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Cite this page: Hill, M.A. (2024, June 18) Embryology Morula. Retrieved from


Diversity of human and mouse homeobox gene expression in development and adult tissues

BMC Dev Biol. 2016 Nov 3;16(1):40.

Dunwell TL1, Holland PW2.

  • 20 human homeobox genes with widespread expression, primarily from the TALE, CERS and ZF classes.
  • Human - 8-cell and morula - 12 eutherian-specific homeobox genes not detectable outside of reproductive tissues or the embryo.
  • Mouse - four phases of homeobox gene expression - oocyte to zygote; 2-cell; 4-cell to blastocyst; early to mid post-implantation. The most dramatic shifts in homeobox gene expression are between 2-cell and 4-cell, and between blastocyst and post-implantation. Within this group there is a gradual shift in expression between e8.5 and e9.5 dominated by new expression of HOXL ANTP class genes.


BACKGROUND: Homeobox genes encode a diverse set of transcription factors implicated in a vast range of biological processes including, but not limited to, embryonic cell fate specification and patterning. Although numerous studies report expression of particular sets of homeobox genes, a systematic analysis of the tissue specificity of homeobox genes is lacking. RESULTS: Here we analyse publicly-available transcriptome data from human and mouse developmental stages, and adult human tissues, to identify groups of homeobox genes with similar expression patterns. We calculate expression profiles for 242 human and 278 mouse homeobox loci across a combination of 59 human and 12 mouse adult tissues, early and late developmental stages. This revealed 20 human homeobox genes with widespread expression, primarily from the TALE, CERS and ZF classes. Most homeobox genes, however, have greater tissue-specificity, allowing us to compile homeobox gene expression lists for neural tissues, immune tissues, reproductive and developmental samples, and for numerous organ systems. In mouse development, we propose four distinct phases of homeobox gene expression: oocyte to zygote; 2-cell; 4-cell to blastocyst; early to mid post-implantation. The final phase change is marked by expression of ANTP class genes. We also use these data to compare expression specificity between evolutionarily-based gene classes, revealing that ANTP, PRD, LIM and POU homeobox gene classes have highest tissue specificity while HNF, TALE, CUT and CERS are most widely expressed. CONCLUSIONS: The homeobox genes comprise a large superclass and their expression patterns are correspondingly diverse, although in a broad sense related to an evolutionarily-based classification. The ubiquitous expression of some genes suggests roles in general cellular processes; in contrast, most human homeobox genes have greater tissue specificity and we compile useful homeobox datasets for particular tissues, organs and developmental stages. The identification of a set of eutherian-specific homeobox genes peaking from human 8-cell to morula stages suggests co-option of new genes to new developmental roles in evolution. KEYWORDS: Embryo; Homeodomain; Organs; Transcription factor PMID: 27809766 PMCID: PMC5094009 DOI: 10.1186/s12861-016-0140-y


PC7 and the related proteases Furin and Pace4 regulate E-cadherin function during blastocyst formation

J Cell Biol. 2015 Sep 28;210(7):1185-97. doi: 10.1083/jcb.201503042.

Bessonnard S1, Mesnard D2, Constam DB1.


The first cell differentiation in mammalian embryos segregates polarized trophectoderm cells from an apolar inner cell mass (ICM). This lineage decision is specified in compacted morulae by cell polarization and adhesion acting on the Yes-associated protein in the Hippo signaling pathway, but the regulatory mechanisms are unclear. We show that morula compaction and ICM formation depend on PC7 and the related proprotein convertases (PCs) Furin and Pace4 and that these proteases jointly regulate cell-cell adhesion mediated by E-cadherin processing. We also mapped the spatiotemporal activity profiles of these proteases by live imaging of a transgenic reporter substrate in wild-type and PC mutant embryos. Differential inhibition by a common inhibitor revealed that all three PCs are active in inner and outer cells, but in partially nonoverlapping compartments. E-cadherin processing by multiple PCs emerges as a novel mechanism to modulate cell-cell adhesion and fate allocation. © 2015 Bessonnard et al.

PMID 26416966


Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage

Nat Commun. 2012;3:1251. doi: 10.1038/ncomms2249.

Chavez SL1, Loewke KE, Han J, Moussavi F, Colls P, Munne S, Behr B, Reijo Pera RA.


Previous studies have demonstrated that aneuploidy in human embryos is surprisingly frequent with 50-80% of cleavage-stage human embryos carrying an abnormal chromosome number. Here we combine non-invasive time-lapse imaging with karyotypic reconstruction of all blastomeres in four-cell human embryos to address the hypothesis that blastomere behaviour may reflect ploidy during the first two cleavage divisions. We demonstrate that precise cell cycle parameter timing is observed in all euploid embryos to the four-cell stage, whereas only 30% of aneuploid embryos exhibit parameter values within normal timing windows. Further, we observe that the generation of human embryonic aneuploidy is complex with contribution from chromosome-containing fragments/micronuclei that frequently emerge and may persist or become reabsorbed during interphase. These findings suggest that cell cycle and fragmentation parameters of individual blastomeres are diagnostic of ploidy, amenable to automated tracking algorithms, and likely of clinical relevance in reducing transfer of embryos prone to miscarriage.

PMID 23212380


Genetic disruption of aurora B uncovers an essential role for aurora C during early mammalian development

Development. 2011 Jul;138(13):2661-72. Epub 2011 May 25.

Fernández-Miranda G, Trakala M, Martín J, Escobar B, González A, Ghyselinck NB, Ortega S, Cañamero M, Pérez de Castro I, Malumbres M. Source Cell Division and Cancer Group, Spanish National Cancer Research Center (CNIO), Madrid, Spain.


Mitosis is controlled by multiple kinases that drive cell cycle progression and prevent chromosome mis-segregation. Aurora kinase B interacts with survivin, borealin and incenp to form the chromosomal passenger complex (CPC), which is involved in the regulation of microtubule-kinetochore attachments and cytokinesis. Whereas genetic ablation of survivin, borealin or incenp results in early lethality at the morula stage, we show here that aurora B is dispensable for CPC function during early cell divisions and aurora B-null embryos are normally implanted. This is due to a crucial function of aurora C during these early embryonic cycles. Expression of aurora C decreases during late blastocyst stages resulting in post-implantation defects in aurora B-null embryos. These defects correlate with abundant prometaphase figures and apoptotic cell death of the aurora B-deficient inner cell mass. Conditional deletion of aurora B in somatic cells that do not express aurora C results in chromosomal misalignment and lack of chromosome segregation. Re-expression of wild-type, but not kinase-dead, aurora C rescues this defect, suggesting functional overlap between these two kinases. Finally, aurora B-null cells partially arrest in the presence of nocodazole, suggesting that this kinase is not essential for the spindle assembly checkpoint.

PMID 21613325


Functional genomics of 5- to 8-cell stage human embryos by blastomere single-cell cDNA analysis

PLoS One. 2010 Oct 26;5(10):e13615.

Galán A, Montaner D, Póo ME, Valbuena D, Ruiz V, Aguilar C, Dopazo J, Simón C.

Valencia Node of The National Stem Cell Bank, Centro de Investigación Príncipe Felipe (CIPF), Valencia, Spain. Abstract Blastomere fate and embryonic genome activation (EGA) during human embryonic development are unsolved areas of high scientific and clinical interest. 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. All the human blastomeres from the 5- to 8-cell stage embryo displayed a common gene expression pattern corresponding to ICM markers (e.g., DDX3, FOXD3, LEFTY1, MYC, NANOG, POU5F1), stemness (e.g., POU5F1, DNMT3B, GABRB3, SOX2, ZFP42, TERT), and TE markers (e.g., GATA6, EOMES, CDX2, LHCGR). The EGA profile was also investigated between the 5-6- and 8-cell stage embryos, and compared to the blastocyst stage. Known genes (n = 92) such as depleted maternal transcripts (e.g., CCNA1, CCNB1, DPPA2) and embryo-specific activation (e.g., POU5F1, CDH1, DPPA4), as well as novel genes, were confirmed. 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. Finally, new EGA features in human embryogenesis are presented.

PMID 21049019


Regulation of compaction initiation in mouse embryo

Yi Chuan. 2009 Dec;31(12):1177-84. (Article in Chinese)

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

Department of Histology and Embryology, Harbin Medical University, Harbin 150081, Chin. Abstract Developmental events in preimplantation mouse embryos include the first cleavage, the activation of the embryonic genome, the compaction of the blastomeres to form morula (MO), and the formation of the blastocyst (BL). Compaction, the first cell differentiation event in mammalian development, occurs at the late eight-cell stage in the mouse and may be described in terms of some types of morphological change, which involve reorganization within a cell and intercellular reorganization. Surface microvilli became restricted to a few basal sites and to an externally facing (apical) pole. Prior to compaction, the blastomeres are spherical and lack specialized intercellular junctions. During compaction, the cells were flattened against one another, thus maximizing intercellular contact and obscuring intercellular boundaries. It is believed that the events of compaction have an important influence on the processes involved in blastocyst formation, namely the initiation of inner cell mass and trophectoderm differentiation. The inner cell mass will form the future embryo proper, whereas the trophectoderm cells will form only extraembryonic tissues. Compaction is initiated by E-cadherin mediated cell adhesion, which is regulated post-translationally via protein kinase C. With E-cadherin knock-out, maternal E-cadherin is able to mediate the compaction process at the morula stage. Initial adhesion is mediated by homophilic interactions between E-cadherin extracellular domains.In this review, we attempted to describe this process in detail.

PMID 20042384

Orientation of mitotic spindles during the 8- to 16-cell stage transition in mouse embryos

PLoS One. 2009 Dec 4;4(12):e8171.

Dard N, Louvet-Vallée S, Maro B.

CNRS, UMR7622-Laboratoire de Biologie Cellulaire du Développement, Paris, France. Abstract BACKGROUND: Asymmetric cell divisions are involved in the divergence of the first two lineages of the pre-implantation mouse embryo. They first take place after cell polarization (during compaction) at the 8-cell stage. It is thought that, in contrast to many species, spindle orientation is random, although there is no direct evidence for this.

METHODOLOGY/PRINCIPAL FINDINGS: Tubulin-GFP and live imaging with a spinning disk confocal microscope were used to directly study spindle orientation in whole embryos undergoing the 8- to 16-cell stage transition. This approach allowed us to determine that there is no predetermined cleavage pattern in 8-cell compacted mouse embryos and that mitotic spindle orientation in live embryo is only modulated by the extent of cell rounding up during mitosis.

CONCLUSIONS: These results clearly demonstrate that spindle orientation is not controlled at the 8- to 16-cell transition, but influenced by cell bulging during mitosis, thus reinforcing the idea that pre-implantation development is highly regulative and not pre-patterned.

PMID 19997595

Identification of mouse 8-cell embryo stage-specific genes by Digital Differential Display

Exp Anim. 2009 Oct;58(5):547-56.

Wang N, Xue L, Yuan A, Xu D.

College of Veterinary Medicine, Hunan Agricultural University, Hunan Province, P.R. China. Abstract Preimplantation development is critical for successful implantation and pregnancy. In the mouse preimplantation embryo, the first event of morphological and cellular differentiation is established during polarization and compaction at the 8-cell stage. The considerable cell surface and cytoplasmic changes and formation of different populations of cells at the 8-cell stage are fundamentally important for the development of all organisms. To determine genes that are specifically expressed at this crucial stage of embryo development and also to shed light on the different mechanisms that could be of importance during embryo development, we investigated mouse 8-cell and 4-cell embryo stage-specific genes using Digital Differential Display (DDD). The 8-cell stage-specific genes were sorted according to their ontology data from the Database for Annotation, Visualization and Integrated Discovery (DAVID), which outlines possible roles for the genes expressed at the 8-cell stage. This study highlights how online tools can be used to identify genes involved in embryo development. Identification of the 8-cell embryo stage-specific genes would open new opportunities for understanding molecular networks during the mid-preimplantation gene activation. Using bioinformatic tools, such as Digital Differential Display and DAVID, it will be possible to identify genes expressed at the 8-cell stage that are likely to be involved in mammalian preimplantation embryo development. Our results may provide a new foundation for molecular control at the onset of embryonic development in mammals, and should be of interest to the scientific community.

PMID 19897940


The four blastomeres of a 4-cell stage human embryo are able to develop individually into blastocysts with inner cell mass and trophectoderm

Hum Reprod. 2008 Aug;23(8):1742-7. Epub 2008 May 24.

Van de Velde H, Cauffman G, Tournaye H, Devroey P, Liebaers I.

Research Centre Reproduction and Genetics, Universitair Ziekenhuis Brussel (UZ Brussel), Laarbeeklaan 101, 1090 Brussels, Belgium. Abstract BACKGROUND: Early mammalian blastomeres are thought to be flexible and totipotent allowing the embryo to overcome perturbations in its organization during preimplantation development. In the past, experiments using single blastomeres from 2-, 4- and 8-cell stage mammalian embryos have provided evidence that at least some of the isolated cells can develop into healthy fertile animals and therefore are totipotent. We investigated whether isolated blastomeres of human 4-cell stage embryos could develop in vitro into blastocysts with trophectoderm (TE) and inner cell mass (ICM).

METHODS: Six 4-cell stage human embryos were split and the four blastomeres were cultured individually. The expression of NANOG, a marker for ICM cells, was analysed by immunocytochemistry.

RESULTS: The majority of the blastomere-derived embryos followed the normal pattern of development with compaction on Day 4 and cavitation on Day 5 and developed into small blastocysts with TE and ICM on Day 6 (n = 12). The four cells of one embryo were individually capable of developing into blastocysts with TE and ICM, and NANOG was expressed in the ICM.

CONCLUSIONS: Although based on a small number of embryos, we conclude that the blastomeres of a 4-cell stage human embryo are flexible and able to develop into blastocysts with ICM and TE.

PMID 18503052

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.

It is unknown whether or not tight junction formation plays any role in morula to blastocyst transformation that is associated with development of polarized trophoblast cells and fluid accumulation. Tight junctions are a hallmark of polarized epithelial cells and zonula occludens-1 (ZO-1) is a known key regulator of tight junction formation. Here we show that ZO-1 protein is first expressed during compaction of 8-cell embryos. This stage-specific appearance of ZO-1 suggests its participation in morula to blastocyst transition. Consistent with this idea, we demonstrate that ZO-1 siRNA delivery inside the blastomeres of zona-weakened embryos using electroporation not only knocks down ZO-1 gene and protein expressions, but also inhibits morula to blastocyst transformation in a concentration-dependent manner. In addition, ZO-1 inactivation reduced the expression of Cdx2 and Oct-4, but not ZO-2 and F-actin. These results provide the first evidence that ZO-1 is involved in blastocyst formation from the morula by regulating accumulation of fluid and differentiation of nonpolar blastomeres to polar trophoblast cells.

PMID 18423437

Ras-MAPK signaling promotes trophectoderm formation from embryonic stem cells and mouse embryos

Nat Genet. 2008 Jul;40(7):921-6. Epub 2008 Jun 8.

Lu CW, Yabuuchi A, Chen L, Viswanathan S, Kim K, Daley GQ.

Division of Pediatric Hematology and Oncology, Children's Hospital Boston and Dana Faber Cancer Institute, Boston, Massachusetts 02115, USA. Abstract In blastocyst chimeras, embryonic stem (ES) cells contribute to embryonic tissues but not extraembryonic trophectoderm. Conditional activation of HRas1(Q61L) in ES cells in vitro induces the trophectoderm marker Cdx2 and enables derivation of trophoblast stem (TS) cell lines that, when injected into blastocysts, chimerize placental tissues. Erk2, the downstream effector of Ras-mitogen-activated protein kinase (MAPK) signaling, is asymmetrically expressed in the apical membranes of the 8-cell-stage embryo just before morula compaction. Inhibition of MAPK signaling in cultured mouse embryos compromises Cdx2 expression, delays blastocyst development and reduces trophectoderm outgrowth from embryo explants. These data show that ectopic Ras activation can divert ES cells toward extraembryonic trophoblastic fates and implicate Ras-MAPK signaling in promoting trophectoderm formation from mouse embryos.

PMID 18536715

Tight junction protein ZO-2 expression and relative function of ZO-1 and ZO-2 during mouse blastocyst formation

Sheth B, Nowak RL, Anderson R, Kwong WY, Papenbrock T, Fleming TP.

School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO167PX, UK. Abstract Apicolateral tight junctions (TJs) between epithelial cells are multiprotein complexes regulating membrane polarity and paracellular transport and also contribute to signalling pathways affecting cell proliferation and gene expression. ZO-2 and other ZO family members form a sub-membranous scaffold for binding TJ constituents. We investigated ZO-2 contribution to TJ biogenesis and function during trophectoderm epithelium differentiation in mouse preimplantation embryos. Our data indicate that ZO-2 is expressed from maternal and embryonic genomes with maternal ZO-2 protein associated with nuclei in zygotes and particularly early cleavage stages. Embryonic ZO-2 assembled at outer blastomere apicolateral junctional sites from the late 16-cell stage. Junctional ZO-2 first co-localised with E-cadherin in a transient complex comprising adherens junction and TJ constituents before segregating to TJs after their separation from the blastocyst stage (32-cell onwards). ZO-2 siRNA microinjection into zygotes or 2-cell embryos resulted in specific knockdown of ZO-2 mRNA and protein within blastocysts. Embryos lacking ZO-2 protein at trophectoderm TJs exhibited delayed blastocoel cavity formation but underwent normal cell proliferation and outgrowth morphogenesis. Quantitative analysis of trophectoderm TJs in ZO-2-deficient embryos revealed increased assembly of ZO-1 but not occludin, indicating ZO protein redundancy as a compensatory mechanism contributing to the mild phenotype observed. In contrast, ZO-1 knockdown, or combined ZO-1 and ZO-2 knockdown, generated a more severe inhibition of blastocoel formation indicating distinct roles for ZO proteins in blastocyst morphogenesis.

PMID 18817772

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

Maternal beta-catenin and E-cadherin in mouse development

De Vries WN, Evsikov AV, Haac BE, Fancher KS, Holbrook AE, Kemler R, Solter D, Knowles BB.

Development. 2004 Sep;131(18):4435-45. Epub 2004 Aug 11.

PMID 15306566

Time from insemination to first cleavage predicts developmental competence of human preimplantation embryos in vitro

Hum Reprod. 2002 Feb;17(2):407-12.

Fenwick J, Platteau P, Murdoch AP, Herbert M. Source Reproductive Medicine, BioScience Centre, ICFL, Times Square, Newcastle upon Tyne NE1 4EP, UK.


BACKGROUND: The absence of reliable markers for the identification of viable embryos for transfer at the early cleavage stage is likely to contribute to the generally low implantation rates and high incidence of multiple gestation in IVF treatment. In this study, we investigate the relationship between timing of first cleavage and the incidence of blastocyst formation in vitro. METHODS: Couples (n = 70) with at least one embryo remaining after transfer were included in the analyses. All embryos (n = 579) were examined for early cleavage at 25 h after insemination. Following embryo transfer, the remaining embryos (n = 426) were cultured until day 7 of development, and assessed for blastocyst formation. RESULTS: Eighty-five embryos (14.7%) cleaved to the 2-cell stage within 25 h of insemination; 26 of these were selected for transfer on day 2. Of the 59 embryos remaining in culture, 19 (32.2%) developed to the blastocyst stage; this was a significantly higher number than was observed in embryos (61/367; 16.6%) that failed to cleave within 25 h of insemination (P < 0.01). Within these two groups of embryos the proportion of hatched blastocysts was 11/59 (18.6%) and 26/367 (7.1%) respectively (P < 0.005). CONCLUSIONS: These findings indicate that early cleavage is indicative of increased developmental potential in human embryos and may be useful as an additional criterion in the selection of embryos for transfer.

PMID 11821286