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#early embryo

2 public questions tagged with this topic.

Fertilization in mammals-iv

Zygote asymmetry involves:

Early zygote asymmetry in plants, exemplified by Arabidopsis, involves polar distribution and differential gene expression establishing apical-basal axis before first division. WOX2 and WOX8 are WUSCHEL-related homeobox transcription factors marking apical and basal cell identities respectively after zygotic division. WOX2 promotes shoot lineage in apical daughter, WOX8 drives basal lineage leading to suspensor and root. Their asymmetric expression reflects pre-existing polarity in zygote and auxin transport. Oct4-Eomes-Nanog are mammalian pluripotency regulators not applicable to plant zygote; WOX network provides analogous molecular polarity mechanism instructing differential fate from single fertilized cell in embryogenesis.

Ref: Breuninger et al., Nature Genetics 2008: WOX2 and WOX8 regulating apical-basal polarity in Arabidopsis zygote asymmetry.

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Fertilization in mammals-iv

Essential ions for compaction:

Compaction transforms loosely adherent eight-cell mammalian morula into tightly apposed epithelium-like structure, prerequisite for blastocyst formation. Process depends critically on extracellular calcium enabling homophilic interaction of E-cadherin (uvomorulin) between blastomeres. Calcium stabilizes cadherin extracellular domains, allowing adherens junction formation and recruitment of catenins and actin cytoskeleton. This strengthens intercellular adhesion, induces cell polarization, peripheral microvilli loss and basolateral sealing. Chelation of calcium with EGTA reverses compaction, demonstrating calcium-cadherin-catenin axis indispensability for morula polarization and subsequent lineage specification via Hippo pathway.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 9: Morula compaction - E-cadherin, calcium dependence and Hippo signaling polarization.

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