(Latin, morula = mulberry) An early stage in post-fertilization development when cells have rapidly mitotically divided to produce a solid mass of cells (12-15 cells) with a "mulberry" appearance. This stage is followed by formation of a cavity in this cellular mass blastocyst stage.
A key event prior to morula formation is "compaction", where the 8 cell embryo undergoes changes in cell morphology and cell-cell adhesion that initiates the formation of this solid ball of cells.
In humans, morula stage of development occurs during the first days of the first week following fertilization. This developmental stage is followed by formation of a cavity, the blastocoel, which defines formation of the blastocyst.
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.
Bas Brinkhof, Helena Ta van Tol, Marian Ja Groot Koerkamp, Frank M Riemers, Sascha G IJzer, Kaveh Mashayekhi, Henk P Haagsman, Bernard Aj Roelen A mRNA landscape of bovine embryos after standard and MAPK-inhibited culture conditions: a comparative analysis. BMC Genomics: 2015, 16(1);277 PMID: 25888366 Zubing Cao, Timothy S Carey, Avishek Ganguly, Catherine A Wilson, Soumen Paul, Jason G Knott Transcription factor AP-2γ induces early Cdx2 expression and represses HIPPO signaling to specify the trophectoderm lineage. Development: 2015; PMID: 25858457 Hidehiko Ogawa, Hiroyuki Watanabe, Atsushi Fukuda, Tomohiro Kono Deficiency of Genomic Reprogramming in Trophoblast Stem Cells Following Nuclear Transfer. Cell Reprogram: 2015, 17(2);115-123 PMID: 25826724 F Faustino, L C Makino, E Neumann, L S O Nakaghi Morphological and morphometric aspects of early life stages of piabanha Brycon gouldingi (Characidae). J. Fish Biol.: 2015; PMID: 25809317 Abolfazl Shirazi, Mahbobeh Heidari, Naser Shams-Esfandabadi, Amir Momeni, Zahra Derafshian Overexpression of signal transducers and activators of transcription in embryos derived from vitrified oocytesnegatively affect E-cadherin expression and embryo development. Cryobiology: 2015; PMID: 25794598
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- E-cadherin mediated adhesion initiates at compaction at the 8-cell stage
- regulated post-translationally via protein kinase C and other signalling molecules
An in vitro study of human blastocyst development showed that those blastomeres that initially divide quickly are more likely to develop to blastocyst stage.
A recent study in mice showed that there was no specific orientation of the mitotic spindle during cell division in the 8 to 16 cell stage transition. This suggests no predetermined cleavage pattern (pre-patterned) at the 8 cell stage and only modulated by the extent of cell rounding up during mitosis. In other species, such as the worm C.elegans and ascidians, have specific patterns of spindle orientation from the zygote stage.
Model Human Morula 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
Morulas in Other Species
- Links: Mouse Development
Sea Urchin Morula
Sea Urchin early embryo cleavage pattern (SDB Gallery Images)
- Links: Sea Urchin Development
- Image shows DNA staining (white) and f-actin filaments (orange) at day 4. Scale bars represent 100 µm.
- Pale staining round nuclei are at interphase.
- Arrow shows single nucleus at prophase.
- A single nucleus is seen at metaphase.
- Condensed bright nuclei are apoptotic.
- 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
- Galán A, Montaner D, Póo ME, Valbuena D, Ruiz V, Aguilar C, Dopazo J, Simón C. Functional genomics of 5- to 8-cell stage human embryos by blastomere single-cell cDNA analysis. PLoS One. 2010 Oct 26;5(10):e13615. PMID21049019 | PLoS One.
- 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.
- Nicolas Dard, Sophie Louvet-Vallée, Bernard Maro Orientation of mitotic spindles during the 8- to 16-cell stage transition in mouse embryos. PLoS ONE: 2009, 4(12);e8171 PMID: 19997595 | PLoS One.
- J Fenwick, P Platteau, A P Murdoch, M Herbert Time from insemination to first cleavage predicts developmental competence of human preimplantation embryos in vitro. Hum. Reprod.: 2002, 17(2);407-12 PMID: 11821286
- Sandra Leidenfrost, Marc Boelhauve, Myriam Reichenbach, Tuna Güngör, Horst-Dieter Reichenbach, Fred Sinowatz, Eckhard Wolf, Felix A Habermann Cell arrest and cell death in mammalian preimplantation development: lessons from the bovine model. PLoS ONE: 2011, 6(7);e22121 PMID: 21811561 | PLoS One.
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
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
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Cite this page: Hill, M.A. (2015) Embryology Morula. Retrieved April 28, 2015, from https://embryology.med.unsw.edu.au/embryology/index.php/Morula
- © Dr Mark Hill 2015, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G