The proteins of Vent-family and their mRNAs are located in different areas of the tails of Zebrafish and Xenopus embryos.

In molecular embryology, by tacit consent, a presence or absence of the specific mRNA in the cell indicates the presence or absence of the corresponding protein. However, there are lots of evidences that mRNA may be associated with inactive non-translated ribonucleoprotein complexes. Here we for the first time compared the temporal and spatial distribution of the Vent-family transcription factors and their mRNAs in the tails of embryos of two biological species-Xenopus laevis and Zebrafish (Danio reria). We have shown that Xvent-2 mRNA was not active in tails of Xenopus embryos at the early tail bud stage. Although the Xvent-2 mRNA of Xenopus and Vox mRNA of Zebrafish embryos were detected in the tips of the tails, the Xvent-2 and Vox proteins were revealed in other regions of the tails-along axial structures and around somites. We propose that when the translation of masked Xvent-2 (or Vox) mRNA is activated in a tail bud cell, this transcription factor changes activity of target genes. As a result, the cell comes to differentiation.