Alpha-tubulin marker gene of neural territory of sea urchin embryos detected by whole-mount in situ hybridization.

We have used Northern blot and whole-mount in situ hybridizations to analyze the temporal and spatial expression pattern of the Pl alpha 2 alpha-tubulin gene in Paracentrotus lividus sea urchin embryos. The Pl alpha 2 transcript is first detectable at 14 h post-fertilization (blastula stage) and it is only expressed in the oral ectoderm. The amount of transcripts of this gene increases throughout development and accumulates up to the pluteus stage. In this stage the Pl alpha 2 transcript is localized in the neural structures of the embryo. We conclude that the Pl alpha 2 gene is an early neurogenic territory marker. Furthermore we have observed the same localization of the Pl alpha 2 transcript in the Zn(++)- or phenytoin-treated embryos, confirming the animal localization of the Pl alpha 2 transcript and its specific relation to neurogenic territory, whose differentiation starts from few founder cells present at blastula stage.