The Vox mRNA and protein expression in zebrafish Pou5f3 MZspg mutant embryos.

The transcription factor of pluripotency Pou5f3 is considered to enhance the Vox expression. This conclusion was based on the study of mRNA expression, but the expression of the Vent-family proteins was not analyzed. We compare spatiotemporal distribution of the Vox and Vent mRNAs and the proteins in embryos of wild type zebrafish (WT) and MZspg (spiel ohne grenzen) mutants devoid of both maternal and embryonic Pou5f3 functions. We revealed the Vox mRNA and its protein in both the WT and mutant embryos during the cleavage period. They were probably prestored maternally. The quantity of the prestored protein, unlike the mRNA, in the mutants was visibly less than that in the WT embryos. The Pou5f3, therefore, had no influence on the Vox mRNA maternal synthesis, but it affected the maternal Vox protein synthesis. During the blastula and gastrula periods the MZspg mutants, but not the WT, failed to synthesize the new Vox mRNA, while the prestored maternal mRNA was gradually degrading. At these stages the WT and mutant embryos displayed minor visual quantitative difference in staining of Vox protein. The Vent mRNA was not maternally prestored and its zygote synthesis slightly depended on the Pou5f3. The Vent protein in mutants and WT was synthesized on the new zygote mRNAs. By the gastrula period, the Vent staining of the WT and mutant embryos were almost comparable. The data obtained suggest the existence of mechanisms sustaining a required Vox and Vent proteins level, but these mechanisms are not directly dependent on the Pou5f3.