Question

Explain the following observation in detail. What is happens at every stage? Why does this happen?

In the axolotl white mutant, NCCs fail to leave the neural tube. When wild-type neural crests are transplanted into mutant embryos, the crest cells are unable to migrate. However, when crests from mutant embryos are transplanted into wild-type embryos, their cells migrate normally

Answer 1

The dorsal region of neural tube produces BMPs which activate Wnt genes. When somites cease making Noggin, the neural tube BMPs are activate the migration of NCCs from neural tube. The Wnt and BMP signals together stimulate the cells destined to be neural crest to express Snail and Rho family proteins. When the Snail2 or Rho protein is inactivated or inhibited in NCCs, they fail to migrate from the neural tube.

Thus the neural crest in the mutant type is normal but the NCCs fail to migrate due to inactivation or inhibition of Snail2 or Rho protein. Due to this the transplantation of wild type neural crests into mutant embryos has no effect.

Since the neural crests of mutant type are normal and the neural crest of wild type embryos is normal, the transplantation of mutant neural crests into wild type resutls in migration of NCCs.