scholarly journals MED20 is essential for early embryogenesis and regulates NANOG expression

Reproduction ◽  
2019 ◽  
Vol 157 (3) ◽  
pp. 215-222 ◽  
Author(s):  
Wei Cui ◽  
Chelsea Marcho ◽  
Yongsheng Wang ◽  
Rinat Degani ◽  
Morgane Golan ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Cell Lineage ◽  
Blastocyst Stage ◽  
Mediator Complex ◽  
Mammalian Development ◽  
Lineage Specification ◽  
Mammalian Embryo ◽  
Pol Ii

Mediator is an evolutionarily conserved multi-subunit complex, bridging transcriptional activators and repressors to the general RNA polymerase II (Pol II) initiation machinery. Though the Mediator complex is crucial for the transcription of almost all Pol II promoters in eukaryotic organisms, the phenotypes of individual Mediator subunit mutants are each distinct. Here, we report for the first time, the essential role of subunit MED20 in early mammalian embryo development. Although Med20 mutant mouse embryos exhibit normal morphology at E3.5 blastocyst stage, they cannot be recovered at early post-gastrulation stages. Outgrowth assays show that mutant blastocysts cannot hatch from the zona pellucida, indicating impaired blastocyst function. Assessments of cell death and cell lineage specification reveal that apoptosis, inner cell mass, trophectoderm and primitive endoderm markers are normal in mutant blastocysts. However, the epiblast marker NANOG is ectopically expressed in the trophectoderm of Med20 mutants, indicative of defects in trophoblast specification. These results suggest that MED20 specifically, and the Mediator complex in general, are essential for the earliest steps of mammalian development and cell lineage specification.

Embryo structure reorganisation reduces the probability of apoptosis in preimplantation mouse embryos

2021 ◽  
Vol 33 (12) ◽  
pp. 725
Author(s):  
Dawid Winiarczyk ◽  
Anna Piliszek ◽  
Silvestre Sampino ◽  
Marek Lukaszewicz ◽  
Jacek Andrzej Modliński
Keyword(s):  
Cell Volume ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Cell Lineage ◽  
Cell Number ◽  
Blastocyst Stage ◽  
Mammalian Development ◽  
Mouse Development ◽  
Preimplantation Mouse ◽  
Morula Stage

Programmed cell death plays a key role in mammalian development because the morphological events of an organism’s formation are dependent on apoptosis. In the mouse development, the first apoptotic waves occur physiologically at the blastocyst stage. Cell number and the mean nucleus to cytoplasm (N/C) ratio increase exponentially throughout subsequent embryo cleavages, while cell volume concurrently decreases from the zygote to blastocyst stage. In this study we tested the hypothesis that reorganisation of the embryo structure by manipulating cell number, the N/C ratio and the cell volume of 2-cell embryos may result in the earlier and more frequent occurrence of apoptosis. The results indicate that doubling (‘Aggregates’ group) or halving (‘Embryos 1/2’ group) the initial cell number and modifying embryo volume, ploidy (‘Embryos 4n’ group) and the N/C ratio (‘Embryos 2/1’ group) reduce the probability of apoptosis in the resulting embryos. There was a higher probability of apoptosis in the inner cell mass of the blastocyst, but apoptotic cells were never observed at the morula stage in any of the experimental groups. Thus, manipulation of cell number, embryo volume, the N/C ratio and ploidy cause subtle changes in the occurrence of apoptosis, although these are mostly dependent on embryo stage and cell lineage (trophectoderm or inner cell mass), which have the greatest effect on the probability of apoptosis.

Defects in the allocation of cells to the inner cell mass and trophectoderm of parthenogenetic mouse blastocysts

1996 ◽  
Vol 8 (8) ◽  
pp. 1193 ◽  
Author(s):  
B Mognetti ◽  
D Sakkas
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Substantial Reduction ◽  
Cell Lineage ◽  
Blastocyst Stage ◽  
Trophectoderm Cells ◽  
Parthenogenetic Development ◽  
Preimplantation Stage ◽  
Parthenogenetic Mouse Embryos ◽  
Parthenogenetic Embryos

Diploid parthenogenetic mouse embryos (which possess two maternally-derived genomes) can develop only as far as the 25-somite stage when transferred in utero and exhibit a substantial reduction in trophoblast tissue. The loss of cultured parthenogenetic embryos during postimplantation indicates that a defect in cell lineage may be evident as early as the blastocyst stage. The possibility that a defect may already be reflected at the preimplantation stage was investigated by examining the allocation of cells to the trophectoderm (trophoblast progenitor cells) and the inner cell mass of haploid and diploid parthenogenetic mouse blastocysts. Utilizing a differential labelling technique for counting cells, diploid parthenogenetic blastocysts were found to have fewer inner cell mass cells and trophectoderm cells than their haploid counterparts and normal blastocysts. In addition, both haploid and diploid parthenogenetic blastocysts had a lower inner cell mass: trophectoderm ratio than normal blastocysts. Thus, the relatively poor development of the trophectoderm lineage at the postimplantation stage is not reflected by a reduction in its allotment of cells at its first appearance. Nevertheless, the findings indicate that parthenogenetic development is already compromised at the blastocyst stage, and provide evidence that the expression of imprinted genes has significance for the development of the embryo at the preimplantation stage.

scholarly journals Epigenetic asymmetry in the mammalian zygote and early embryo: relationship to lineage commitment?

2003 ◽  
Vol 358 (1436) ◽  
pp. 1403-1409 ◽  
Author(s):  
Wolf Reik ◽  
Fatima Santos ◽  
Kohzoh Mitsuya ◽  
Hugh Morgan ◽  
Wendy Dean
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Blastocyst Stage ◽  
Early Embryo ◽  
Lineage Commitment ◽  
Imprinted Genes ◽  
Mammalian Development ◽  
Paternal Genome ◽  
Developmental Defects ◽  
Set Up

Epigenetic asymmetry between parental genomes and embryonic lineages exists at the earliest stages of mammalian development. The maternal genome in the zygote is highly methylated in both its DNA and its histones and most imprinted genes have maternal germline methylation imprints. The paternal genome is rapidly remodelled with protamine removal, addition of acetylated histones, and rapid demethylation of DNA before replication. A minority of imprinted genes have paternal germline methylation imprints. Methylation and chromatin reprogramming continues during cleavage divisions, but at the blastocyst stage lineage commitment to inner cell mass (ICM) or trophectoderm (TE) fate is accompanied by a dramatic increase in DNA and histone methylation, predominantly in the ICM. This may set up major epigenetic differences between embryonic and extraembryonic tissues, including in X–chromosome inactivation and perhaps imprinting. Maintaining epigenetic asymmetry appears important for development as asymmetry is lost in cloned embryos, most of which have developmental defects, and in particular an imbalance between extraembryonic and embryonic tissue development.

scholarly journals Multiscale analysis of single and double maternal-zygotic Myh9 and Myh10 mutants during mouse preimplantation development

2020 ◽  
Author(s):  
Markus Frederik Schliffka ◽  
Anna-Francesca Tortorelli ◽  
Özge Özgüç ◽  
Ludmilla de Plater ◽  
Oliver Polzer ◽  
...  
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Cell Number ◽  
Preimplantation Development ◽  
Mammalian Development ◽  
Mammalian Embryo ◽  
Fate Specification ◽  
Heavy Chains ◽  
A Cell ◽  
The Impact

AbstractDuring the first days of mammalian development, the embryo forms the blastocyst, the structure responsible for implanting the mammalian embryo. Consisting of an epithelium enveloping the pluripotent inner cell mass and a fluid-filled lumen, the blastocyst results from a series of cleavages divisions, morphogenetic movements and lineage specification. Recent studies identified the essential role of actomyosin contractility in driving the morphogenesis, fate specification and cytokinesis leading to the formation of the blastocyst. However, the preimplantation development of contractility mutants has not been characterized. Here, we generated single and double maternal-zygotic mutants of non-muscle myosin-II heavy chains (NMHC) to characterize them using multiscale imaging. We find that Myh9 (NMHC II-A) is the major NMHC during preimplantation development as its maternal-zygotic loss causes failed cytokinesis, increased duration of the cell cycle, weaker embryo compaction and reduced differentiation, whereas Myh10 (NMHC II-B) maternal-zygotic loss is much less severe. Double maternal-zygotic mutants for Myh9 and Myh10 show a much stronger phenotype, failing most attempts of cytokinesis. We find that morphogenesis and fate specification are affected but nevertheless carry on in a timely fashion, regardless of the impact of the mutations on cell number. Strikingly, even when all cell divisions fail, the resulting single-celled embryo can initiate trophectoderm differentiation and lumen formation by accumulating fluid in increasingly large vacuoles. Therefore, contractility mutants reveal that fluid accumulation is a cell-autonomous process and that the preimplantation program carries on independently of successful cell division.

scholarly journals The Ornithine Decarboxylase Gene Is Essential for Cell Survival during Early Murine Development

2001 ◽  
Vol 21 (19) ◽  
pp. 6549-6558 ◽  
Author(s):  
Hélène Pendeville ◽  
Nick Carpino ◽  
Jean-Christophe Marine ◽  
Yutaka Takahashi ◽  
Marc Muller ◽  
...  
Keyword(s):  
Cell Growth ◽  
Cell Survival ◽  
Ornithine Decarboxylase ◽  
Target Gene ◽  
Normal Development ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Blastocyst Stage ◽  
Biological Processes ◽  
Mammalian Development

ABSTRACT Overexpression and inhibitor studies have suggested that the c-Myc target gene for ornithine decarboxylase (ODC), the enzyme which converts ornithine to putrescine, plays an important role in diverse biological processes, including cell growth, differentiation, transformation, and apoptosis. To explore the physiological function of ODC in mammalian development, we generated mice harboring a disrupted ODC gene.ODC-heterozygous mice were viable, normal, and fertile. Although zygotic ODC is expressed throughout the embryo prior to implantation, loss of ODC did not block normal development to the blastocyst stage. Embryonic day E3.5 ODC-deficient embryos were capable of uterine implantation and induced maternal decidualization yet failed to develop substantially thereafter. Surprisingly, analysis of ODC-deficient blastocysts suggests that loss of ODC does not affect cell growth per se but rather is required for survival of the pluripotent cells of the inner cell mass. Therefore, ODC plays an essential role in murine development, and proper homeostasis of polyamine pools appears to be required for cell survival prior to gastrulation.

scholarly journals Multiscale analysis of single and double maternal-zygotic Myh9 and Myh10 mutants during mouse preimplantation development

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Markus Frederik Schliffka ◽  
Anna-Francesca Tortorelli ◽  
Özge Özgüç ◽  
Ludmilla de Plater ◽  
Oliver Polzer ◽  
...  
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Cell Number ◽  
Preimplantation Development ◽  
Mammalian Development ◽  
Mammalian Embryo ◽  
Fate Specification ◽  
Heavy Chains ◽  
A Cell ◽  
The Impact

During the first days of mammalian development, the embryo forms the blastocyst, the structure responsible for implanting the mammalian embryo. Consisting of an epithelium enveloping the pluripotent inner cell mass and a fluid-filled lumen, the blastocyst results from a series of cleavages divisions, morphogenetic movements and lineage specification. Recent studies identified the essential role of actomyosin contractility in driving the cytokinesis, morphogenesis and fate specification leading to the formation of the blastocyst. However, the preimplantation development of contractility mutants has not been characterized. Here, we generated single and double maternal-zygotic mutants of non-muscle myosin II heavy chains (NMHC) to characterize them with multiscale imaging. We find that Myh9 (NMHC II-A) is the major NMHC during preimplantation development as its maternal-zygotic loss causes failed cytokinesis, increased duration of the cell cycle, weaker embryo compaction and reduced differentiation, whereas Myh10 (NMHC II-B) maternal-zygotic loss is much less severe. Double maternal-zygotic mutants for Myh9 and Myh10 show a much stronger phenotype, failing most attempts of cytokinesis. We find that morphogenesis and fate specification are affected but nevertheless carry on in a timely fashion, regardless of the impact of the mutations on cell number. Strikingly, even when all cell divisions fail, the resulting single-celled embryo can initiate trophectoderm differentiation and lumen formation by accumulating fluid in increasingly large vacuoles. Therefore, contractility mutants reveal that fluid accumulation is a cell-autonomous process and that the preimplantation program carries on independently of successful cell division.

scholarly journals Aggregation recovers developmental plasticity in mouse polyploid embryos

2019 ◽  
Vol 31 (2) ◽  
pp. 404 ◽  
Author(s):  
Hiroyuki Imai ◽  
Wataru Fujii ◽  
Ken Takeshi Kusakabe ◽  
Yasuo Kiso ◽  
Kiyoshi Kano
Keyword(s):  
Mammalian Cells ◽  
Developmental Plasticity ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Embryonic Stem ◽  
Blastocyst Stage ◽  
Mammalian Development ◽  
Cellular Functions ◽  
Developmental Potential ◽  
Early Mammalian Development

Tetraploid embryos normally develop into blastocysts and embryonic stem cells can be established from tetraploid blastocysts in mice. Thus, polyploidisation does not seem to be so harmful during preimplantation development. However, the mechanisms by which early mammalian development accepts polyploidisation are poorly understood. In this study, we aimed to elucidate the effect of polyploidisation on early mammalian development and to further comprehend its tolerance using hyperpolyploid embryos produced by repetitive whole genome duplication. We successfully established several types of polyploid embryos (tetraploid, octaploid and hexadecaploid) and studied their developmental potential invitro. We demonstrated that all types of these polyploid embryos maintained the ability to develop to the blastocyst stage, which implies that mammalian cells might have basic cellular functions in implanted embryos, despite polyploidisation. However, the inner cell mass was absent in hexadecaploid blastocysts. To complement the total number of cells in blastocysts, a fused hexadecaploid embryo was produced by aggregating several hexadecaploid embryos. The results indicated that the fused hexadecaploid embryo finally recovered pluripotent cells in the blastocyst. Thus, our findings suggest that early mammalian embryos may have the tolerance and higher plasticity to adapt to hyperpolyploidisation for blastocyst formation, despite intense alteration of the genome volume.

scholarly journals Primitive endoderm differentiation: from specification to epithelium formation

2014 ◽  
Vol 369 (1657) ◽  
pp. 20130537 ◽  
Author(s):  
Stéphanie Hermitte ◽  
Claire Chazaud
Keyword(s):  
Molecular Mechanisms ◽  
Inner Cell Mass ◽  
Embryo Implantation ◽  
Cell Mass ◽  
Cell Lineage ◽  
Primitive Endoderm ◽  
Lineage Specification ◽  
Embryo Patterning ◽  
Cell Lineages ◽  
Endoderm Differentiation

In amniotes, primitive endoderm (PrE) plays important roles not only for nutrient support but also as an inductive tissue required for embryo patterning. PrE is an epithelial monolayer that is visible shortly before embryo implantation and is one of the first three cell lineages produced by the embryo. We review here the molecular mechanisms that have been uncovered during the past 10 years on PrE and epiblast cell lineage specification within the inner cell mass of the blastocyst and on their subsequent steps of differentiation.

221 HOXB9 IS DIFFERENTIALLY EXPRESSED IN THE TWO FIRST CELL LINES OF THE MAMMALIAN EMBRYO

2015 ◽  
Vol 27 (1) ◽  
pp. 200
Author(s):  
C. Sauvegarde ◽  
R. Rezsöhazy ◽  
I. Donnay
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Blastocyst Stage ◽  
Nuclear Staining ◽  
Mammalian Embryo ◽  
Mean Intensity ◽  
Whitney Test ◽  
Mann Whitney Test ◽  
The Mean

Hox proteins are transcription factors known to be essential for embryo patterning. The detection of some Hox transcripts in oocytes and early embryos suggests that they could play a role before gastrulation. We previously demonstrated Hoxb9 expression in oocytes and from the zygote to the blastocyst stage in the mouse and the bovine (Paul et al. 2011 Mol. Reprod. Dev. 78, 436). The protein is present at all stages and in all cells with a strong nuclear staining in both species. The objective of this study was to perform an in-depth study at the blastocyst stage to compare the level of the nuclear protein between the inner cell mass (ICM) and the trophectoderm (TE) from the early to the expanded blastocyst stage. In vitro produced bovine blastocysts were collected at Day 6, Day 7.5, and Day 8 post-insemination. Hoxb9 proteins were detected by whole-mount immunofluorescence. TE nuclei were strongly stained at all stages while from D6 but especially from D7.5, the level of HOXB9 seemed to decrease in ICM nuclei with an increasing heterogeneity of staining between ICM nuclei. A light and apparently stable staining was also observed in the cytoplasm. Confocal images were quantified (Nis-element 3.1, Nikon). For each cell of TE or ICM, the ratio between the mean intensity of the nucleus and the mean intensity of the corresponding total cytoplasm was calculated. Whatever the stages, TE ratios were significantly (Mann–Whitney test; P < 0.0001) higher than ICM ratios, suggesting that HOXB9 is present in higher amounts in TE than in ICM cells. This observation could be correlated with the reduced HOXB9 relative expression observed in blastocysts. Moreover, the proportion of blastocysts showing a reduction of HOXB9 staining in at least one nucleus significantly increased from Day 6 to Day 7.5 blastocysts and Day 8 blastocysts (from 26% to 74% or 85%, chi-squared test; P < 0.001). Mouse zygotes, collected from superovulated mice, were cultured in vitro and embryos were collected 72 h, 80 h, 92 h and 100 h post-hCG injection. A similar nuclear staining was observed in all cells until 80 h post-hCG injection, while heterogeneity of staining appeared in ICM cells 92 h post-hCG, but especially in 100 h post-hCG embryos. The quantitative study was performed only on this latest stage and confirmed the stronger staining in TE than in ICM nuclei (Mann–Whitney test; P < 0.0001) observed in the bovine. At this stage, 82% of blastocysts presented a reduced Hoxb9 staining in some or all ICM nuclei. In conclusion, Hoxb9 protein is detected in all blastocyst nuclei both in the mouse and in the bovine. However, the protein seems globally less abundant in the ICM than in the TE cells. Moreover, the percentage of bovine blastocysts showing a reduction in HOXB9 staining intensity in ICM nuclei increases with blastocyst expansion. These results suggest an involvement of Hoxb9 in cell lineage differentiation in mammals.C. S. holds a FRIA PhD grant from the FRS-FNRS (Belgium). This study is supported by the FRS-FNRS and by an Action de Recherche Concertée.

scholarly journals Loss of RBBP4 results in defective inner cell mass, severe apoptosis, hyperacetylated histones and preimplantation lethality in mice†

2020 ◽  
Vol 103 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Xiaosu Miao ◽  
Tieqi Sun ◽  
Holly Barletta ◽  
Jesse Mager ◽  
Wei Cui
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Cell Number ◽  
Blastocyst Stage ◽  
Lineage Specification ◽  
Mouse Embryo Development ◽  
Evolutionarily Conserved ◽  
Early Mouse

Abstract Retinoblastoma-binding protein 4 (RBBP4) (also known as chromatin-remodeling factor RBAP48) is an evolutionarily conserved protein that has been involved in various biological processes. Although a variety of functions have been attributed to RBBP4 in vitro, mammalian RBBP4 has not been studied in vivo. Here we report that RBBP4 is essential during early mouse embryo development. Although Rbbp4 mutant embryos exhibit normal morphology at E3.5 blastocyst stage, they cannot be recovered at E7.5 early post-gastrulation stage, suggesting an implantation failure. Outgrowth (OG) assays reveal that mutant blastocysts cannot hatch from the zona or can hatch but then arrest without further development. We find that while there is no change in proliferation or levels of reactive oxygen species, both apoptosis and histone acetylation are significantly increased in mutant blastocysts. Analysis of lineage specification reveals that while the trophoblast is properly specified, both epiblast and primitive endoderm lineages are compromised with severe reductions in cell number and/or specification. In summary, these findings demonstrate the essential role of RBBP4 during early mammalian embryogenesis.

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