Head induction by simultaneous repression of Bmp and Wnt signalling in Xenopus.
The Spemann organizer of the amphibian embryo can be subdivided into two discrete activities, namely trunk organizer and head organizer. Several factors secreted from the organizer that are involved in trunk organization are thought to act by repressing Bmp signalling. With the exception of the secreted factor cerberus, little is known about head-organizer inducers. Here we show that co-expression of a dominant-negative Bmp receptor with inhibitors of the Wnt-signalling pathway in Xenopus leads to the induction of complete secondary axes, including a head. This induction does not require expression of the siamois marker of Nieuwkoop centre signalling, suggesting that cells are directly shifting to head-organizer fate. Furthermore, we find that cerberus is a potent inhibitor of Wnt signalling. Our results indicate that head-organizer activity results from the simultaneous repression of Bmp and Wnt signalling and they suggest a mechanism for region-specific induction by the organizer.
Glinka
A
A
Division of Molecular Embryology, Deutches Krebsforschungszentrum, Heidelberg, Germany.
Wu
W
W
Onichtchouk
D
D
Blumenstock
C
C
Niehrs
C
C
D000818:Animals; D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D052004:Bone Morphogenetic Protein Receptors; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D046508:Culture Techniques; D004627:Embryonic Induction; D006257:Head / Q000196:embryology; D036341:Intercellular Signaling Peptides and Proteins; D011506:Proteins / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000378:metabolism; D017978:Receptors, Growth Factor; D015398:Signal Transduction; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D014981:Xenopus; D029867:Xenopus Proteins; D029961:Zebrafish Proteins
D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D036341:Intercellular Signaling Peptides and Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D017978:Receptors, Growth Factor; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; C525812:bmp4 protein, Xenopus; C525813:bmp4 protein, zebrafish; C100866:cer1 protein, Xenopus; D052004:Bone Morphogenetic Protein Receptors