Morula

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Introduction

Human morula (day 2)[1]

(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.


Links: Fertilization | Week 1 | Morula | Blastocyst

Some Recent Findings

Human morula (day 3)[1]
  • Functional genomics of 5- to 8-cell stage human embryos by blastomere single-cell cDNA analysis[2] "Forty-nine blastomeres from 5- to 8-cell human embryos have been investigated following an efficient single-cell cDNA amplification protocol to provide a template for high-density microarray analysis. The previously described markers, characteristic of Inner Cell Mass (ICM) (n = 120), stemness (n = 190) and Trophectoderm (TE) (n = 45), were analyzed, and a housekeeping pattern of 46 genes was established. ...In summary, the global single-cell cDNA amplification microarray analysis of the 5- to 8-cell stage human embryos reveals that blastomere fate is not committed to ICM or TE.
  • Non-invasive imaging of human embryos before embryonic genome activation predicts development to the blastocyst stage[3] "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)."

Movies

Model embryo to 32 cell stage icon.jpg
 ‎‎Morula Model
Page | Play

Movies

Compaction

  • E-cadherin mediated adhesion initiates at compaction at the 8-cell stage
  • regulated post-translationally via protein kinase C and other signalling molecules

Blastomere Division

Spindle orientation calculation.[4]

An in vitro study of human blastocyst development[5] 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.[4] 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[3] using video and genetic analysis of in vitro human development during week 1 following fertilization.

Model human blastocyst development.jpg

  • 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

Mouse Morula


Links: Mouse Development

Sea Urchin Morula

Sea Urchin- early embryo cleavage pattern.jpg

Sea Urchin early embryo cleavage pattern (SDB Gallery Images)


Links: Sea Urchin Development

Bovine Morula

Bovine morula 01.jpg

Bovine Morula[6]

  • 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.


Links: Bovine Development | Mitosis

References

  1. 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. 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.
  3. 3.0 3.1 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.
  4. 4.0 4.1 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.
  5. 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
  6. 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.


Articles

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. (2014) Embryology Morula. Retrieved August 22, 2014, from https://php.med.unsw.edu.au/embryology/index.php?title=Morula

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© Dr Mark Hill 2014, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G