Signaling pathways and tissue interactions in neural plate border formation

Abstract

The neural crest is a transient cell population that gives rise to various cell types of multiple tissues and organs in the vertebrate embryo. Neural crest cells arise from the neural plate border, a region localized at the lateral borders of the prospective neural plate. Temporally and spatially coordinated interaction with the adjacent tissues, the non-neural ectoderm, the neural plate and the prospective dorsolateral mesoderm, is required for neural plate border specification. Signaling molecules, namely BMP, Wnt and FGF ligands and corresponding antagonists are derived from these tissues and interact to induce the expression of neural plate border specific genes. The present mini-review focuses on the current understanding of how the NPB territory is formed and accentuates the need for coordinated interaction of BMP and Wnt signaling pathways and precise tissue communication that are required for the definition of the prospective NC in the competent ectoderm.

Keywords: BMP; GDF6; Neural plate border; Recessive Robinow Syndrome; Ror2; Wnt; neural crest; neurocristophathies.

Figure 1.

Schematic and simplified illustration of BMP/Smad, Wnt/β-Catenin and β-Catenin independent Wnt pathways.

Figure 2.

Expression of diffusible growth factors and antagonists in blastula and early gastrula stage in Xenopus and chick embryos. In blastula stages, BMP ligands are expressed in the ectoderm and their expression is antagonized by secreted BMP antagonists. In Xenopus these are derived from the Blastula Chordin and Noggin Expressing center (BCNE⁹¹). In early gastrula stages, BMP ligands are expressed in the ectoderm and BMP antagonists are continuously expressed in the presumptive anterior neural plate ectoderm and in the dorsal marginal zone (DMZ). BMP4, GDF6, FGF and Wnt8 as well as BMP and Wnt antagonists are derived from the DLMZ. In chick blastulae, FGF is expressed in the entire epiblast, BMPs, Wnts only in the lateral epiblast and Chordin is expressed in a subset of pre-node epiblast cells and the multi-specific Wnt/BMP and Nodal antagonist Cerberus is secreted by the hypoblast (for review see ref.  and references therein). In gastrula stages, BMP4 is expressed in the entire NPB area, the anterior NPB additionally expresses the Wnt antagonists sFRP2 and Frzb1. Wnts and FGFs are expressed in the primitive streak and the node, the latter further expresses Chordin.