The transcript coding for an RNA-binding protein is localized in the anterior side of the ascidian 2-cell stage embryo.

We have cloned a putative ascidian RNA-binding protein gene, CiRGG1, which has three RNA-recognition motifs and two arginine-glycine-glycine domains. Its deduced amino acid sequence has a weak similarity to nucleolin, which is one of the known components of messenger ribonucleoproteins. Its maternal transcript is transiently accumulated into the anterior side of 2-cell stage embryos. Zygotic expression of CiRGG1 is strongest in the brain, mesenchyme and endoderm of the trunk region of the tailbud stage embryo. This mRNA is the first example of an anterior-localized molecule in the ascidian 2-cell stage embryo.