Large scale EST analyses in Ciona intestinalis: its application as Northern blot analyses

We have conducted large-scale EST analyses of transcripts expressed in the basal chordate Ciona intestinalis. The cDNA libraries examined were from fertilized eggs, cleaving embryos, gastrulae/neurulae, tailbud embryos, larvae and whole young adults, and the gonad (ovary and testis), endostyle, neural complex, heart, and blood cells of the adult. Because the libraries were not normalized or amplified, the occurrence of cDNA clones or EST counts in each library may reflect the quantity of transcripts of the corresponding genes. Thus, comparison of the EST counts of a certain gene at the six developmental stages may reflect the temporal expression pattern of the gene, while the comparison of EST counts in different tissues of the adult may reflect the spatial expression pattern of the gene. Here we present evidence that this is the case, and that the EST count can therefore be used like "Northern blot analysis" of Ciona genes.