Characterization and expression pattern ofpouII1, a novel class II POU gene in zebrafish

POU domain transcription factors that share a conserved DNA-binding domain, POU domain, are important regulators for the development of embryos in various animal species. A novel zebrafish POU domain gene,pouII1 has been cloned. ThepouII1 cDNA is 2080 kb in length and encodes a putative polypeptide of 596 amino acids. It is placed into class II POU family since it shares a high degree of homology with the known members of this family. Northern hybridization identifies a major transcript of approximately 2.1 kb that was present in embryos at the single-cell stage throughout 24 h postfertilization. The whole mountin situ hybridization shows thatpouII1 transcripts are present in the single-cell embryos, strongly suggesting that these transcripts are of maternal origin. During early development of the embryos,pouII1 mRNA was ubiquitously distributed in all cells and tissues. The transcripts are gradually limited to brains and become completely undetectable by day 3. To our knowledge,pouII1 is the first class II POU gene identified in zebrafish.