Figure 7Model of the Molecular Interaction of CV2, Chordin, Tsg, and BMP4 (A) Model of the regulation of D-V patterning by a network of extracellular proteins secreted by the dorsal and ventral centers of the Xenopus gastrula. Arrows in black indicate direct protein-protein interactions in the extracellular space, blue arrows transcriptional regulation by the BMP-responsive transcription factors Smad1/5/8, and the red arrow the hypothetical flux of Chordin/ADMP/BMP from the dorsal toward the ventral center of the embryo, where it would bind to CV2. This model of D-V patterning is self-regulating because at low BMP levels the transcription of the BMP-like molecule ADMP is activated, and at high BMP levels the BMP antagonist CV2 and the tolloid inhibitor Sizzled are upregulated (Reversade and De Robertis, 2005, Lee et al., 2006). The function of Tsg is to both increase BMP inhibition by CV2 and Chd and to promote BMP4 signaling in their absence. The tolloid protease Xlr cleaves Chordin/ADMP/BMP complexes, releasing active BMPs concentrated on the ventral side. (B) Model in which Chordin flow would help transport BMPs and Chordin from the dorsal to the ventral side of the Xenopus embryo. Three possible outcomes are indicated.
Image published in: Ambrosio AL et al. (2008)
Copyright © 2008. Image reproduced with permission of the Publisher, Elsevier B. V.
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