title: Mouse blastomeres acquire ability to divide asymmetrically before compaction.
abstract: The mouse preimplantation embryo generates the precursors of trophectoderm (TE) and inner cell mass (ICM) during the 8- to 16-cell stage transition, when the apico-basal polarized blastomeres undergo divisions that give rise to cells with different fate. Asymmetric segregation of polar domain at 8-16 cell division generate two cell types, polar cells which adopt an outer position and develop in TE and apolar cells which are allocated to inner position as the precursors of ICM. It is still not know when the blastomeres of 8-cell stage start to be determined to undergo asymmetric division. Here, we analyze the frequency of symmetric and asymmetric divisions of blastomeres isolated from 8-cell stage embryo before and after compaction. Using p-Ezrin as the polarity marker we found that size of blastomeres in 2/16 pairs cannot be used as a criterion for distinguishing symmetric and asymmetric divisions. Our results showed that at early 8-cell stage, before any visible signs of cortical polarity, a subset of blastomeres had been already predestined to divide asymmetrically. We also showed that almost all of 8-cell stage blastomeres isolated from compacted embryo divide asymmetrically, whereas in intact embryos, the frequency of asymmetric divisions is significantly lower. Therefore we conclude that in intact embryo the frequency of symmetric and asymmetric division is regulated by cell-cell interactions.
authors.affiliation: Department of Embryology, Faculty of Biology, Institute of Zoology, University of Warsaw, Warsaw, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Humięcka
authors.affiliation: Department of Embryology, Faculty of Biology, Institute of Zoology, University of Warsaw, Warsaw, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Szpila
authors.affiliation: Department of Embryology, Faculty of Biology, Institute of Zoology, University of Warsaw, Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Kłoś
authors.affiliation: Department of Embryology, Faculty of Biology, Institute of Zoology, University of Warsaw, Warsaw, Poland.
authors.forename: Marek
authors.initials: M
authors.lastname: Maleszewski
authors.affiliation: Department of Embryology, Faculty of Biology, Institute of Zoology, University of Warsaw, Warsaw, Poland.
authors.forename: Katarzyna
authors.identifier: http://orcid.org/0000-0002-8805-725X
authors.initials: K
authors.lastname: Szczepańska
mesh_terms: D000818:Animals; D001755:Blastocyst; D001757:Blastomeres / Q000166:cytology* / Q000378:metabolism; D000071616:CDX2 Transcription Factor / Q000235:genetics / Q000378:metabolism; D002450:Cell Communication / Q000235:genetics / Q000502:physiology; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology* / Q000378:metabolism; D005260:Female; D051379:Mice; D000099149:Ezrin
chemical_list: D000071616:CDX2 Transcription Factor; D003598:Cytoskeletal Proteins; D000099149:Ezrin; C487514:Cdx2 protein, mouse