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(Greek, blastos = sprout + cystos = cavity) or blastula, the term used to describe the hollow cellular mass that forms in early development. The blastocyst consists of cells forming an outer trophoblast layer, an inner cell mass and a fluid-filled cavity. The blastocyst inner cell mass is the source of true embryonic stem cells capable of forming all cell types within the embryo. In humans, this stage occurs in the first and second weeks after the zygote forms a solid cellular mass morula stage) and before implantation.
Some Recent Findings
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References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.
Tsukasa Takahashi, Kisaburo Hanazawa, Takashi Inoue, Kenya Sato, Ayako Sedohara, Junko Okahara, Hiroshi Suemizu, Chie Yagihashi, Masafumi Yamamoto, Tomoo Eto, Yusuke Konno, Hideyuki Okano, Makoto Suematsu, Erika Sasaki Birth of Healthy Offspring following ICSI in In Vitro-Matured Common Marmoset (Callithrix jacchus) Oocytes. PLoS ONE: 2014, 9(4);e95560 PMID:24751978 Md Saenz-de-Juano, F Marco-Jimenez, Mp Viudes-de-Castro, R Lavara, Js Vicente Direct Comparison of the Effects of Slow Freezing and Vitrification on Late Blastocyst Gene Expression, Development, Implantation and Offspring of Rabbit Morulae. Reprod. Domest. Anim.: 2014; PMID:24750498 Hiromasa Hara, Miho Tagiri, In-Sul Hwang, Masato Takahashi, Masumi Hirabayashi, Shinichi Hochi Adverse Effect of Cake Collapse on the Functional Integrity of Freeze-Dried Bull Spermatozoa. Cryobiology: 2014; PMID:24747720 Melanie L Sutton-McDowall, Robert Yelland, Keith L Macmillan, Rebecca L Robker, Jeremy G Thompson A study relating the composition of follicular fluid and blood plasma from individual Holstein dairy cows to the in vitro developmental competence of pooled abattoir-derived oocytes. Theriogenology: 2014; PMID:24746097 Benjamin L Kidder Derivation and manipulation of trophoblast stem cells from mouse blastocysts. Methods Mol. Biol.: 2014, 1150();201-12 PMID:24744000
Human Blastocyst Formation
|Blastocyst hatching from zona pellucida (mouse)||Blastocyst hatching from zona pellucida (human)|
Model Human Blastocyst Development
The following figure is from a recent study using video and genetic analysis of in vitro human development during week 1 following fertilization.
- EGA - embryonic genome activation
- ESSP - embryonic stage–specific pattern, four unique embryonic stage–specific patterns (1-4)
- Links: Figure with legend
Mouse Blastocyst Gene Expression
General gene expression patterns are indicated from genomic profiling.
- red - loss of maternal mRNAs
- green - activation of embryonic genome (EGA)
- purple - maternal gene activation (MGA)
- orange - continuous expression
Inner Cell Mass
This outer layer of cells is also called the "embryoblast", a cluster of cells located and attached on one wall of the outer trophoblast layer.
This outer layer of cells is also called the "trophectoderm" (TE) epithelium. A key function is for the transport of sodium (Na+) and chloride (Cl-) ions through this layer into the blastocoel.
Differentiation of this layer has been shown to be regulated by the transcription factors Tead4 and then Caudal-related homeobox 2 (Cdx2).
- trophectoderm transports of Na+ and Cl- ions through this layer into the blastocoel
- generates an osmotic gradient driving fluid across this epithelium
- distinct apical and basolateral membrane domains specific for transport
- facilitates transepithelial Na+ and fluid transport for blastocoel formation
- transport is driven by Na, K-adenosine triphosphatase (ATPase) in basolateral membranes of the trophectoderm 
At the blastocyst stage, mammalian development metabolism switches on anaerobic glycolysis metabolism to satisfy metabolic demands of growing blastocyst and formation of the blastocoel. This is thought to be driven by the integral membrane protein family of facilitative glucose transporters (GLUT or SLC2A).
- aerobic - oxidation of lactate and pyruvate via the citric acid cycle (Krebs cycle) and oxidative phosphorylation
- glycolysis- converts glucose into pyruvate
- GLUT - GLUcose Transporter (divided into 3 classes I-III)
- SLC2 - Solute Carrier Family 2
Glucose Transporter Expression
- GLUT1 - from zygote to blastocyst. (all mammalian tissues, basal glucose uptake)
- GLUT2 and GLUT3 - from late eight cell stage to blastocyst. (GLUT2, liver and pancreatic beta cells; GLUT3, all mammalian tissues, basal glucose uptake)
- GLUT4 - not expressed. (muscle and adipose tissue)
- GLUT8 - up-regulated at blastocyst stage. (central nervous system and heart)
- (Data mainly from mouse development, adult tissue expression shown in brackets)
A mouse study, has shown GLUT8 is up-regulated following insulin stimulation, though a more recent GLUT8 knockout mouse shows normal early embryonic development in the absence of this transporter.
Blastula Cell Communication
Two types of cell junctions have been identified located at different regions in the developing blastocyst.
| Tight junctions
Located close to outer surface create a seal, isolates interior of embryo from external medium.
| Gap junctions
Allow electrically coupling of the cells of epithelium surrounding the fluid-filled cavity.
Blastocyst Hatching - zona pellucida lost, ZP has sperm entry site, and entire ZP broken down by uterine secretions and possibly blastula secretions.
Uterine Glands - secretions required for blastocyst motility and nutrition
|At about day 5 the human blastocyst "hatches" out of the protective zona pellucida. This hatching allows increased growth, access to uterine nutrient secretions and blastocyst adhesion to the uterine lining. Associated with this hatching process are a series of physical contractions.
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Human blastocyst contractions (day 5-6)
- TEA DNA- binding domain, these factors bind to the consensus TEA/ATTS cognate binding site
- TEF-3 - renamed Tead1 and Tead4
- Tead3 - is expressed in the placental syncytiotrophoblasts
- E-cadherin - Calcium ion-dependent cell adhesion molecule, a cell membrane adhesive protein required for morula compaction
- epithin - A type II transmembrane serine protease, identified in mouse for compaction of the morula during preimplantation embryonic development. Expressed from 8-cell stage at blastomere contacts and co-localises in the morula with E-cadherin. PMID: 15848395
- Na, K-adenosine triphosphatase - A sodium potassium pump that generates an osmotic gradient for fluid flow into the blastocoel
- Zonula occludens-1 - (ZO-1) Tight junction protein involved in morula to blastocyst transformation in the mouse PMID: 18423437
Blastocyst in Other Species
Early mouse development model
- Links: Mouse Development
- Links: Bovine Development
- ↑ 1.0 1.1 Pu Zhang, Marco Zucchelli, Sara Bruce, Fredwell Hambiliki, Anneli Stavreus-Evers, Lev Levkov, Heli Skottman, Erja Kerkelä, Juha Kere, Outi Hovatta Transcriptome profiling of human pre-implantation development. PLoS ONE: 2009, 4(11);e7844 PMID:19924284 | PMC2773928 | PLoS One
- ↑ 2.0 2.1 2.2 Connie C Wong, Kevin E Loewke, Nancy L Bossert, Barry Behr, Christopher J De Jonge, Thomas M Baer, Renee A Reijo Pera Non-invasive imaging of human embryos before embryonic genome activation predicts development to the blastocyst stage. Nat. Biotechnol.: 2010, 28(10);1115-21 PMID:20890283 | Nat Biotechnol.
- ↑ Jason C Parks, Blair R McCallie, Ann M Janesch, William B Schoolcraft, Mandy G Katz-Jaffe Blastocyst gene expression correlates with implantation potential. Fertil. Steril.: 2011, 95(4);1367-72 PMID:20864103
- ↑ Yojiro Yamanaka, Fredrik Lanner, Janet Rossant FGF signal-dependent segregation of primitive endoderm and epiblast in the mouse blastocyst. Development: 2010, 137(5);715-24 PMID:20147376
- ↑ C Y Fong, A Bongso Comparison of human blastulation rates and total cell number in sequential culture media with and without co-culture. Hum. Reprod.: 1999, 14(3);774-81 PMID:10221713
- ↑ Noriko Tanaka, Takumi Takeuchi, Queenie V Neri, Eric Scott Sills, Gianpiero D Palermo Laser-assisted blastocyst dissection and subsequent cultivation of embryonic stem cells in a serum/cell free culture system: applications and preliminary results in a murine model. J Transl Med: 2006, 4();20 PMID:16681851 | PMC1479373 | J Transl Med.
- ↑ 7.0 7.1 Christine E Bell, Michele D Calder, Andrew J Watson Genomic RNA profiling and the programme controlling preimplantation mammalian development. Mol. Hum. Reprod.: 2008, 14(12);691-701 PMID:19043080 | Mol Hum Reprod.
- ↑ Noriyuki Nishioka, Shinji Yamamoto, Hiroshi Kiyonari, Hiroko Sato, Atsushi Sawada, Mitsunori Ota, Kazuki Nakao, Hiroshi Sasaki Tead4 is required for specification of trophectoderm in pre-implantation mouse embryos. Mech. Dev.: , 125(3-4);270-83 PMID:18083014
- ↑ Gerald M Kidder, Andrew J Watson Roles of Na,K-ATPase in early development and trophectoderm differentiation. Semin. Nephrol.: 2005, 25(5);352-5 PMID:16139691
- ↑ 10.0 10.1 M O Carayannopoulos, M M Chi, Y Cui, J M Pingsterhaus, R A McKnight, M Mueckler, S U Devaskar, K H Moley GLUT8 is a glucose transporter responsible for insulin-stimulated glucose uptake in the blastocyst. Proc. Natl. Acad. Sci. U.S.A.: 2000, 97(13);7313-8 PMID:10860996 | PMC16542 | Proc Natl Acad Sci U S A.
- ↑ Mathieu Membrez, Edith Hummler, Friedrich Beermann, Jacques-Antoine Haefliger, Rebecca Savioz, Thierry Pedrazzini, Bernard Thorens GLUT8 is dispensable for embryonic development but influences hippocampal neurogenesis and heart function. Mol. Cell. Biol.: 2006, 26(11);4268-76 PMID:16705176
- ↑ Sueo Niimura Time-lapse videomicrographic analyses of contractions in mouse blastocysts. J. Reprod. Dev.: 2003, 49(6);413-23 PMID:14967891
- ↑ K Yamazaki, Y Kato Sites of zona pellucida shedding by mouse embryo other than muran trophectoderm. J. Exp. Zool.: 1989, 249(3);347-9 PMID:2708952
- ↑ P Jacquemin, J J Hwang, J A Martial, P Dollé, I Davidson A novel family of developmentally regulated mammalian transcription factors containing the TEA/ATTS DNA binding domain. J. Biol. Chem.: 1996, 271(36);21775-85 PMID:8702974
- ↑ 15.0 15.1 15.2 15.3 15.4 Maria Keramari, Janet Razavi, Karen A Ingman, Christoph Patsch, Frank Edenhofer, Christopher M Ward, Susan J Kimber Sox2 is essential for formation of trophectoderm in the preimplantation embryo. PLoS ONE: 2010, 5(11);e13952 PMID:21103067 | PMC2980489 | PLoS One.
- ↑ Pawel Krupinski, Vijay Chickarmane, Carsten Peterson Simulating the mammalian blastocyst--molecular and mechanical interactions pattern the embryo. PLoS Comput. Biol.: 2011, 7(5);e1001128 PMID:21573197 | PMC3088645 | PLoS Comput Biol.
Theodore P Rasmussen, Gareth N Corry Epigenetic pre-patterning and dynamics during initial stages of mammalian preimplantation development. J. Cell. Physiol.: 2010, 225(2);333-6 PMID:20607796
Katie Cockburn, Janet Rossant Making the blastocyst: lessons from the mouse. J. Clin. Invest.: 2010, 120(4);995-1003 PMID:20364097
Janet Rossant Stem cells and lineage development in the mammalian blastocyst. Reprod. Fertil. Dev.: 2007, 19(1);111-8 PMID:17389140
Joana Santos, C Filipe Pereira, Aida Di-Gregorio, Thomas Spruce, Olivia Alder, Tristan Rodriguez, Véronique Azuara, Matthias Merkenschlager, Amanda G Fisher Differences in the epigenetic and reprogramming properties of pluripotent and extra-embryonic stem cells implicate chromatin remodelling as an important early event in the developing mouse embryo. Epigenetics Chromatin: 2010, 3();1 PMID:20157423
Bette J Dzamba, Karoly R Jakab, Mungo Marsden, Martin A Schwartz, Douglas W DeSimone Cadherin adhesion, tissue tension, and noncanonical Wnt signaling regulate fibronectin matrix organization. Dev. Cell: 2009, 16(3);421-32 PMID:19289087
Bhavwanti Sheth, Rachael L Nowak, Rebecca Anderson, Wing Yee Kwong, Thomas Papenbrock, Tom P Fleming Tight junction protein ZO-2 expression and relative function of ZO-1 and ZO-2 during mouse blastocyst formation. Exp. Cell Res.: 2008, 314(18);3356-68 PMID:18817772
Noriyuki Nishioka, Shinji Yamamoto, Hiroshi Kiyonari, Hiroko Sato, Atsushi Sawada, Mitsunori Ota, Kazuki Nakao, Hiroshi Sasaki Tead4 is required for specification of trophectoderm in pre-implantation mouse embryos. Mech. Dev.: , 125(3-4);270-83 PMID:18083014
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Cite this page: Hill, M.A. (2014) Embryology Blastocyst Development. Retrieved April 23, 2014, from http://embryology.med.unsw.edu.au/embryology/index.php?title=Blastocyst_Development
- Dr Mark Hill 2014, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G