Talk:Blastocyst Development

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2010

Individual blastomeres of 16- and 32-cell mouse embryos are able to develop into foetuses and mice

Dev Biol. 2010 Oct 7.

Tarkowski AK, Suwińska A, Czołowska R, Ożdżeński W.

Abstract Cell and developmental studies have clarified how, by the time of implantation, the mouse embryo forms three primary cell lineages: epiblast (EPI), primitive endoderm (PE), and trophectoderm (TE). However, it still remains unknown when cells allocated to these three lineages become determined in their developmental fate. To address this question, we studied the developmental potential of single blastomeres derived from 16- and 32-cell stage embryos and supported by carrier, tetraploid blastomeres. We were able to generate singletons, identical twins, triplets, and quadruplets from individual inner and outer cells of 16-cell embryos and, sporadically, foetuses from single cells of 32-cell embryos. The use of embryos constitutively expressing GFP as the donors of single diploid blastomeres enabled us to identify their cell progeny in the constructed 2n↔4n blastocysts. We showed that the descendants of donor blastomeres were able to locate themselves in all three first cell lineages, i.e., epiblast, primitive endoderm, and trophectoderm. In addition, the application of Cdx2 and Gata4 markers for trophectoderm and primitive endoderm, respectively, showed that the expression of these two genes in the descendants of donor blastomeres was either down- or up-regulated, depending on the cell lineage they happened to occupy. Thus, our results demonstrate that up to the early blastocysts stage, the destiny of at least some blastomeres, although they have begun to express markers of different lineage, is still labile.

Copyright © 2010. Published by Elsevier Inc. PMID: 20932967


Brg1 is required for Cdx2-mediated repression of Oct4 expression in mouse blastocysts

PLoS One. 2010 May 12;5(5):e10622.

Wang K, Sengupta S, Magnani L, Wilson CA, Henry RW, Knott JG.

Developmental Epigenetics Laboratory, Department of Animal Science, Michigan State University, East Lansing, Michigan, United States of America. Abstract During blastocyst formation the segregation of the inner cell mass (ICM) and trophectoderm is governed by the mutually antagonistic effects of the transcription factors Oct4 and Cdx2. Evidence indicates that suppression of Oct4 expression in the trophectoderm is mediated by Cdx2. Nonetheless, the underlying epigenetic modifiers required for Cdx2-dependent repression of Oct4 are largely unknown. Here we show that the chromatin remodeling protein Brg1 is required for Cdx2-mediated repression of Oct4 expression in mouse blastocysts. By employing a combination of RNA interference (RNAi) and gene expression analysis we found that both Brg1 Knockdown (KD) and Cdx2 KD blastocysts exhibit widespread expression of Oct4 in the trophectoderm. Interestingly, in Brg1 KD blastocysts and Cdx2 KD blastocysts, the expression of Cdx2 and Brg1 is unchanged, respectively. To address whether Brg1 cooperates with Cdx2 to repress Oct4 transcription in the developing trophectoderm, we utilized preimplantation embryos, trophoblast stem (TS) cells and Cdx2-inducible embryonic stem (ES) cells as model systems. We found that: (1) combined knockdown (KD) of Brg1 and Cdx2 levels in blastocysts resulted in increased levels of Oct4 transcripts compared to KD of Brg1 or Cdx2 alone, (2) endogenous Brg1 co-immunoprecipitated with Cdx2 in TS cell extracts, (3) in blastocysts Brg1 and Cdx2 co-localize in trophectoderm nuclei and (4) in Cdx2-induced ES cells Brg1 and Cdx2 are recruited to the Oct4 promoter. Lastly, to determine how Brg1 may induce epigenetic silencing of the Oct4 gene, we evaluated CpG methylation at the Oct4 promoter in the trophectoderm of Brg1 KD blastocysts. This analysis revealed that Brg1-dependent repression of Oct4 expression is independent of DNA methylation at the blastocyst stage. In toto, these results demonstrate that Brg1 cooperates with Cdx2 to repress Oct4 expression in the developing trophectoderm to ensure normal development.

PMID: 20485553

Non-invasive imaging of human embryos before embryonic genome activation predicts development to the blastocyst stage

Nat Biotechnol. 2010 Oct 3. [Epub ahead of print]

Wong CC, Loewke KE, Bossert NL, Behr B, De Jonge CJ, Baer TM, Pera RA.

[1] Institute for Stem Cell Biology and Regenerative Medicine, School of Medicine, Stanford University, Stanford, California, USA. [2] Department of Obstetrics and Gynecology, School of Medicine, Stanford University, Stanford, California, USA. [3] These authors contributed equally to this work. Abstract We report studies of preimplantation human embryo development that correlate time-lapse image analysis and gene expression profiling. By examining a large set of zygotes from in vitro fertilization (IVF), we find that success in progression to the blastocyst stage can be predicted with >93% sensitivity and specificity by measuring three dynamic, noninvasive imaging parameters by day 2 after fertilization, before embryonic genome activation (EGA). These parameters can be reliably monitored by automated image analysis, confirming that successful development follows a set of carefully orchestrated and predictable events. Moreover, we show that imaging phenotypes reflect molecular programs of the embryo and of individual blastomeres. Single-cell gene expression analysis reveals that blastomeres develop cell autonomously, with some cells advancing to EGA and others arresting. These studies indicate that success and failure in human embryo development is largely determined before EGA. Our methods and algorithms may provide an approach for early diagnosis of embryo potential in assisted reproduction.

PMID: 20890283

(CCC permission for reuse 7oct2010)


Imaging proprotein convertase activities and their regulation in the implanting mouse blastocyst

Mesnard D, Constam DB. J Cell Biol. 2010 Oct 4;191(1):129-39. Epub 2010 Sep 27.

Axis formation and allocation of pluripotent progenitor cells to the germ layers are governed by the TGF-β-related Nodal precursor and its secreted proprotein convertases (PCs) Furin and Pace4. However, when and where Furin and Pace4 first become active have not been determined. To study the distribution of PCs, we developed a novel cell surface-targeted fluorescent biosensor (cell surface-linked indicator of proteolysis [CLIP]). Live imaging of CLIP in wild-type and Furin- and Pace4-deficient embryonic stem cells and embryos revealed that Furin and Pace4 are already active at the blastocyst stage in the inner cell mass and can cleave membrane-bound substrate both cell autonomously and nonautonomously. CLIP was also cleaved in the epiblast of implanted embryos, in part by a novel activity in the uterus that is independent of zygotic Furin and Pace4, suggesting a role for maternal PCs during embryonic development. The unprecedented sensitivity and spatial resolution of CLIP opens exciting new possibilities to elucidate PC functions in vivo.


PMID: 20876279

http://www.ncbi.nlm.nih.gov/pubmed/20876279


New technique to quantify the lipid composition of lipid droplets in porcine oocytes and pre-implantation embryos using Nile Red fluorescent probe

Theriogenology. 2010 Sep 10. [Epub ahead of print]

Romek M, Gajda B, Krzysztofowicz E, Kepczynski M, Smorag Z.

Department of Cytology and Histology, Institute of Zoology, Jagiellonian University, R. Ingardena 6, 30-060 Krakow, Poland. Abstract The principal objective of this study was to develop a novel method based on confocal microscopy and a solvatochromic fluorescent dye, Nile red (NR) to quantify the main types of lipids in a single mammalian oocyte and embryo. We hypothesize that NR staining followed by the decomposition of NR-spectra identifies and quantifies the triglycerides, phospholipids, and cholesterol in a single oocyte and embryo. We analyzed the lipid droplets in porcine oocytes and pre-implantation embryos up to the hatched blastocyst stage developed in vivo and in cultured blastocysts. The emission spectrum of NR-stained mixture of different lipid types is a convolution of several component spectra. The principal component analysis (PCA) and a multivariate curve resolution-alternating least squares method (MCR-ALS) allowed to decompose the emission spectrum and quantify the relative amount of each lipid type present in mixture. We reported here that the level of the triglycerides, phospholipids and cholesterol in lipid droplets significantly decreases by 17.7%, 26.4% and 23.9%, respectively, from immature to mature porcine oocytes. The content of triglycerides and phospholipids remains unchanged in droplets of embryos from the zygote up to the morula stage. Then the triglyceride level decreases in the blastocyst by 15.1% and in the hatched blastocyst by 37.3%, whereas the amount of phospholipids decreases by 10.5% and 12.5% at the blastocyst and hatched blastocyst stages, respectively. In contrast, the content of cholesterol in droplets does not change during embryo cleavage. The lipid droplets in the blastocyst produced in vivo contain lower amounts of triglycerides (by 26.1%), phospholipids (by 14.2%) and cholesterol (by 34.8%) than those in the blastocyst cultured in NCSU-23 medium. In conclusion, our new technique is suitable to quantify the content of triglycerides, phospholipids and cholesterol in individual mammalian oocytes and embryos. Our findings indicate an important role for lipids during porcine oocyte maturation and early embryonic development, and suggest an altered lipid metabolism in cultured embryos.

PMID: 20833424


Number of blastomeres and distribution of microvilli in cloned mouse embryos during compaction

Zygote. 2010 Aug 25:1-6.

Li CB, Wang ZD, Zheng Z, Hu LL, Zhong SQ, Lei L.

Department of Histology and Embryology, Harbin Medical University, Harbin, China. Abstract SummaryThe events resulting in compaction have an important influence on the processes related to blastocyst formation. To analyse the quality of the embryos obtained by somatic cell nuclear transfer (SCNT) in aspects different from previous studies, not only the number of blastomeres of cloned embryos during the initiation of compaction, but also the distribution of microvilli in cloned, normal, parthenogenetic, and tetraploid embryos before and after compaction was preliminarily investigated in mouse. Our results showed that during compaction the number of blastomeres in SCNT embryos was fewer than that in intracytoplasmic sperm injection (ICSI) embryos and, before compaction, there was a uniform distribution of microvilli over the blastomere surface, but microvilli became restricted to an apical region after compaction in the four types of embryos. We also reported here that the time course of compaction in SCNT embryos was about 3 h delayed compared with that in ICSI embryos, while there was no significant difference between SCNT and ICSI embryos when developed to the 4-cell stage. We concluded that: (i) the cleavage of blastomeres in cloned embryos was slow at least before compaction; (ii) the distribution of microvilli in cloned, normal, parthenogenetic, and tetraploid embryos was coherent before and after compaction; and (iii) the initiation of compaction in SCNT embryos was delayed compared with that of ICSI embryos.

PMID: 20735894 http://www.ncbi.nlm.nih.gov/pubmed/20735894

Hatching and distribution of actin filaments in mouse blastocysts whose activities of protein kinase A were suppressed by H-89

J Reprod Dev. 2010 Feb;56(1):103-9. Epub 2009 Nov 2.

Suzuki R, Niimura S.

Graduate School of Science and Technology, Niigata University, Japan. Abstract The role of actin filaments and contractions in hatching was determined in mouse blastocysts whose actin filament bundling abilities had been suppressed by H-89, an inhibitor of protein kinase A. The hatching rate of blastocysts developed from morulae in a medium containing H-89 at a concentration of 4.0 microM was 17.2%, which was significantly lower than the 76.7% of the control blastocysts developed from morulae in a medium without H-89. The rates of blastocysts starting hatching and forming a slit in the zona pellucida were significantly lower in H-89-treated blastocysts (84.4 and 21.9%) than in control blastocysts (100.0 and 90.6%). The lengths of time needed for slit formation in the zona pellucida and for completion of hatching were significantly longer in the H-89-treated blastocysts (27.4 and 43.3 h) than in the control blastocysts (6.5 and 18.8 h). Over the course of 32 h after blastocoel formation, the number of strong contractions was similar in the H-89-treated and control blastocysts, but the number of weak contractions was significantly fewer in the H-89-treated blastocysts (2.41 times) than in the control blastocysts (4.19 times). Although the distribution of actin filaments was similar in the H-89-treated and control blastocysts in the pre-hatching, hatching and post-hatching periods, the rate of H-89-treated blastocysts in which most trophectoderm cells possessed the fluorescence of actin filaments (12.7%) was significantly lower than the 95.0% of the control blastocysts in the pre-hatching period. These results suggest that actin filament-mediated movements of trophectoderm cells contribute to hatching by facilitating the protrusion of trophectoderm cells from a small hole in the zona pellucida and by enlarging the protrusion. We also suggest that the low hatching ability of the treated blastocysts is related to weak contractions with a low frequency and to strong contractions requiring a longer time for re-expansion.

PMID: 19881218 http://www.ncbi.nlm.nih.gov/pubmed/19881218

Compaction

http://www.ncbi.nlm.nih.gov/pubmed/20042384

2008

Tead4 is required for specification of trophectoderm in pre-implantation mouse embryos

Nishioka N, Yamamoto S, Kiyonari H, Sato H, Sawada A, Ota M, Nakao K, Sasaki H.

Mech Dev. 2008 Mar-Apr;125(3-4):270-83. Epub 2007 Nov 17.

Laboratory for Embryonic Induction, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo, Kobe, Hyogo 650-0047, Japan. Abstract During pre-implantation mouse development, embryos form blastocysts with establishment of the first two cell lineages: the trophectoderm (TE) which gives rise to the placenta, and the inner cell mass (ICM) which will form the embryo proper. Differentiation of TE is regulated by the transcription factor Caudal-related homeobox 2 (Cdx2), but the mechanisms which act upstream of Cdx2 expression remain unknown. Here we show that the TEA domain family transcription factor, Tead4, is required for TE development. Tead1, Tead2 and Tead4 were expressed in pre-implantation embryos, and at least Tead1 and Tead4 were expressed widely in both TE and ICM lineages. Tead4-/- embryos died at pre-implantation stages without forming the blastocoel. The mutant embryos continued cell proliferation, and adherens junction and cell polarity were not significantly affected. In Tead4-/- embryos, Cdx2 was weakly expressed at the morula stage but was not expressed in later stages. None of the TE specific genes, including Eomes and a Cdx2 independent gene, Fgfr2, was detected in Tead4-/- embryos. Instead, the ICM specific transcription factors, Oct3/4 and Nanog, were expressed in all the blastomeres. Tead4-/- embryos also failed to differentiate trophoblast giant cells when they were cultured in vitro. ES cells with normal in vitro differentiation abilities were established from Tead4-/- embryos. These results suggest that Tead4 has a distinct role from Tead1 and Tead2 in trophectoderm specification of pre-implantation embryos, and that Tead4 is an early transcription factor required for specification and development of the trophectoderm lineage, which includes expression of Cdx2.

PMID: 18083014

http://www.ncbi.nlm.nih.gov/pubmed/18083014

2007

Compaction is initiated by E-cadherin mediated cell adhesion, which is regulated post-translationally via protein kinase C

Gene replacement reveals a specific role for E-cadherin in the formation of a functional trophectoderm. Kan NG, Stemmler MP, Junghans D, Kanzler B, de Vries WN, Dominis M, Kemler R. Development. 2007 Jan;134(1):31-41. Epub 2006 Nov 30. PMID: 17138661

"During mammalian embryogenesis the trophectoderm represents the first epithelial structure formed. The cell adhesion molecule E-cadherin is ultimately necessary for the transition from compacted morula to the formation of the blastocyst to ensure correct establishment of adhesion junctions in the trophectoderm. Here, we analyzed to what extent E-cadherin confers unique adhesion and signaling properties in trophectoderm formation in vivo. Using a gene replacement approach, we introduced N-cadherin cDNA into the E-cadherin genomic locus. We show that the expression of N-cadherin driven from the E-cadherin locus reflects the expression pattern of endogenous E-cadherin. Heterozygous mice co-expressing E- and N-cadherin are vital and show normal embryonic development. Interestingly, N-cadherin homozygous mutant embryos phenocopy E-cadherin-null mutant embryos. Upon removal of the maternal E-cadherin, we demonstrate that N-cadherin is able to provide sufficient cellular adhesion to mediate morula compaction, but is insufficient for the subsequent formation of a fully polarized functional trophectoderm. When ES cells were isolated from N-cadherin homozygous mutant embryos and teratomas were produced, these ES cells differentiated into a large variety of tissue-like structures. Importantly, different epithelial-like structures expressing N-cadherin were formed, including respiratory epithelia, squamous epithelia with signs of keratinization and secretory epithelia with goblet cells. Thus, N-cadherin can maintain epithelia in differentiating ES cells, but not during the formation of the trophectoderm. Our results point to a specific and unique function for E-cadherin during mouse preimplantation development."

Phosphorylation of ezrin on threonine T567 plays a crucial role during compaction in the mouse early embryo. Dard N, Louvet-Vallée S, Santa-Maria A, Maro B. Dev Biol. 2004 Jul 1;271(1):87-97. PMID: 15196952

2006

Cell and molecular regulation of the mouse blastocyst

Dev Dyn. 2006 Sep;235(9):2301-14.

Yamanaka Y, Ralston A, Stephenson RO, Rossant J.

Program of Developmental Biology, Hospital for Sick Children, Toronto, Ontario, Canada. Abstract Animals use diverse strategies to specify tissue lineages during development. A common strategy is to partition maternally supplied and localized lineage determinants into progenitor cells. The mouse embryo appears to use a different, more regulative strategy to specify the first three lineages: the epiblast (EPI: future embryo), the trophectoderm (TE: future placenta), and the primitive endoderm (PE: future yolk sac). These lineages are specified during two successive differentiation steps leading to formation of the blastocyst. Here, we review classic and contemporary models of early lineage specification in the mouse, and describe recent efforts to understand the molecular regulation of these events. We describe evidence that trophectoderm differentiation bears resemblance to the process of epithelialization and describe the importance of apical/basal protein complexes in regulating this process. Next, we present a revised model of PE specification, and describe evidence that PE cells in the inner cell mass sort out to occupy their ultimate position on the surface of the EPI. Finally, we describe factors that reinforce these lineages and three distinct stem cell types that can be isolated from them. Together, these mechanisms guide the differentiation of the first lineages of the mouse and thereby set up tissues that will be important for the first steps of embryonic body patterning.

Copyright 2006 Wiley-Liss, Inc. PMID: 16773657

http://onlinelibrary.wiley.com/doi/10.1002/dvdy.20844/full

Earlier

Expression of epithin in mouse preimplantation development: its functional role in compaction

Khang I, Sonn S, Park JH, Rhee K, Park D, Kim K. Dev Biol. 2005 May 1;281(1):134-44. PMID: 15848395

=A targeted mutation in the mouse E-cadherin gene results in defective preimplantation development

Riethmacher D, Brinkmann V, Birchmeier C. Proc Natl Acad Sci U S A. 1995 Jan 31;92(3):855-9. PMID: 7846066


Zonula occludens-1 (ZO-1) is involved in morula to blastocyst transformation in the mouse. Wang H, Ding T, Brown N, Yamamoto Y, Prince LS, Reese J, Paria BC. Dev Biol. 2008 Jun 1;318(1):112-25. Epub 2008 Mar 20. PMID: 18423437


Time-lapse videomicrographic analyses of contractions in mouse blastocysts

J Reprod Dev. 2003 Dec;49(6):413-23.

Niimura S.

Faculty of Agriculture, Niigata University, Japan. niimura@agr.niigata-u.ac.jp Abstract Contraction has been observed in cultured blastocysts of many mammals, but little is known about the features of the contraction and its physiological role in blastocysts. The author analyzed contractions of a large number of cultured mouse blastocysts by time-lapse videomicrography. The results revealed that blastocysts repeated contractions of different degrees during the expanded stage from 10 h after blastocoel formation, and that the number of contractions was greater during the hatching period than in the periods pre- and post-hatching. The results also showed that the time needed for both contraction and re-expansion to the size before contraction tended to lengthen in blastocysts severely contracted. It was inferred that contractions of blastocysts occur physiologically in relation to myosin light chain kinase, but not due to an increase in permeability between trophectoderm cells in association with their division, or the influence of culture. Furthermore, it was inferred that re-expansion of contracted blastocysts occurs due to active transport and accumulation of Na(+) from the trophectoderm cells into blastocoelic fluid as a result of the action of Na(+)/K(+)-ATPase activated in the membrane of trophectoderm cells. Our results suggested that contractions are also present in blastocysts developed in vivo, and that weak contractions (less than 20% volume reduction) play an important role in hatching, whereas strong contractions (20% or more volume reduction) have the effect of inhibiting hatching. From our results on contractions of various blastocysts, it seems possible to evaluate the developmental ability of embryos, i.e. embryo quality, based on contractions of blastocysts.

PMID: 14967891 http://www.ncbi.nlm.nih.gov/pubmed/14967891


Advanced embryo development during extended in vitro culture: observations of formation and hatching patterns in non-transferred human blastocysts

Hum Fertil (Camb). 2002 Nov;5(4):215-20.

Porter RN, Tucker MJ, Graham J, Sills ES.

Division of Cell Sciences, University of Southampton, Southampton S016 7PX, UK. Abstract Human embryos not chosen for fresh transfer or cryopreservation were maintained in extended in vitro culture for up to 9 days after fertilization to observe blastocyst formation and hatching features. These non-transferred embryos were derived from 64 consecutive IVF cycles, and were not cryopreserved either because of compromised morphology or because the patients did not consent to cryopreservation for personal reasons. Embryos were cultured individually to monitor daily growth until developmental arrest, and differential blastocyst formation and hatching were analysed among groups of patients and embryos. In the population studied, hatching occurred most commonly on day 7 after fertilization (range 5-9 days). A total of 301 blastocysts was observed, of which 116 (38.5%) eventually hatched in vitro irrespective of day of formation. A trend towards earlier blastocyst formation and a greater likelihood of hatching was noted in this population. Both blastocyst formation and hatching appeared negatively correlated with increasing maternal age and higher basal serum FSH concentrations on day 3 of development, although these trends did not reach statistical significance. Comparison of intracytoplasmic sperm injection (ICSI) (n = 25) and conventional insemination (n = 39) cycles showed a similar rate of blastocyst formation in both groups (54 and 52%, respectively; P > 0.05), but hatching patterns varied significantly between these groups (4.1 versus 61.6%, respectively; P < 0.0001). The discovery of marked impairment of hatching among non-transferred ICSI embryos supports the case for reconsideration of the appropriateness of assisted blastocyst hatching in selected cases.

PMID: 12477966 http://www.ncbi.nlm.nih.gov/pubmed/12477966

Regulation of blastocyst formation

Watson AJ, Barcroft LC. Front Biosci. 2001 May 1;6:D708-30. Review. PMID: 11333210

"Preimplantation or pre-attachment development encompasses the "free"-living period of mammalian embryogenesis, which directs development of the zygote through to the blastocyst stage. Blastocyst formation is essential for implantation, establishment of pregnancy and is a principal determinant of embryo quality prior to embryo transfer. Cavitation (blastocyst formation) is driven by the expression of specific sets of gene products that direct the acquisition of cell polarity within the trophectoderm, which is both the first epithelium of development and the outer cell layer encircling the inner cell mass of the blastocyst. Critical gene families controlling these events include: the E-cadherin-catenin cell adhesion family, the tight junction gene family, the Na/K-ATPase gene family and perhaps the aquaporin gene family. This review will update the roles of each of these gene families in trophectoderm differentiation and blastocyst formation. The current principal hypothesis under investigation is that blastocyst formation is mediated by a trans-trophectoderm ion gradient(s) established, in part, by Na/K-ATPase, which drives the movement of water through aquaporins (AQPs) across the epithelium into the extracellular space of the blastocyst to form the fluid-filled blastocoel. The trophectoderm tight junctional permeability seal regulates the leakage of blastocoel fluid, and also assists in the maintenance of a polarized Na/K-ATPase distribution to the basolateral plasma membrane domain of the mural trophectoderm. The cell-to-cell adhesion provided by the E-cadherin-catenin gene families is required for the establishment of the tight junction seal and the maintenance of the polarized Na/K-ATPase distribution. Blastocyst formation is therefore directly linked with trophectoderm cell differentiation, which arises through fundamental cell biological processes that are associated with the establishment of cell polarity."


http://www.ncbi.nlm.nih.gov/pubmed/1335276