Dev Growth Differ 2000 Dec 01;426:581-91. doi: 10.1046/j.1440-169x.2000.00539.x.

Localization and behavior of putative blastopore determinants in the uncleaved Xenopus egg.

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The present study examines putative blastopore determinants in uncleaved Xenopus eggs. Deletion of marginal and lower portions of Xenopus eggs when between 30 and 50% of the first cell cycle has been completed (0.3-0.5 normalized time (NT)) results in the complete absence of the blastopore, while deletion of the vegetal hemisphere during the same period leads to the formation of a smaller blastopore. Extrusion of only yolk and deep cytoplasm of the vegetal hemisphere during 0.3-0.5 NT does not affect the formation or size of the blastopore. Consistently, transplantation of cortical and subcortical cytoplasm from marginal, but not other, sites of eggs at 0.3-0.5 NT to an animal blastomere from 16-cell stage embryos induces an ectopic blastopore and bottle cell-like cells. This does not occur in the same transplantation from eggs at 0.2 NT. These results suggest that the blastopore determinants become localized to the marginal cortical and/or subcortical cytoplasm during 0.2-0.3 NT. Other results suggest the involvement of a hexyleneglycol-sensitive system in the process of localization of the blastopore determinants to the marginal region during 0.2-0.3 NT. The properties and behavior of the putative blastopore determinants are discussed in relation to those of VegT, which previously has been shown to induce ectopic blastopores.

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Species referenced: Xenopus laevis
Genes referenced: vegt