Frog axis cheat sheet

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Frog axis cheat sheet – Zoo 470 2013 – Page 2 (b) Vegetal cells signal to induce mesoderm: Dorsal vegetal cells are capable of inducing an axis and rescuing UV-treated embryos: (c) This leads to the “Nieuwkoop Center”, a region on the dorsal side that induces Organizer, whereas non-dorsal cells induce non-dorsal mesoderm: Note: Based on cell marking experiments, dorsal endoderm generates dorsal-type mesoderm in the experiment shown in (B), whereas non-dorsal types of endoderm induce non-dorsal types of mesoderm. Gilbert, 8e, Fig. 10.20 Gilbert, 8e, Fig. 10.21
Frog axis cheat sheet – Zoo 470 2013 – Page 3 Modern Experiments The challenge of modern developmental biology is to correlate classical experiments with molecular mechanisms. While much progress has been made in this area, there are still areas that are poorly understood. The establishment of the D-V axis involves several steps: Step 1: Fertilization induces cortical rotation. Cortical rotation is driven by microtubules, which in part are formed via nucleation from the sperm aster. The sperm enters 180° away from the future dorsal side of the embryo. In some species, this creates a lighter area on the surface known as the gray crescent. Step 2: Cortical rotation activates dorsal development, possibly through Dishevelled, GBP, and XWnt11. This leads to more β-catenin on the dorsal side of the zygote. Excess β-catenin introduced ventrally by overexpression can result in axis duplication (see figure below). Conversely, loss of βcatenin via morpholinos in dorsal vegetal cells leads to a ventralized embryo (not shown). Wolpert et al, 2e, Fig. 3.8 Gilbert, 9e, Fig. 7.1 Gilbert, 9e, Fig. 7.21
Page 1: Axis Specification: Amphibians Clas
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Frog axis cheat sheet

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