Henson s node

In chick embryos, although the BMP inhibitors noggin and chordin are expressed in the organizer (Henson s node), they fail to induce neural cell differentiation (Streit et al., 1998). In addition, the temporal expression of BMP inhibitors in chick embryos does not coincide with the induction of neural cells, suggesting that the roles of BMPs and their inhibitors in chick neurulation are not as clear-cut as that found in Xenopus (Streit and Stern, 1999). Furthermore gene-targeting experiments in mice have shown that normal neural differentiation occurs in the absence of BMP inhibitors (Matzuk et al., 1995 McMahon et al., 1998 Bachiller et al., 2000). 

Fig. 12.3. Stages in the development of the chick embryo, (a) Blastoderm before invagination of the mesoderm, (b) Blastoderm after the formation of the primitive streak and Henson s node, mesoderm cells forming from the epiblast. (c) Neural fold stage, (d) Differentiation of the somites into sderoderm, myotome and dermatome.

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