Localization of tubulin mRNA during ascidian development.

In ascidians determination of the nervous system is known to occur at the gastrula stage, when the chorda-endoderm and ectoderm come in contact. In situ hybridization with beta-tubulin cDNA showed that tubulin transcripts were concentrated in presumptive neural cells at the early gastrula stage and continued to increase in these cells throughout neurulation. In the young larvae, the tubulin transcripts were also detectable in the adhesive papillae cells, in mesenchyme cells, muscle cells and button cells. The results suggest that expression of tubulin mRNA could be used as a marker for neural determination at early stages and, at later stages, as a marker for all cell types that elaborate many microtubules.