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Spemann organizer

Friday 28 May 2004

In 1924, Spemann and Mangold demonstrated the induction of Siamese twins in transplantation experiments with salamander eggs.

Spemann and Mangold discovered the extraordinary inductive potency of the dorsal blastopore lip in amphibian embryos.

Recent work in amphibian embryos has followed their lead and uncovered that cells in signalling centres that are located at the dorsal and ventral poles of the gastrula embryo communicate with each other through a network of secreted growth-factor antagonists, a protease that degrades them, a protease inhibitor and bone-morphogenic-protein (BMPs) signals.

Many inducers released by this organizer have now been identified and they typically encode antagonists of bone morphogenetic proteins (BMPs), Nodal growth factors or Wnt growth factors.

The different expression domains of these growth factors and their antagonists create signalling gradients, which pattern the early embryo in a combinatorial fashion and explain the regional specificities of head, trunk and tail organizers.

References

- De Robertis EM. Spemann’s organizer and self-regulation in amphibian embryos. Nat Rev Mol Cell Biol. 2006 Apr;7(4):296-302. PMID: 16482093

- Niehrs C. Regionally specific induction by the Spemann-Mangold organizer. Nat Rev Genet. 2004 Jun;5(6):425-34. PMID: 15153995