Question

20. Which of the following statements is FALSE regarding frog gastrulation

1. Migration of mesoderm cells require the fibronectin-integrin interaction

2. Mesoderm cells move into the blastocoel cavity by involution

3. Dorsal mesoderm cells undergo both involution and convergent extension

4. Convergent extension drives the elongation of dorsal mesoderm cells

5. Endoderm cells intercalate into the blastocoel cavity

Answer 1

The wrong answer is 3

because Frog (Xenopus), as well as other amphibian, gastrulation serves as an excellent example of the role of convergent extension in embryogenesis. During gastrulation in frogs, the driving force of convergent extension is the morphogenic activity of the presumptive dorsal mesodermal cells; this activity is driven by the mesenchymal cells that lie beneath the presumptive mesodermal and neural tissues.

During Xenopus gastrulation α5β1 integrin function is modulated in a temporally and spatially restricted manner, however, the regulatory mechanisms behind this regulation remain uncharacterized. Here we report that XGIPC/kermit2 binds to the cytoplasmic domain of the α5 subunit and regulates the activity of α5β1 integrin. The interaction of kermit2 with α5β1 is essential for fibronectin (FN) matrix assembly during the early stages of gastrulation.