title: Random Allocation of Blastomere Descendants to the Trophectoderm and ICM of the Bovine Blastocyst.
abstract: The first lineage specification during mammalian embryo development can be visually distinguished at the blastocyst stage. Two cell lineages are observed on the embryonic-abembryonic axis of the blastocyst: the inner cell mass and the trophectoderm. The timing and mechanisms driving this process are still not fully understood. In mouse embryos, cells seem prepatterned to become certain cell lineage because the first cleavage plane has been related with further embryonic-abembryonic axis at the blastocyst stage. Nevertheless, this possibility has been very debatable. Our objective was to determine whether this would be the case in another mammalian species, the bovine. To achieve this, cells of in vitro produced bovine embryos were traced from the 2-cell stage to the blastocyst stage. Blastocysts were then classified according to the allocation of the labeled cells in the embryonic and/or abembryonic part of the blastocyst. Surprisingly, we found that there is a significant percentage of the embryos (∼60%) with labeled and nonlabeled cells randomly distributed and intermingled. Using time-lapse microscopy, we have identified the emergence of this random pattern at the third to fourth cell cycle, when cells started to intermingle. Even though no differences were found on morphokinetics among different embryos, these random blastocysts and those with labeled cells separated by the embryonic-abembryonic axis (deviant pattern) are significantly bigger; moreover deviant embryos have a significantly higher number of cells. Interestingly, we observed that daughter cells allocation at the blastocyst stage is not affected by biopsies performed at an earlier stage.
authors.affiliation: Child Health, Obstetrics and Gynecology, School of Medicine, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Lessly P
authors.initials: LP
authors.lastname: Sepulveda-Rincon
authors.affiliation: UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy en Josas, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Dube
authors.affiliation: UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy en Josas, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Adenot
authors.affiliation: UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy en Josas, France.
authors.forename: Ludivine
authors.initials: L
authors.lastname: Laffont
authors.affiliation: UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy en Josas, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Ruffini
authors.affiliation: UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy en Josas, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Gall
authors.affiliation: Child Health, Obstetrics and Gynecology, School of Medicine, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Bruce K
authors.initials: BK
authors.lastname: Campbell
authors.affiliation: UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy en Josas, France.
authors.forename: Veronique
authors.initials: V
authors.lastname: Duranthon
authors.affiliation: UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy en Josas, France nathalie.beaujean@inserm.fr.|Univ Lyon, Université de Lyon 1, Inserm, Bron, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Beaujean
authors.affiliation: Child Health, Obstetrics and Gynecology, School of Medicine, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Walid E
authors.initials: WE
authors.lastname: Maalouf
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology* / Q000378:metabolism; D001757:Blastomeres / Q000166:cytology* / Q000378:metabolism; D002417:Cattle; D019070:Cell Lineage / Q000502:physiology*; D019175:DNA Methylation; D047108:Embryonic Development / Q000502:physiology*; D006657:Histones / Q000378:metabolism
chemical_list: D006657:Histones
keywords: H3 arginine methylation; blastocyst; embryo biopsy; patterning; preimplantation development; time-lapse microscopy