Etude des embryons doubles mutants Nanog-/- ; Gata6-/- durant la spécification de la masse cellulaire interne. Mise en évidence d'une nouvelle hétérogénéité.

Abstract : During mouse blastocyst formation, the embryo consists of an outer epithelium, the trophectoderm (TE), and the inner cell mass (ICM). The epiblast (EPI) and the primitive endoderm (PrE) are specified within the MCI in a "salt and pepper" pattern characterized by the complementary expression of NANOG, marker of EPI and gata6, marker of PrE. Nanog is mandatory to acquire an EPI identity and Gata6 induces the PrE identity. FGF /MAPK pathway plays a critical role in the acquisition of a PrE identity and disruption of its activity directly impacts the PrE/Epi ratio within the ICM. I’m looking for factors that would be expressed heterogeneously before the specification of internal cells and might tilt the balance towards one fate or the other. For this, I dissected the evolution of ICM cells within Nanog-/- ; Gata6-/- embryos. These embryos form properly the TE and MCI that specifies neither EPI nor PrE. Indeed, the internal cells of Nanog-/- ; Gata6-/- embryos remain stuck around the stage of E3.25. Surprisingly, in the MCI cells, the transcription factor SOX2 is present and this, heterogeneously. Moreover, using inhibitors treatments of the FGF/MAPK pathway, I show that this pathway is not responsible for the heterogeneity of expression of SOX2. Thus, the heterogeneous expression of SOX2 in the inner cells of the embryos is therefore independent of Nanog, Gata6 and the FGF/MAPK pathway.
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Sabine Chauveau. Etude des embryons doubles mutants Nanog-/- ; Gata6-/- durant la spécification de la masse cellulaire interne. Mise en évidence d'une nouvelle hétérogénéité.. Médecine humaine et pathologie. Université d'Auvergne - Clermont-Ferrand I, 2016. Français. ⟨NNT : 2016CLF1MM29⟩. ⟨tel-02415208⟩

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