Our finding reveals a novel feedback loop mechanism based on the exchange of Fgf8 and Agr signaling between neural and non-neural compartments at the anterior margin of the neural plate and demonstrates a key role of Ras-dva1 in this mechanism.
These investigations demonstrate that hdMO1 embryos are deficient only in the very anterior margin of the neural plate and suggest a possible role for htt in the formation of this region.
Recently, we have shown that in the Xenopus laevis embryo, the small GTPase Ras-dva1, which is expressed near ANB, is necessary for the Fgf8-mediated expression of the telencephalic regulator FoxG1 (previously named BF1) in cells at the anterior margin of the neural plate (Tereshina et al., 2006).
During vertebrate embryonic development, chromatophores are one of a number of cell types generated in the neural crest, a paired strip of cells arising at the margins of the neural tube.
Strikingly, d-asb11 transcripts were enhanced in asb11cul mutants compared to wild type, showing expanded expression in the polster, a U-shaped structure surrounds the head [19], and along the margins of the neural plate (Fig. 2B).
In the spinal cord, the roof plate is formed dorsally by the fusion of the 2 lateral margins of the neural plate, whereas the floor plate is induced ventrally by signals from the underlying notochord.
At least in Ce3, the posterior margin of the plate-like neural spine is considerably thicker transversely than the anterior margin.
There is also a decrease in neural foramen size relative to the vertebral body, and a translation of the posterior margin of the body into the neural canal.
The spine projects anteriorly together with the prezygapophyses, exceeding the anterior margin of the pedicles of the neural arch and the vertebral centrum.
The dorsal margins of four isolated neural spines are preserved with rounded quadrangular dorsal surfaces.
