Abstract:Animals use diverse strategies to specify tissue lineages during development. A common strategy is to partition maternally supplied and localized lineage determinants into progenitor cells. The mouse embryo appears to use a different, more regulative strategy to specify the first three lineages: the epiblast (EPI: future embryo), the trophectoderm (TE: future placenta), and the primitive endoderm (PE: future yolk sac). These lineages are specified during two successive differentiation steps leading to formatio… Show more
“…Mammalian morula is transformed to the blastocyst through delamination. In mammalian embryogenesis, cell fate is specified at the 8-cell stage by the establishment of cell polarity (Yamanaka et al 2006;Johnson 2009) along the radius of early morula. Subsequent cell divisions lead to symmetric or asymmetric distribution of polarity information, based on the angle of cell division.…”
A topological inevitability of early developmental events through the use of classical topological concepts is discussed. Topological dynamics of forms and maps in embryo development are presented. Forms of a developing organism such as cell sets and closed surfaces are topological objects. Maps (or mathematical functions) are additional topological constructions in these objects and include polarization, singularities and curvature. Topological visualization allows us to analyze relationships that link local morphogenetic processes and integral developmental structures and also to find stable spatio-temporal topological characteristics that are invariant for a taxonomic group. The application of topological principles reveals a topological imperative: certain topological rules define and direct embryogenesis. A topological stability of embryonic morphogenesis is proposed and a topological scenario of developmental and evolutionary transformations is presented.
“…Mammalian morula is transformed to the blastocyst through delamination. In mammalian embryogenesis, cell fate is specified at the 8-cell stage by the establishment of cell polarity (Yamanaka et al 2006;Johnson 2009) along the radius of early morula. Subsequent cell divisions lead to symmetric or asymmetric distribution of polarity information, based on the angle of cell division.…”
A topological inevitability of early developmental events through the use of classical topological concepts is discussed. Topological dynamics of forms and maps in embryo development are presented. Forms of a developing organism such as cell sets and closed surfaces are topological objects. Maps (or mathematical functions) are additional topological constructions in these objects and include polarization, singularities and curvature. Topological visualization allows us to analyze relationships that link local morphogenetic processes and integral developmental structures and also to find stable spatio-temporal topological characteristics that are invariant for a taxonomic group. The application of topological principles reveals a topological imperative: certain topological rules define and direct embryogenesis. A topological stability of embryonic morphogenesis is proposed and a topological scenario of developmental and evolutionary transformations is presented.
“…Aux trois lignages cellulaires présents à l'implantation, l'Epi, le Tr et l'EPr, correspondent trois modèles in vitro de cellules souches [3]. Les trois types de cellules souches sont isolés à partir de blastocystes (E3,5).…”
Section: Cellules Souches Issues Du Blastocysteunclassified
“…ces molécules au cours des divisions symétriques et asymétriques ainsi que leur localisation baso-laté-rale ou apicale maintiennent la polarité des cellules externes [2,3]. Par exemple, lorsque l'aPKC ou ParD3, exprimées au pôle apical des cellules polarisées, sont inactivées dans certaines cellules, ces cellules ont tendance à se localiser à l'intérieur de l'embryon [12].…”
Section: Revuesunclassified
“…Les cellules pré-Epi et pré-EPr sont mélangées en « poivre et sel » dans la MCI à E3,5 [3,40]. Un jour plus tard, ces types cellulaires forment deux tissus bien séparés, l'épithélium de l'EPr recouvrant la masse de cellules épiblastiques.…”
Section: Formation De L'épithélium De L'eprunclassified
“…Le la masse cellulaire interne (MCI) qui sera à l'origine du futur embryon, le trophectoderme, futur placenta, et l'endoderme primitif qui constituera avec le mésoderme extraembryonnaire le futur sac vitellin. L'établissement de ces lignages est finement régulé et plusieurs mécanismes expliquant l'apparition et le maintien des premières différenciations cellulaires ont été proposés [1]. Chez les métazoaires, la voie de signalisation Notch est un mode fondamental de communication entre cellules voisines [2,3].…”
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