cells in mediating villous angiogenesis and decidual apoptosis. Cathepsin L levels are highest in a subpopulation of invasive cytotrophoblasts. Reflecting the expression pattern of two murine cathepsins, these data give insights into the evolutionary conservation of cathepsin function that is not necessarily exhibited by gene pairs defined by highest sequence similarity. Furthermore, cathepsin L protein localization in uterine epithelial cells demonstrates the in vivo occurrence of intranuclear cathepsin L isoforms. The zonally restricted expression of cathepsin in the syncytiotrophoblast may be important for the metabolic breakdown of maternal nutrients. Overall, the distribution and abnormal expression levels in pre-eclamptic placentas indicate that cysteine cathepsins may play important roles during normal placentation and in the etiology of pre-eclampsia.

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Journal of molecular medicine (Berlin, Germany), 84, 4, 305-17, 2006

PMID: 16440214
DOI: 10.1007/s00109-005-0032-2

Expression and functional analysis of genes deregulated in mouse placental overgrowth models: Car2 and Ncam1.
Singh U, Sun T, Shi W, Schulz R, Nuber UA, Varanou A, Hemberger MC, Elliott RW, Ohta H, Wakayama T, Fundele R

Different causes, such as maternal diabetes, cloning by nuclear transfer, interspecific hybridization, and deletion of some genes such as Esx1, Ipl, or Cdkn1c, may underlie placental overgrowth. In a previous study, we carried out comparative gene expression analysis in three models of placental hyperplasias, cloning, interspecies hybridization (IHPD), and Esx1 deletion. This study identified a large number of genes that exhibited differential expression between normal and enlarged placentas; however, it remained unclear how altered expression of any specific gene was related to any specific placental phenotype. In the present study, we focused on two genes, Car2 and Ncam1, which both exhibited increased expression in interspecies and cloned hyperplastic placentas. Apart from a detailed expression analysis of both genes during normal murine placentation, we also assessed morphology of placentas that were null for Car2 or Ncam1. Finally, we attempted to rescue placental hyperplasia in a congenic model of IHPD by decreasing transcript levels of Car2 or Ncam1. In situ analysis showed that both genes are expressed mainly in the spongiotrophoblast, however, expression patterns exhibited significant variability during development. Contrary to expectations, homozygous deletion of either Car2 or Ncam1 did not result in placental phenotypes. However, expression analysis of Car3 and Ncam2, which can take over the function of Car2 and Ncam1, respectively, indicated a possible rescue mechanism, as Car3 and Ncam2 were expressed in spongiotrophoblast of Car2 and Ncam1 mutant placentas. On the other hand, downregulation of either Car2 or Ncam1 did not rescue any of the placental phenotypes of AT24 placentas, a congenic model for interspecies hybrid placentas. This strongly suggested that altered expression of Car2 and Ncam1 is a downstream event in placental hyperplasia.

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Developmental dynamics : an official publication of the American Association of Anatomists, 234, 1058-8388, 1034-45, 2005

PMID: 16247769

Open Access

Genetic and genomic approaches to study placental development.
Hemberger M, Zechner U

Recent technological advances in genetic manipulation and expression profiling offer excellent opportunities to elucidate the molecular mechanisms controlling developmental processes during embryogenesis. Thus, this revolution also strongly benefits studies of the molecular genetics of placental development. Here we review the findings of several expression profiling analyses in extraembryonic tissues and assess how this work can contribute to the identification of essential components governing placental development. We further discuss the relevance of these components in the context of genetic manipulation experiments. In conclusion, the intelligent combination of genetic and genomic approaches will substantially accelerate the progress in identifying the key molecular pathways of placental development.

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Cytogenetic and genome research, 105, 1424-859X, 257-69, 2004

PMID: 15237215

Trophoblast stem cells differentiate in vitro into invasive trophoblast giant cells.
Hemberger M, Hughes M, Cross JC

Trophoblast cells are characterized by an invasive behavior into the surrounding uterine tissue. In rodents, an early peri-/endovascular type of invasion exerted by trophoblast giant cells can be distinguished from a late interstitial type carried out by glycogen trophoblast cells. Analysis of the molecular mechanisms of trophoblast invasion has been hampered, however, by the complex temporal and spatial patterns of invasion. We utilized trophoblast stem (TS) cell lines to study trophoblast invasion in vitro and to establish a model that facilitates investigation of this process on the molecular level. Our results showed that trophoblast giant cells that differentiate from TS cells in vitro are capable of penetrating a reconstituted basement membrane matrix. Consequently, invasion rates were increased in various giant cell differentiation-promoting conditions. We also derived TS cell lines that are homozygous for a mutation of the Hand1 transcription factor. The Hand1-/- TS cells showed reduced levels of giant cell differentiation and exhibited an approximately 50% decrease in invasion rates. In summary, trophoblast giant cells that differentiate from TS cells in vitro recapitulate the invasive capacity of normal trophoblast cells in vivo. The TS cell system is a valuable tool to identify and quantitatively study regulators of trophoblast invasion.

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Developmental biology, 271, 0012-1606, 362-71, 2004

PMID: 15223340

Divergent genetic and epigenetic post-zygotic isolation mechanisms in Mus and Peromyscus.
Zechner U, Shi W, Hemberger M, Himmelbauer H, Otto S, Orth A, Kalscheuer V, Fischer U, Elango R, Reis A, Vogel W, Ropers H, Rüschendorf F, Fundele R

Interspecific hybridization in the rodent genera Peromyscus and Mus results in abnormal placentation. In the Peromyscus interspecies hybrids, abnormal allelic interaction between an X-linked locus and the imprinted paternally expressed Peg3 locus was shown to cause the placental defects. In addition, loss-of-imprinting (LOI) of Peg3 was positively correlated with increased placental size. As in extreme cases this placental dysplasia constitutes a post-zygotic barrier against interspecies hybridization, this finding was the first direct proof that imprinted genes may be important in speciation and thus in evolution. In the Mus interspecies hybrids, a strong role of an X-linked locus in placental dysplasia has also been detected. However, here we show by backcross and allele specific expression analyses that neither LOI of Peg3 nor abnormal interactions between Peg3 and an X-linked locus are involved in generating placental dysplasia in Mus hybrids, although the placental phenotypes observed in the two genera seem to be identical. In contrast to this, another dysgenesis effect common to Peromyscus and Mus hybrids, altered foetal growth, is caused at least in part by the same X-chromosomal regions in both genera. These findings first underline the strong involvement of the X-chromosome in the genetics of speciation. Secondly, they indicate that disruption of epigenetic states, such as LOI, at specific loci may be involved in hybrid dysgenesis effects in one group, but not in another. Thus, we conclude that even in closely related groups divergent molecular mechanisms may be involved in the production of phenotypically similar post-zygotic barriers against hybridization.

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Journal of evolutionary biology, 17, 1010-061X, 453-60, 2004

PMID: 15009278