Talk:Blastocyst Development

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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


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

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

Blastocyst Reviews

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."