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#4-cell stage

2 public questions tagged with this topic.

Stem Cell -ll

The cells of the 4-cell stage mouse embryo are:

Mammalian embryo displays highly regulative development: early blastomeres retain remarkable flexibility and equipotency. Murine four-cell embryo blastomeres remain totipotent as demonstrated by ability of isolated single cell to contribute to both trophectoderm and inner cell mass compartments and to support full-term development when aggregated with carrier cells or transplanted into foster mothers. Single-nucleus RNA sequencing shows equal expression of Oct4 and Cdx2 potentiality. Potency restriction occurs at compaction and blastocyst stage when Cdx2 and Oct4 become mutually exclusive, separating trophoblast from pluripotent inner cell mass lineage irreversibly.

Ref: Tarkowski, Nature 1959; Tarkowski & Wroblewska 1967: Mouse 4-cell blastomeres totipotent contribution.

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C-Elegans Development-l

What happens if the P2 blastomere is removed at the 4-cell stage?

P2 blastomere provides inductive Wnt and Src signals to EMS at four-cell stage essential for endoderm. MOM-2 Wnt ligand from P2 activates MOM-5 Frizzled, WRM-1 beta-catenin asymmetry, LIT-1 Nemo kinase cascade in EMS, polarizing division into anterior MS and posterior E daughters. POP-1 TCF nuclear levels reduced posteriorly, permitting MED/END expression. If P2 is ablated surgically or genetically, extrinsic signal disappears, EMS defaults to MS-like fate, both daughters become muscle-pharynx precursors, endoderm marker ges-1 and elt-2 fail. Thus no intestine forms, demonstrating conditional specification.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 8: P2-EMS interaction - Wnt signaling induces endoderm in C. elegans.

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