Question

In a Xenopus animal cap assay, Vegetal cells are placed next to cells from the top of the Animal pole. If we inject a VegT inhibitor into the Vegetal cells, what happens to the Animal cap cells? What happens to the Vegetal cells? Why?

Answer 1

The animal cap is a region of the Xenopus blastula and early gastrula stage embryo (6–12 h after fertilization). It is termed as “animal” because the upper, pigmented half of the egg and embryo is referred to as the animal hemisphere (as opposed to the lower, vegetal hemisphere). The animal hemisphere is so named both because it contributes most to the final body (the vegetal hemisphere being mostly for yolk storage) and because those cells that it is made of are the most motile, or animated, during development. The animal cap is a “cap” because it forms the roof of a large cavity—he blastocoel—throughout blastula and gastrula stages and it has the shape of a rather untidy skullcap.

Vegetal poles don’t differentitate but express genes that are specific to the endoderm. VegT is also localized predominantly but not entirely in the vegetal cells. VegT is a transcription factor, that induces animal cap cells to express both meso and endodermal markers. So if VegT inhibitor is injected into the vegetal cells, there will ablation of mainly endodermal markers and the animal cap cells are unable to produce the mesoderm and endoderm.As vegetal cells also express endoderm specific genes, VegT inbition also affects their endoderm forming capability.