... synthesized in the Spemannorganizer, namely Follistatin, Chordin and Noggin[12]. These proteins are antagonists of BMP and othermembers of the TGF-b family, binding to and inhibit-ing these ... these signaling molecules from binding to theirreceptors in the extracellular space, thus inhibiting ven-tralizing activities. Of these proteins, Chordin has along-range effect. In Xenopus, ... may be vari-able depending on the situation of the cell or the tim-ing during embryogenesis.Nevertheless, the availability of mutant strains, gen-etic crosses, knockout and overexpression systemsmake...