Talk:Morula

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. zl2007cb@yahoo.com.cn 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 http://www.ncbi.nlm.nih.gov/pubmed/20042384

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. hilde.vandevelde@uzbrussel.be 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.

http://www.ncbi.nlm.nih.gov/pubmed/18503052

http://humrep.oxfordjournals.org/content/23/8/1742.long

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