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. Author manuscript; available in PMC: 2008 Apr 28.
Published in final edited form as: Int J Dev Biol. 2001;45(1):189–197.

Fig. 2. The organizer is a source of secreted antagonists that bind growth factors in the extracellular space.

Fig. 2

Three different types of extracellular modulators were been discovered in the organizer. All three have been shown to encode secreted inhibitors. Chordin, Noggin and Follistatin bind to BMPs and thereby inhibit them from activating their receptor. Frzb-1 and Dkk-1 antagonize Xwnt-8 in the extracellular space. Cerberus is a multivalent inhibitor of three different signals, BMPs, Xwnt-8 and the Xenopus Nodal-related mesoderm-inducing molecules (Xnr1, 2 and 4).