title: The first two cell-fate decisions of preimplantation mouse embryo development are not functionally independent.
abstract: During mouse preimplantation embryo development, three distinct cell lineages are formed, represented by the differentiating trophectoderm (TE), primitive endoderm (PrE) and the pluripotent epiblast (EPI). Classically, lineage derivation has been presented as a two-step process whereby outer TE cells are first segregated from inner-cell mass (ICM), followed by ICM refinement into either the PrE or EPI. As ICM founders can be produced following the fourth or fifth cleavage divisions, their potential to equally contribute to EPI and PrE is contested. Thus, modelling the early sequestration of ICM founders from TE-differentiation after the fourth cleavage division, we examined ICM lineage contribution of varying sized cell clones unable to initiate TE-differentiation. Such TE-inhibited ICM cells do not equally contribute to EPI and PrE and are significantly biased to form EPI. This bias is not caused by enhanced expression of the EPI marker Nanog, nor correlated with reduced apical polarity but associated with reduced expression of PrE-related gene transcripts (Dab2 and Lrp2) and down-regulation of plasma membrane associated Fgfr2. Our results favour a unifying model were the three cell lineages are guided in an integrated, yet flexible, fate decision centred on relative exposure of founder cells to TE-differentiative cues.
authors.affiliation: Laboratory of Developmental Biology &Genetics (LDB&G), Department of Molecular Biology, Faculty of Science, University of South Bohemia, Branišovská 31, 37005 České Budějovice, CZECH REPUBLIC.
authors.forename: Aleksandar I
authors.initials: AI
authors.lastname: Mihajlović
authors.affiliation: Laboratory of Developmental Biology &Genetics (LDB&G), Department of Molecular Biology, Faculty of Science, University of South Bohemia, Branišovská 31, 37005 České Budějovice, CZECH REPUBLIC.
authors.forename: Vasanth
authors.initials: V
authors.lastname: Thamodaran
authors.affiliation: Laboratory of Developmental Biology &Genetics (LDB&G), Department of Molecular Biology, Faculty of Science, University of South Bohemia, Branišovská 31, 37005 České Budějovice, CZECH REPUBLIC.|Institute of Entomology Biology Centre of the Czech Academy of Sciences, Branišovská 31, 37005 České Budějovice, CZECH REPUBLIC.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Bruce
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology* / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000166:cytology* / Q000196:embryology; D047108:Embryonic Development / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout