13 research outputs found
Cellular and molecular mechanisms of primitive streak morphogenesis and nascent mesoderm migration during mouse embryonic development
No full textLa gastrulation est un évènement complexe qui nécessite, en plus de la spécification et la différentiation des tissus embryonnaires, des mouvements cellulaire coordonnés et des réarrangements tissulaires. Nous avons utilisé la gastrulation chez l’embryon de souris comme modèle pour investiguer les mécanismes cellulaires et moléculaires de la transition épithélio- mésenchymateurse (EMT), suivi par la migration cellulaire. En utilisant des lignées génétiquement modifiées (expression transgénique de marqueurs fluorescents), de la culture ex vivo d’embryons in toto, et de l’imagerie confocale et à feuille de lumière en temps réel, nous avons étudié la formation de la ligne primitive (LP, le site où se passe la gastrulation) et la formation de nouvelles cellules de mésoderme, et également participé à la compréhension du rôle des Rho GTPases, régulateurs du cytosquelette cellulaire. Nous avons observé la formation de « rosettes » (un arrangement cellulaire formé par au moins 5 cellules) dans l’épiblaste postérieur à une fréquence supérieure comparée aux faces latérales et antérieure lors de l’initiation de la LP. Une partie des rosettes évoluent en «marguerites» durant l’ingression de cellules, probablement du à une division mitotique. Le marquage du Phospho-Histone H3 a mis en évidence des noyaux mitotiques sur le côté basal seulement dans l’épiblaste postérieur, et cela durant tout la fenêtre de formation de la LP. Ces divisions non-apicales résultent dans la formation d’une ou deux nouvelles cellules de mésoderme, suggérant un nouveau rôle de la mitose dans le cadre de la gastrulation chez les mammifères.Le marquage mosaïque de cellules de mésoderme a permis de suivre le comportement des cellules quittant la LP. Nos données montrent que le mode de migration, la signature transcriptionnelle et le cytosquelette de ces cellules diffèrent dans la région embryonnaire par rapport à la région extra- embryonnaire.Nous avons disséqué le rôle des GTPases dans le processus de gastrulation en analysant des mutants conditionnels spécifiques de l’épiblaste pour RhoA et le GEF (Guanine Exchange Factor) Ect2, un activateur de Rho et Rac, dont l’homologue chez la mouche est nécessaire pour la gastrulation. Le mutant spécifique de l'épiblaste de RhoA présente une accumulation de cellules dans la région embryonnaire postérieure, tandis que le mutant Ect2 présente un territoire embryonnaire considérablement réduit. En utilisant la même approche, le mutant spécifique de l'épiblaste de Cdk1 a également montré une diminution drastique de l’épiblaste embryonnaire et une mort cellulaire massive, indiquant un rôle crucial pour ces gènes dans la gastrulation et la morphogenèse précoce de la souris.Globalement, nos données permettent de mieux comprendre les processus cellulaires et moléculaires intervenant au cours de la gastrulation de l'embryon de souris.Doctorat en Sciences biomédicales et pharmaceutiques (Médecine)info:eu-repo/semantics/nonPublishe
Visualizing Mouse Embryo Gastrulation Epithelial-Mesenchymal Transition Through Single Cell Labeling Followed by Ex Vivo Whole Embryo Live Imaging.
No full textEpithelial-mesenchymal transition (EMT) is often studied in pathological contexts, such as cancer or fibrosis. This chapter focuses on physiological EMT that allows the separation of germ layers during mouse embryo gastrulation. In order to record individual cells behavior with high spatial and temporal resolution live imaging as they undergo EMT, it is very helpful to label the cells of interest in a mosaic fashion so as to facilitate cell segmentation and quantitative image analysis. This protocol describes the isolation, culture, and live imaging of E6.5-E7.5 mouse embryos mosaically labeled in the epiblast, the epithelium from which mesoderm and endoderm layers arise through EMT at gastrulation.info:eu-repo/semantics/publishe
Mechanisms of primitive streak morphogenesis and nascent mesoderm ingression during mouse embryo gastrulation
No full textImaging nascent mesoderm migration in mouse embryo highlights cell-environment interdependence
No full textUncovering the Number and Clonal Dynamics of Mesp1 Progenitors during Heart Morphogenesis.
No full textThe heart arises from distinct sources of cardiac progenitors that independently express Mesp1 during gastrulation. The precise number of Mesp1 progenitors that are specified during the early stage of gastrulation, and their clonal behavior during heart morphogenesis, is currently unknown. Here, we used clonal and mosaic tracing of Mesp1-expressing cells combined with quantitative biophysical analysis of the clonal data to define the number of cardiac progenitors and their mode of growth during heart development. Our data indicate that the myocardial layer of the heart derive from ∼250 Mesp1-expressing cardiac progenitors born during gastrulation. Despite arising at different time points and contributing to different heart regions, the temporally distinct cardiac progenitors present very similar clonal dynamics. These results provide insights into the number of cardiac progenitors and their mode of growth and open up avenues to decipher the clonal dynamics of progenitors in other organs and tissues
Distinct mesoderm migration phenotypes in extra-embryonic and embryonic regions of the early mouse embryo
No full textIn mouse embryo gastrulation, epiblast cells delaminate at the primitive streak to form mesoderm and definitive endoderm, through an epithelial-mesenchymal transition. Mosaic expression of a membrane reporter in nascent mesoderm enabled recording cell shape and trajectory through live imaging. Upon leaving the streak, cells changed shape and extended protrusions of distinct size and abundance depending on the neighboring germ layer, as well as the region of the embryo. Embryonic trajectories were meandrous but directional, while extra-embryonic mesoderm cells showed little net displacement. Embryonic and extra-embryonic mesoderm transcriptomes highlighted distinct guidance, cytoskeleton, adhesion, and extracellular matrix signatures. Specifically, intermediate filaments were highly expressed in extra-embryonic mesoderm, while live imaging for F-actin showed abundance of actin filaments in embryonic mesoderm only. Accordingly, Rhoa or Rac1 conditional deletion in mesoderm inhibited embryonic, but not extra-embryonic mesoderm migration. Overall, this indicates separate cytoskeleton regulation coordinating the morphology and migration of mesoderm subpopulations.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
RNASeq_mouse embryo mesoderm
No full textThis file contains the following excel files: Sample list, Expression levels, Ranked list of differential expressio
Asymmetry in the frequency and position of mitosis in the mouse embryo epiblast at gastrulation.
No full textAt gastrulation, a subpopulation of epiblast cells constitutes a transient posteriorly located structure called the primitive streak, where cells that undergo epithelial-mesenchymal transition make up the mesoderm and endoderm lineages. Mouse embryo epiblast cells were labelled ubiquitously or in a mosaic fashion. Cell shape, packing, organization and division were recorded through live imaging during primitive streak formation. Posterior epiblast displays a higher frequency of rosettes, some of which associate with a central cell undergoing mitosis. Cells at the primitive streak, in particular delaminating cells, undergo mitosis more frequently than other epiblast cells. In pseudostratified epithelia, mitosis takes place at the apical side of the epithelium. However, mitosis is not restricted to the apical side of the epiblast, particularly on its posterior side. Non-apical mitosis occurs specifically in the streak even when ectopically located. Posterior non-apical mitosis results in one or two daughter cells leaving the epiblast layer. Cell rearrangement associated with mitotic cell rounding in posterior epiblast, in particular when non-apical, might thus facilitate cell ingression and transition to a mesenchymal phenotype.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
An asymmetry in the frequency and position of mitosis in the epiblast precedes gastrulation and suggests a role for mitotic rounding in cell delamination during primitive streak epithelial-mesenchymal transition
No full textinfo:eu-repo/semantics/publishedin revision a EMBO Report
