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 a nalyze the temporal and spatial expression pattern of the Pl alpha alp ha-tubulin gene in Paracentrotus lividos sea urchin embryos. The Pl al pha 2 transcript is first detectable at 14 h post-fertilization (blast ula stage) and it is only expressed in the oral ectoderm. The amount o f transcripts of this gene increases throughout development and accumu lates 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. Furtherm ore we have observed the same localization of the Pl alpha 2 transcrip t in the Zn++. or phenytoin-treated embryos, confirming the animal loc alization of the Pl alpha 2 transcript and its specific relation to ne urogenic territory, whose differentiation starts from few founder cell s present at blastula stage.