Summary
A signalling region in the amphibian gastrula that induces a second body axis when transplanted.
In depth
Dorsal lip of the blastopore in amphibians. It secretes BMP antagonists, Wnt inhibitors and others to neuralise ectoderm and pattern mesoderm. Equivalents: Hensen's node in chick and node in mouse.
The organiser's activity depends on Wnt and Nodal. It secretes noggin, chordin and follistatin, which bind BMP. This 'default' model says ectoderm becomes neural without BMP.
Key idea: it is the signalling centre that organises the body axis.
In 1924 Hans Spemann and Hilde Mangold transplanted the dorsal lip of the blastopore from one newt gastrula to the ventral side of another. The graft induced a second neural plate and a nearly complete second body axis, giving a conjoined twin. The tissue was named the organiser.
Spemann won the 1935 Nobel Prize. The organiser secretes antagonists of BMP, Wnt and Nodal (noggin, chordin, Dkk) and later forms the notochord and head structures. Equivalents are the shield in zebrafish, Hensen's node in chick and the node in mice.
Example: graft experiments showed that host cells, not only graft cells, made the new axis.
Key idea: signals from a small region can pattern a whole embryo.
Frequently asked questions
What is Spemann Organiser?
A signalling region in the amphibian gastrula that induces a second body axis when transplanted.
Which area of biology covers Spemann Organiser, and how advanced is it?
Spemann Organiser is one of the 54 topics in Developmental Biology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Induction, BMP and TGF-Beta Signalling, Limb Development.
Can you give an example of Spemann Organiser?
Grafting a dorsal lip into the ventral side makes a conjoined twin tadpole.
What should I learn before Spemann Organiser?
Work through the Beginner topics in Developmental Biology first, such as Fertilisation, Zygote, Embryo, then return to Spemann Organiser. Advanced topics assume the Intermediate vocabulary.
What topics are related to Spemann Organiser?
The closest topics to Spemann Organiser are Induction, BMP and TGF-Beta Signalling, Limb Development, Body Axes Formation. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Spemann Organiser?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Spemann Organiser. To practise the whole of Developmental Biology, use the Developmental Biology quiz.
How is Spemann Organiser different from Induction?
Spemann Organiser: A signalling region in the amphibian gastrula that induces a second body axis when transplanted. Induction: One group of cells signals a neighbouring group to change its developmental path. Read both side by side and note what each one explains.
How should I study Spemann Organiser step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Induction and explain the difference aloud. Finally, take the Developmental Biology quiz and come back to this page for any question you miss.