Sunday, February 10, 2019
Formation of the Trophectoderm Lineage Essay -- Anatomy, Cell Division
Formation of the trophectoderm declension. The root kiosk fate finality in mammalian development.The essential outcome of the early mammalian development is the attachment of the fertilized egg to the uterine lining. The cell population that leave alone support this attachment, the trophectoderm (TE), is distinguished from the inner cell mass (ICM) at the blastocyst stage and this separation represents the earliest lineage restriction. Up to the 8-cell stage, the embryo is characterized by a loose structure, unless thus compaction follows, a phenomenon mediated by increase cell-cell adhesion (tight junctions, increased E-cadherin expression). Acquisition of a microvillus apical membrane domain, polarization of the cytoplasm and shakeup of cytoskeleton elements establish apicobasal polarity while blastomeres become flattened. (Gilbert, Fleming et al., 2001). Still at this stage, whole cells prevail communication with their environment, but after sequential divisions they eith er issuing an inner or outer position in the late morula. By 32-cell stage, the blastocoel cavity is formed surrounded by the TE that will give rise to extraembryonic tissues (extraembryonic ectoderm and the trophoblast). Attached to one side of the TE epithelium, the ICM will form the embryo proper and nontrophoblast extraembryonic tissues. The molecular mechanisms behind this low gear differentiation event remain elusive. Clarification of these mechanisms will contribute to our intellect of early mammalian development and will support the field of block cell biology and induced pluripotency.Conservative versus differantiative cell divisions.After the compacted morula, the embryo undergoes two rounds of cleavage, during which the two cell populations become gr... ...(Cdx2, Eomes, Fgfr2) were re-expressed after the introduction of exogenic Sox2. Therefore, Sox2 was suggested as an early player in the introduction of the TE lineage, but interactions with the other transcription al regulators as well as actual contribution or not of maternal Sox2 mRNA still essential to be illuminated.From each the above, it is understood that the transcriptional network regulating the first cell fate decision is complicated and yet not clearly defined. Recent evidence supports a dual role of Klf5 in lineage specification (Fig 4). Upregulation of Klf5 is critical for TE development (upstream of Cdx2 and in parallel to Fgf signal), whereas low levels of Klf5 are needed to maintain the expression of Oct4 and Nanog in the ICM. Still, the exact mechanism and the interactions with other members of the network need to be examined (Lin., et al., 2010).
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